scesxixzisz -, h sasaer CORNELL UNIVERSITY LIBRARY Cornell University Library UG447 .P35 + Presentation of the Goodrich-Lakeside Ma 3 1924 030 765 865 olin Overs DATE DUE ,'- (■ t 1' hM— -~ 71 - LP; ■ Tt IS ?.' u L y GAYLORD PRINTEDINU.S.A. K '*& Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924030765865 3?he Good-rich-Lakeside Mask and Carrier I ! Mask and helmet in position PRESENTATION OF T.iE G ODR I C£~ LAKE 3 IDE MASK AND A STUDY OF THE PRINCIPLES INVOLVED IN MASK DESIGN BY MAJOR R. G. PEARGE Medical Division, Chemical Warfare Service, U.S.A. Physiological Laboratory, Lakeside Hospital , Cleveland, Ohio. and W. C. GEER Ph.D. In Charge of Development, The B.F. Goodrich Co., Akron, Ohio. Submitted October 24, 1918. Prepared for Circulation hy The Editorial Section, Research Division, G.W.S. American University Experiment Stat ion . THE GOODRICH-IAEESIDE IULSE TABLE 0? COB TENTS Description of the Goodrich-Lake side Mask 2 Specifications which mast be met by the fighting mask 4 Introduction 10 Primary specification 12. Physiological specifications 12 Breathing requirements 12 Resistance to expiration 14 Dead space 15 Protection of eyes 17 Range of vision 17 Clarity of vision IB Comfort of mask 18 Mechanical specifications 20 Materials of construction 21 Gas tight union 21 Bands and ad^ustms-nt 23 Inhalation tubes 25 Relationship of inhalation tube to clarity of vision 26 Exhalation valve 29 Eye pieces 30 Specifications for carrier and tube 31 Position 31 Tube requirements 34 Service specifications 35 Production 35 Conclusions 37 Analysis of the existing masks 38 Akron Tissot Mask 40 Kops Tissot Mask 45 ■ Zaps Monroe liask 46 Connell Mask 47 Analysis of the Goodrich-Iakeside Mask 47 Exhibits 55 I. The physiological requirements of air for normal respiration under different degrees of exercise. 55 II. The minute volume of air required to meet the demands for very sudden and strenuous work. 57 III. The time relationship of inspiration, expiration and rest to the respiratory cycle, and the effect that resistance to inhalation has on relationship. 58 IV. The effect of resistance to breathing. 60 V. The effect of resistance on the minute volume of air respired. 63 VI. The maximum rates of inhalation and exhalation and the effect of resistance on minute volume of air breathed. 65 VII. The effect of dead air space on minute volume of air breathed. 69 VIII. The harm of dead air space. 75 IX. Measurement of 3.eakage of masks by Pearce-York apparatus. 76 X. Determination of range of vision of various masks. 80 XI. The lake side -Goodrich apparatus for determining the pressures exerted by the bands of the mask. 82 XII. The effect of adjusted masks upon bloodflow in the temporary artery. 84 XIII. Description of the lakeside-Goodrich machine for determining the gas- tightness of a mask irrespective of the face seal. 86 XIV- The Hull method for determining the maximum tension exerted by the harness of a mask. 88 XV. Analysis of bands used in head harness of mask. 69 XVI. Relationship of mask leakage determined by the Pear ce -York method to that determined by the gas chamber tests. 92 XVII. A method of estimating chlorpicrin. 94 XVIII. Description of the Pearce-York apparatus for testing leakage of gas masks. 108 XIX. Comparison of head measurements 109 XX. Pressure of masks. 112 XXI. Effect of changing direction of pull of head "harness. 114 XXII. leak-in of A. T. and Z.T. masks in gas chamber. II? XXIII. Effect of mask resistance to inspiration. 123 XXIV. A comparison of resistances between Geer valves and flutter valves. 126 XXV. Gas-absorption power of A.T. ana juT. face pieces. 146 XXVI. Resistance of corrugated tubing. 150 XXVII,. Rating chart for gas masks. 153 Appendix A - 155 Preliminary survey of the physiological factors which must be considered in mask design and the importance of these factors to the soldier. Appendix B - 187 Field test of the Goodrich Lakeside Masks Index TEA L4K3SIDE-G0 ODRIGH TASPC At the request of Colonel Wm. J. Lyster, Chief of the Medical Division. Chemical Warfare Service, a gas pas 1 : has been designed based upon what are believed to be the correct physiological and mechanical principles. These principles were evolved in a study of the mask made under the direction of Major R.G.Pearce and Dr. \7. C.Geer daring the past four months, at the B.F. Goodrich Company, Akron, Ohio, and the Physiological Laboratory, Lakeside Hospital, Cleveland. Ohio. The mask is offered as one that will eive adequate protection to the soldier under all conditions of military service and at the same time decrease his bodily vigor and efficiency as little as possible. In other worlls, it is hoped that it will prove to be a fighting mask. It is not presented as fulfilling the specifications of an ideal mask, but is presented with the idea that it more closely approaches the ultimate mask than does any other. It is believed that future work must be based on the principles used in the construction of this mask. It was not designed on theories for which there is no experimental evidence, buc is built in accordance with data collected from extensive experimental work done by the Physiological Laboratory at Lakeside Hospital, Cleveland, Ohio, in association with ilo > Development Laboratories of the B, £'. Goodrich Company, Akrr .. Ohio. • 1 , DBSCBIPTIOM Off THa Im ZdS I DE -GOO DRICH M&SK The striking feature of the Lakeside-Goodrich mas* is the incorporation of the head harness support into the mask itself. Indeed it is difficult to describe either separately. It will also he noticed as a radical change that the inhalation tube is carried across above the left eye piece, and enters the mask chamber between the eye pieces, When the mask is adjusted, the close conformity of the mask to the contour of the face and head will be seen. The eye pieces are set close to the eye and at such an angle that they do not act as blinders, but furnish the maximum vision. The face piece clines so closely to the nose and is so formed that air is directly exhaled into the outgoing valve. The adjusted mask elves the impression that it fulfills its duty in the most direct and simple manner , and the incorporation into the mask itself of the head harness gives a uniform and pleasing appearance. A closer inspection shows that the mask is molded from rubber covered with a stockinette fabric. This same fabric extends over the head like a skull-cap. Into it rubber band3 are vulcanized, giving it a binding foroe from before back- ward and from temple to temple, resulting in a uniform pres- sure on the band around the head. Lacings in the stockinette skull-cap permit of adjustment to fit a number of head aisp .: - 2 - The incoming air from the inhalation tube is divide by a piece of thin sheet-rubber cemented into the inside o:c' the face chamber, and results in the air being sprayed ove.? the two eye pieces and so preventing dimming. The Lakeside-Goodrich mask is designed to be used with the Lakeside-Goodrich carrier. In the same way that the mask presents several new and striking features, so does the carrier. The first of these features is that the mask and canister are in separate containers supported by a harness of webbing. The containers are made from a durable duck. That for the mask is in the left infraclavicular region, while that for the canister is over the left shoulder. Both positions are high and of course connected with an in- halation tube over the shoulder* The poeket for the mask is triangular in shape, with the apex directed down and out. The flap of the pocket provides for the escape of the inhala- tion tube. The pocket for the canister is of a suitable size and shape. The two pockets are supported by the harness abort the body, and are so attached that the mask pocket in front may be thrown over the shoulder for an indefinite time. The harness and attachment of the canister pocket are such tha J ; the above condition can be reversed and the canister carrier in front. Further readjustment of the straps permits the carrying of either or both pockets over the shoulder or at the side. The best idea of the mask and carrier is gained from the photograph. - 3 - The Goodrich-Lake side Mask and Carrier The harness is shown in place, and the yoke carrying the mask and canister is held. Note ring in yoke which snaps on to the buckle on left shoulder when yoke is in place. The Goodri en-Lakeside Mask and Carrier The ordinary carrying position. The Goodrich-Lake Bide Mask and Carrier The mask pocket is in the posterior position and is haia there by a strap about the arm. This position does not interfere with the free movement of the arm* The chest is free for carrying sheels, sandbags, etc. The Goodrich -Lakeside Mask and Carrier Back view when the canister is swung to the front. This is the position taken when the pack is being placed on the back. When the pack is on the canister can be again swung back on the shoulder. The Soodrieh-Lakeside Mask and Carrier Back view when the canister is swung to the front. This is the position taken when the paok is being placed on the back. When the pack is on the canister can be again swung back on the shoulder. 4* T *- ■ The Goodrich-Lake side Mask and Canister Side View The Good rich -Lakeside Mask and Carrier Back view with canister on the back The Goodrich -Lakeside Mask and Carrier The canister is shown swung to the front in the position it holds when the pack is being adjusted, or when the hack is wished free. When the pack is on the canister can be swung back on the shoulder. The helmet is shown swung back on the neck as it is when the mask is being put on. When the mask is on the helmet is swung onto the head. In the analysis of the gas mask which follows (p. 47 it will be shown that the Lakeside -Goodrich mask elves adequate protection against gas, and also that this protect!: is secured with a minimum of discomfort. It is proven that the correct physiological, mechanical and production princi- ples are fulfilled. An analysis of the carrier will show that the mask may be carried in an alert position at all times and still not interfere with a soldier's varied work whether he is called upon to carry his pack or shells, to crawl, rest, sleep or fight, or to meet one or more of these conditions at the same time. A brief description of the Lakes ide-Goodrich mask havtru been given in the foregoing resume, it is now proposed to set forth the basic principles which have been evolved in the study of mask design and to show how closely this mask in- corporates them. SPECIFICATIONS MICH MUST BE MET BY THE FIGHTING MA SK A. PRIMARY CONDITION. - The mask must prevent the entrance of air that has not passed through the provided inspiratory passages - i.e., the canister. B. PHYSIOLOGICAL SPECIFICATIONS (p. 12 ). I. Breathing requirements. 1. Resistance to ingress of air must be small at all breathing rates (p. 14 ). - 4 - 2. Resistance to egress of air must also be small at all breathing rates (p. 14 ), 3* Mask must be so designed that the amouiv of expired air rebreathed during inspir ation is as small as possible (dead space) {p. 15). II. Requirements of vision. 1. Range of vision (p,17 ). Nearest possible approach to normal visual field important. 2. Clarity of vision (p.18 ). a. Glass must not deflect visual ray. b. Glass must not dim under ordinary conditions of heat, cold or work. III. Comfort of mask (p.18). 1» The form of the mask and position of its supporting harness must give optimal apposition of mask to face with least possible pressure on pain points or interference with circulation of blood in face and scalp* 2. The boredom of wearing a mask must be minimal, and mask-wearing should be as natural as hat-wearing. IV. Canister (p. 20 )„ - 5 - 0. M3CHANICAI, SPECIFICATIONS (p. 20). The mechanics of the mask must be such that the following essential principles are provided for: 1. Materials of construction (p. 21 ). These materials must be such that while the mask is in service gas cannot perme ate through it. 2. Gas-tight face fit (p. 21). The part of the gas mask in contact witi- the face must be so shaped that the proper physical principles are used to exert the binding force of the bands perpendicularly to the face at each poir^ 3. Head bands and adjustment (p. 23 ). The head harness must give the tension in those directions that permit the face band to be tight with the least pressure on the face. The harness must be capabl of the highest speed of adjustment with- out being thrown out of position. 4. The inhalation tubes (p. 25 ). The inhalation tubes must be sufficient ly large to maintain the resistance to inhalation at a minimum. They must be so placed on the mask in relation to - - 6 - other parts of the mask that the phys- iological specifications will in each case he fully met. 5. Relationship of inhalation tube to clarity of vision (p. 26 ). The entering air must be deflected against the eye pieces in such a way as to remove at each inspiration any accumulation of moisture, and so far as possible the expired air must be pre- vented from passing against the eye pieces and so fogging them. 6. The exhalation valve (p. 29 ). This should have a resistance to exhala- tion corresponding to the physiological requirements of the mask. Resistance should remain as nearly as possible constant at all rates of exhalation, and the valves must be so designed that there is the greatest possible uniform- ity in production. 7. Eye pieces. The eye pieces must be so placed in tb v mask as to give the maximum visual fio> They must be sufficiently close to th= face and eyes to cause the least poss" ble eye strain. They must be connect, . - 7 - with the mask so that they are gas-tiK!. (p. 30 ). D. SPECIFICATIONS FOR CARRIER, TUBS. AND CANISTER {p. 31 ). 1, Position of carrier (p. 31 ). a. Carrier and tube leading from canister to mask must be in a comfortable., con- venient and accessible position, and yet not interfere with the soldier's pack, b. Carrier must be in a position which will interfere but little with any movement of the entire body, c. Carrier must be in a position which will minimize the possibility of injury to mask, tube and canister when soldier is subjected to severe types of work. d. Position of mask and canister in carrier must be permanent, and such that the tier required to adjust mask on face from position in carrier pocket is not greate than six seconds. Mask should be in an alert position at all times. 2. Tube requirements (p. 34). a. Tube must be flexible, non-kinkable and so positioned that there is no sudden change in direction of air current ente ing the mask. - 8 - b.The fixed connection of hose to mask should be as near as possible to the • pivotal point of the neck, and attache to the mask where stresses produce the least distortion to the face piece. 3. Service Specifications (p. 35). Carrier and mask tube must be strong enough to withstand abuse, but not too heavy to give comfort. E. PRODUCTION SPECIFICATIONS (p. 35). 1. Mask must be capable of large-scale production in the factories now available 2. Mask should be so designed that 1% can be made with least possible labor. 3. Design of mask must allow for easy and accurate inspection* 4. Mask must be of such size and shape as to allow for universal fit, 5. Factor of safety in design must be such that the mask need not be rejected for defects other than those which will make it fail to meet the physiological and mechanical requirements of design. F. CONCLUSIONS (p. 37 ), - 9 - Introduction. - In order to design a correct fighting mask, a quantitative study of the forces and materials avail- able must be made. Such a study must consider; (l) the physiological problems involved in wearing a gas mask; and (8) the mechanical elements of design best adapted to meet the physiological requirements. It is absolutely impossible to devise the mask best suited to the functional needs of the body without first estimating the importance of the factors which make the mask a burden. Only by a knowledge of the relative importance of these factors can a mask be designed which will least affect the efficiency of the wearer. An enormous amount of work has been directed towards making a better gas mask. The earlier types of masit did not allow for freedom of respiration and clarity of vision, and thereby seriously decreased the efficiency of the soldier. The cry for some time has been for a mask which protects agaim gas but allows the soldier to perform sustained hard work with minimal discomfort and fatigue. The R.F.K. mask, in all essential principles like that of the British and at present used by our army, requires the soldier to breathe through the mouth, the nose being stopped. The face and eyes are protected by a hood containing eye piece: This mask is uncomfortable, and becomes unbearably so after some time. Breathing through a tube held in the mouth is not a natural phenomenon, and soon tires the soldier. The Chemicr. - 10 - Warfare Service has definitely decide! to adopt a Tissot or nose -breathing mask, and has favorably reported on two such types. The Physiological Laboratory, Medical Division, Chemical Warfare Service, situated at the Lakeside Hospital, Cleveland, Ohio, has undertaken to determine in what ways these masks meet or fail to meet the physiological require- ments of the body, and, if possible, to suggest improvements in the gas maBk. Although the work of the laboratory is far from being completed, certain fundamentals of mass design which bear directly on the well-being of the body have been quantitatively determined and are here reported. Other factors of equal importance, although not yet thoroughly studied, nevertheless because of the exigency of the occasion, are considered, and provisional reports are made. A summary of the conclusions of the investigation is given and recommenda- tions are made. The Development Laboratory of the Goodrich Rubber Company was invited by the Medical Division of the Chemical Warfare Service to cooperate with the Lakeside Hospital Physiol oelcal Laboratory, now connected with the Chemical Warfare Service. Medical Division, to design a mask to fulfill the specifications mentioned in the recommendations. The mask is the joint work of the two laboratories, and is respectively submitted to the Medical Division, Chemical Warfare Service. - 11 - THE PRIMARY SPECIFICATION The primary specification of a gas mask is that it prevent the entrance of air which contains noxious gas into the mouth, nose or eyes. This means an absolutely gas-tight fit between mask and face. This condition has not been obtained up to the present* although it had been generally thought that it was obtained until recently, when it was shown by the Lakeside Laboratory that the Tissot types of mask as now produced do not absolutely prevent entrance of gas-laden air into the mask through the tightness of the face seal. The protection afforded by these masks has been found not to depend entirely upon the efficiency of the seal, but in part upon the absorbing power of the rubber of the mask for the gases in question {Exhibit XXII)- The absorbing power of the mask should not be depended upon to prevent entrance of gas. into the face chamber. PHYSIOLOGICAL SPEC IP IC AT IONS Breathing requirements . - The main object of a mask is to permit respiration of gas-laden air. The mask and canister should be so designed as to allow for respiration with as little variation from the nsrmal physiological con- ditions as possible, but at the same time to afford a maximum protection from noxious gases, To accomplish this, it is necessary that the mask and canister be designed to provide the following: - 12 - 1. All air which enters the mask should come in through the absorbent canister; that is, there must be no leaks at the union of the face piece of the mask with the face (Exhibit XXI). The mask and canister must also allow for the entrance into the face cavities of the mask of at least the maximum flow of air required for work capable of being sustained. Data at the Lakeside Laboratory show that the amount is 45 to 50 liters per minute for maximum sustained work (Exhibit I). Conditions arise, however, when there is a sudden demand for air to carry on extreme exercise for a very short time, and under this latter condition the temporary volume of air may rise to 65-70 liters peyminute (Exhibit II). In normal breathing the inspiratory part is approximately one-third of the total respiratory cycle (Exhibit III). Now. since the amount of air needed for sustained work amounts to 50 to 65 liters per minute, and this amount of air must enter during the inspiratory phase of respiration, which is one- third of the total respiratory eyole. the mask must theoret- ically allow three times 50-65 - that is, 150-195 liters - to enter the mask without appreciable resistance or leakage (Exhibit XXIV). E. The amount of air demanded by the body must pass into the mask with the minimal amounfbf resistance; that is, the resistance to ingress of air must be as small as possible at all rates of breathing. The great resistance which is - IS - encountered is due to the canister. The canister is a necessary evil, and probably can nev «r be so designed as to offer a small resistance and yet givt protection* The resist- ance of the tubes and canister to respiratory action can, however, be diminished by proper attention to mask design. The importance of resistance to breathing lies in: (1) the effect on the circulation of the blood, and (2) the changes in the lung tissue, which seriously interfere with the gas exchange between the outside air and the blood. Data have been presented in previous reports (Appendix a) to draw attention to the seriousness of resistance to inspiration (Exhibits 17 and V). In these reports it was suggested that the deleterious effects on the body consist in changes in the blood pressure, increased work of the right side of the heart, and an increase in the blood and lymph content of the lungs* Resistance also decreases the minute volume of air breathed and thereby increases the percentage of carbon dioxide in the expired air (Exhibit XV). The foregoing changes are all deleterious, and their pathological significance has been pointed out in previous reports (.exhibit V). Although the chief problem of resistance in gas mask design concerns inspiration, nevertheless resistance to expiration is an important factor. The expired air of the lung contains carbon dioxide for which means of escape must be provided. The expiratory act is more passive than the inspiratory act, and resistance to expiration is. therefore, - 14 - more keenly felt that resistance to inspiration. It is then imperative that the exhale valve be so arranged as to allow for the escape of the entire amount of air during the time of expiration with the least possible resistance. The data of the laboratory indicate that seldom, if ever, do expira- tory rates rise above a velocity of 150 to 175 per minute (Exhibit VII. - "The maximum rates of inhalation and exhala- tion, and effect of resistance on minute volume of air breathed." )► The effect of resistance to exhalation upon the vital organs of the body is not dissimilar to that of inspira- tion f Exhibit IV. - "The effect of resistance to breathing."). When the mask is in adjustment with the face, a chamber is formed between the face proper of the mask and the face itself. This chamber, into which air is exhaled from the mouth, and into whieh fresh air is brought by the tube from the canister of the mask, forms a part of the so-called deadj space . If the face -piece of the mask is so designed as to trap more than a minimum amount of expired air, it defeats the physiological purpose of respiration, for this expired air contains carbon dioxide which the body is excreting as a harmful substance. This trapped air is undesirable in two way;. (1) It may be rebreathed at the beginning of the next inspira- tion, since it is the nearest air to the respiratory passages: or (2) the face piece of the mask may be so designed as to allow this expired air to diffuse with- the fresh incoming air. - 15 - Under either of the foregoing conditions carbon dioxide will be taken into the lungs with the expired air, and previous data have been given which show that carbon dioxide in the inspired air causes an increased minute volume of respiration {Exhibit VII), Mow, again, since the life of the canister depends on the amount of gas-laden air pulled through it, it is essential, from the standpoint of the life of the can- ister and from the physiological standpoint, that the mask be so designed that the face chamber be as small as possible, and also that during expiration there be as little mixing of the air issuing from the nose and mouth with the air which remains in the upper part of the mask. Egress of air from the nose and mouth should, therefore, be very free, and not give rise to the eddy currents which could cause a mixing of the expired air with the air of the mask- From the above discussion it is seen that there must be an intimate relationship existing between canister design and mask design; that is, if a high canister resistance is neoessary to give protection, it is, therefore, all the more necessary that the mask be gas-tight at all pressures, that at higher suction pressures the resistance which the mask offers to ingress of air be less, and that the free chamber or dead space of the mask be still further reduced in order that the total resistance may be minimum (Exhibit VIII}- - 16 - Although the chief function of the mask may be said to be to protect the soldier from inhaling poisonous gases, of only slightly less importance is t he protection of the eyes from irritating gases while yet allowing for maximum vision. If the nose-breathing, mouth-breathing mask: of the Tissot type is adopted, it is necessary to incase the eyes in the same chamber as that used for egress of air, unless separate partitions are made between the oral and nasal openings and the eyes. For numerous reasons this is impos- sible. The chief reasons are: (1) the comfort of the mask, and (2) the fact that air must be drawn across the eye pieces of the mask in order to prevent dimming. In regard to the relationship of the mask to vision, two problems must be considered: (1) The range of vision . - Unimpeded vision allows for sight in the horizontal plane at an angle equivalent to more than 100 degrees; in the vertical plane, it is, perhaps. about equal to an angle of 138 degrees. For a fighting mask this range of vision should be approximated as closely as possible. Vision directly ahead may be all that is required for trench warfare, artillery work, marching, etc., but for fighting the greatest range of vision possible is essential. Probably from an evolutionary standpoint, the great range of vision which we have developed was primarily for protective measures, and certainly in modern warfare, in which even the - 17 - most primitive kinds of weapons are used, normal vision should be approximated (Exhibit X). (2) Of no less importance is clarity of vis ion . The eye glass used must be of a quality which will not deflect the visual ray. By this we mean that the glass must not be wavy. Another very important problem in gas mask design is to prevent the collection of moisture on the eye piece. With the British mouth -breathing type of mask, the eyes were simply incased in a hood and the expired air never collected was in the mask; therefore, the air in the mask/relatively dry. On the other hand, with the Tissot mask, air saturated with moisture at a temperature higher than the atmospheric air is being continuously driven into the mask. This moisture-laden air collects very quickly upon the radiating surface of the eye piece and dims it. Numerous anti-dimraing substances - that is, substances which when rubbed on the glass will pre- vent dimming - have been used with partial success. However, in the Tissot type of mask they are not uniformly successful, and it is the general trend of opinion that the current of air entering into the mask should be directed against the eye piece so as t o remove whatever moisture is collected on it, and prevent the further accumulation of moisture. In other worSs^ it is necessary to prevent this vapor in contact with the eye piece fr.om ever reaching the dew point- Comfort of mask . - The comfort of the mask is probably of only slightly less importance than the respiratory function - 18 - and the visual properties. Unless the mask be so comfortable that it does not seriously interfere with the well-being of the soldier, the man will hesitate to wear it at times when he is in doubt as to the actual danger involved in not wear- ing it. It is, therefore, very essential that the mask be so designed as to give the maximal degree of comfort. To this end the mask must have the seal against the face so placed as to prevent undue pressure on the sensitive points of the face and scalp (Exhibit XX), or interference with the circulation of the blood in these parts (Exhibit XII). The face is probably one of the most sensitive portions of the body, and the pain points over the face and scalp are ex- tremely sensitive. For this reason there should be studies made to give the form of the mask and the position of the supporting harness the maximum efficiency in giving a tight seal with the least possible pressure on the face (Exhibit XI), If this pressure is evenly distributed over the entire surface that seals the mask to the face, it will not only give a better fit of the mask to the contour of the face, but will prove more comfortable. Uniform pressure distributed over an entire surface will not be so painful as extreme pressure on one point, and it will be better borne by the wearer. In this connection an apparatus has been devised to measure the uniformity of pressure in masks (Exhibit XI). Another factor which is closely related to the comfort of the mask is the boredom which prevails while wearing it. - 19 - This boredom is due to the sense of heat on the face, the drawing feeling of the bands, the moisture accumulating on the face, etc. It should be the aim of the mask designer to produce a mask so comfortable that, if a man was educated to wear it, it would be as natural for him to do so as it is to wear his hat. Such a condition can be obtained provided the mask has a maximum degree of comfort, good range of vision and little interference with the respiratory .phenomena* Canister . - This study does not include the canister, but it should be mentioned that the nature, amount and dis- tribution of materials in the canister must be such as to remove the gases from entering air without disturbing the physiological principles above discussed. MECHANICAL SPECIFICATIONS The physiological requirements of the mask must be reflected in its structure and design. In order that this may be properly done, the closest cooperation of physiological and mechanical experts is necessary. Every feature of the design and material used in the mask must be correlated to the physiological requirements of the mask. Following out this principle, the mechanical specifications here reported take up pointed point the physiological specifications de- tailed above. In order to provide against the entrance to the lungs of air that has not passed through the canister, proper attention must be paid to: - 20 - 1 - The materials of Qonstrw^. . Thege raat erials must be such that while the mask is in service gas cannot permeate through it to an extent sufficient to produce a physiological effect. When out of action the materials must permit a fairly rapid evaporation of the absorbed gas. The work already done in the laboratories of the B.F.Goodrich Company has shown it possible to procure relatively imperme- able materials. Any joints made by the fabric and metal parts of the mask, such as the eye pieces, exhale valve, and entering air conduits, must be gas-tight. In order that the efficiency of all joints may be determined easily, simple means of inspection and testing should be provided. These unions should be made so simple that visual inspection will be sufficient to detect any gross irregularity or defect. Mechanical means should be provided to determine whether or not the mask is gas-tight without reference to the face seal. Such a device has been devised by the Lakeside Laboratory and the Goodrich Development Laboratories. This device can easily be made to serve as a final testing machine in the production department manufac- turing the mask. (This machine is fully described in Exhibit XIII). 2. In order to secure a gas-tight, union between the face and the mask, it is fundamental that certain physical principles be observed. If these principles are neglected. it will be impossible to fit a large number of faces. - 21 - fa) It is of greatest importance that the gas-tight fit of the mask be obtained by so designing the bands and harness of the mask that the seal is secured by two funda- mental bands. One of these should lie in the region of the forehead in approximately the same plane as the hat band when on the head; the other should pass under the chin and around the dome of the head directly in front of the ears and thus lie at right angles to t he other binding band. If these two bands are properly adjusted, they will lie in regions of the face where they will cause a minimum amount of discomfort to the rearer (Exhibits XY and XX). (b> These binding bands must be supported on the face and head by means of flexible straps or belts which go around the head in direct continuation of them. When the bands are thus tensioned approximately at right angles to each other, there can be little or no distortion, since the band is flex- ible and, therefore, can have no torsion movements. If these bands pull in directions so that they make an acute angle to Bach other at the top of the head, there will be a tendency to buckle and a constant leakage of air into the mask at the buckling of the band. (c) The face band part of the mask must be so con- structed that at each point on the band there will be pressure applied perpendicularly to the face at each point. If the face were a sphere, or if each surface of the face under the - 22 - bands were made up of convex surfaces, then the bands with their head straps would exert a pressure inward parallel to and approximately inversely proportional to the radius of curvature of the convex surfaces. Since^ however, in the region of the temples many faces are flat or concave, it is obvious that there will be no pressures exerted by the bands at these points because of the fact that a flexible member pulled from two ends of a flat or concave surface can exert no pressure inward on the surface. In order therefore that the face piece may be formed so as to approximate a universal fit (namely, exert pressure inwards upon the flat or concave area of the face), it is necessary to construct the head band so that the tensions upon the two fundamental bands are upon a high point on the band which will tend to press in a low point of the band inwards towards the face. Several methods can be used to accomplish this end. One of them is to use slightly stiffer rubber in the band surface inward at these areas. The tension upon the more flexible part of the band around these areas will then depress these stiffer curved surfaces inward toward the face- 3. The bands and adjustment . - If the adjusting bands and the harness are arranged in the manner above recommended, it would be -possible to produce a gas-tight fit with the least possible pressure. Care should be taken that the pres- sure of the band across the forehead does not unnecessarily - 23 - press on the nerves and blood vessels supplying the scalp* Such important points lie above the eyes near the bridge of the nose and along the side of the forehead about half an inch in front of the ears. Tension under the chin is undesirable. The Lakeside Laboratories have devised a method of determining the irressure necessary- to produce the optimum fit. (This method is fully described in Exhibits XI and XIV). The harness holding the mask to the face should pro- vide fo^ (1) the holding of the mask to the head, and (2) the binding tight of the bands of the mask to the face to secure pas -tightness. It has been found, however r that masks, although tightly adjusted to the face, have small leaks as determined by the Pearce-York apparatus (Exhibit XX), although the men wearing them were not gassed when exercised in gas chambers. Experiments were then conducted with a view to showing the relationship between leaks as determined by the Pearce-York apparatus and by the gas chamber test. The results show that a mask may have a certain leakage as determined by the Pearce-York apparatus and yet afford protection in gas chamber: (Exhibit XVI). It is important to note that, as found in the experiments described in Exhibit XVI, some masks with the largest quantitative leak-in gave the greatest protection in the gas chamber. This means that some other factor than tightness aids in gas protection (Exhibit XVI). ~ 24 - The forces which provide for gas-tishtness should be utilized for supporting the mask, because any force which tends to displace the mask on the face should not directly affect the band provided for gas-tightness. For the same reason preat care should be taken to provide that the bands of the' harness be maintained over the scalp in exactly the position intended. The present type of harness is extremely hard to adjust in a hurry; and men with experience in placing the mask on the face have difficulty in adjusting the band to erive the optimum pull. The mask can be best supported to the face and the proper lines of tension best exerted by using individual straps for support and tension (iSxhibit XV). It is, therefore, suggested that these bands be vulcanized into position in a cap, which can be pulled over the head easily, and which when in position vill automatically place the bands in the proper position.. Such an arrangement, besides living the -Drotection desired, will also allow the mask to be adjuster' in the briefest period of tiae. 4. Inhalation tubes . - The inhalation tubes must be sufficiently large to maintain resistance at a minimum, or in other words, large enough so that the relationship of velocity of air through the tubes approximates in linear proportion the pressure under which the air is delivered. Moreover, in order to protect the mask from being displaced on the face, the entrance of the tube leading from the can- ister to the mask should be placed so as to allow for the - 25 - freest movement of 'head witfc-'&eeaT Movement of the tube.. This consideration is of .utmost ii .pittance, because of the vital necessity of maintaining a close apposition' of 'the mask to the contour of the f acV to prevent leakage. The least movement of the neck is in the. middle of the cervical vertebrae and the most convenient point nearest to this place for fixa- tion of the entering tube from the carrier would perhaps be in the region of the mask below the ear* Taking this position as a point of fixation, we must now consider the optimum point of attachment of the inhalation tube to the fa^ce piece proper of the tube. 5. Relationship of inhalation tube to the clarity of vision . - Experience has shown that it is necessary to have incoming air deflect against the eye pieces so as to remove what moisture may have collected upon them during expiration and to prevent as far as possible the formation of this mois- ture. It is, therefore, necessary to consider this feature in placing the entrance of the inhalation tube. There are three possible places for air to enter the mask and still permit the current of air to be directed against the eye pieces. They -are t 1. Directly below the eyes. 2. Between the eyes. 3. Directly above the eyes. If the air is taken below the eyes , it necessitates the making of a "V" in the tube in order to direct the air - 26 - against both eye pieces. If this "7" is placed inside the mask, it increases the dear air space (Exhibits ¥11 and VIII). If it is Placed on the outside of the mask, it increases the weight of the mask on the face and introduces mechanical and manufacturing difficulties. If the air enters between the eyes , the eye pieces must be rather far apart, which interferes with vision. This position, however, has the advantage over the entrance of air below the eyes, since it obviates the difficulty of two entering or clarification tubes as in the first possibility. The principle of air entering between the eyes is used in both the Miller and the Kops masks. If the air is to enter above the eyes , it is possible to have an entering tube go up between the eyes and open with a Y tube above both eye pieces, or to bring the inhalation tube to the mask above the left eye pieee and let it enter directly over the bridge of the nose. In this latter arrange- ment a suitable baffle plate directs the current of air against the eye pieces. For the following reasons, this last method is preferable to all other methods. (a) The entering tube is attached to the mask at the point of its firmest fixation to the face, and the bands of the mask at this point are aided in their support by the weight and fit of the trench helmet. (b) The entering tube can be devised so that it does not interfere with vision and does not cause discomfort to the temples and forehead. - 27 - (c) The air entering the ma.sk can be drawn over the entire field of the eye piece, and there is no need of a baffle plate of such a size that it interferes with vision. Whatever method is adopted to provide for entrance of air into the mask and its direction against the eye pieces, one important factor must be considered: viz,, to prevent the accumulation of moisture-laden air thrown out of the lungs at expiration upon the eye piece of the mask. The problem is not, as it may at first appear, to prevent expiratory air from entering this space above the nose, but rather to direct the outgoing expired air away from this space without preventing the entrance of a small amount into this area. J?or example, if the negative inspiratory pressure amounts to a minus pres- sure of 4 inches of water, the return of the pressure to normal, together vith a four inch positive pressure, would account for an 8 inch pressure (the addition of a negative 4 inch pressure to a positive 4 inch pressure). Sight inches of water pressure is equal to 15 mm. of mercury, which is 2% of the normal atmospheric pressure. There exists, then, only the possibility of the entrance of 2jo of moisture-laden air into every cc.- of dead space. This shows that if a means is provided for the escape of expired air without setting up eddy currents, there is "out a small possibility of the air in the mask about the eyes having a humidity great enough to cause dimming through the collection of moisture on the eye piece. - 23 - The problem is now simplified, since it is not to prevent by an air-tight partition the entrance of air from below upward, but to prevent the setting up of eddy currents by the outgoing expired air, The proper placing of a low resistance exhale valve in a chamber that will direct the air downward and out, and still allow for an easy, comfort- able adjustment to the face below the eyes, has been found to accomplish this (Pearce and Hull deflector). If this principle is adopted, the outgoing air will be deflected from the eyes and dimming reduced. The use of a baffle plate to prevent eddy currents is a theoretical possibility which must be experimented with to determine its practicability. The difficulty of design and manufacture are great. 6. The exhalation valve . - The exhalation valve must be so constructed as to allow for the escape of the entire amount of expired air during the time of expiration and with- out resistance. This means that the valves must be so de- signed and be of such a size as to provide for the maximum velocity rate of expiration, which has been found to be 200 liters per minute. •' There should be low resistance, because resistance would cause a bac£ pressure, which, no matter how small it might be or how momentarily it might act, would set up eddy currents, causing a diffusion of the moisture -lad en expiratory air into the comparatively dry air about the eyes, and resulting in dimming of the eye pieces. Resistance to expiration -would defeat many physiological requirements. - 29 - The valve must not only allow for the escape of air without resistance, but must be so simple that its mechanical- ad- justment is so positive as to prevent a leak-in under any conditions, and it must maintain its adjustment without care on the part of the wearer. The valve must allow for escape of air without any fluttering, because fluttering is not only an extremely disagreeable sensation to the wearer, but tends to encourage leaks by jarring upen the parts in contact. It also causes increased resistance to escape of air, and gives; rise to eddy currents* The valve must be stout and durable, rugged and capable of production in quantity. ?• The eye pieces should be so designed and positioned as to give the mqximum vision. They should be of such a size and shape as to secure" the desired vision, but must conform to their location in the mask. The lens of the eye piece must meet all demands of vision and remain non-shatterabie. The entire eye piece must be so designed as to be capable of rapid production, and allow for easy inspection. The inser- tion must be leak -proof . The present eye pieces in themselves perhaps answer all general requirements, but the manner of their insertion should be improved, leaks about their insertion not detected by inspection alone have been found by the soap bubble test. The eye piece should lie as near as possible to the eyes, and encroach irooa the lower and lateral field of vision to a much less extent than in the present Tissot type. - 30 - SPECIFICATIONS FOB CaR3IER *LW TUBE Position . - Carrier and tube leading from canister to mask must be in a comfortable, convenient, accessible and alert position, and yet not interfere with the soldier's pack. To meet these conditions the carrier must be placed within an arc described by the movement of the arms. The mask must be reached by a movement that is simple, quick, and accomplished without exertion. In order to be convenient and accessible, the carrying position must be as near as pos- sible to the position of the mask in use. To permit the quickest adjustment, the mask should also be carried in such a position that it is not folded in any way. Folding not only causes delay in adjustment, but increases the wear on the mask. The carrier must be in a position which will allow for sny movement of the entire body, .aside from the physiological reasons for absolute freedom of movement, it is obvious that a soldier must be allowed unlimited body motion. It would be extremely unwise to limit any motion whatever, for it is impossible to Know all the extreme positions in which he may be placed. The carrier must also be in a position which will minimize the possibility of injury to the mask, tube and can- ister when the soldier is subjected to severe types of work. One object desired in any mechanical device subject to wear is endurance, and a mask is a life-saving device which must - 31 - undergo the severest cf harlsiijs incidental to a soldier's work and yet be in so perfect a condition at all times that the soldier may rely upon it to save his life. Ho time is given in a gas attack for inspection and repairing. Prom the discussion of the foregoing conditions, it is seen that the placing of the carrier is of utmost import- ance. The general positions in which a carrier may be placed are: Front, back, side or a combination of two or more of these places. Front position : Advantages. 1. It is close to position of use* 2, There is space in this area. Disadvantages. 1. If high enough to be close to position of use, it is not accessible. 2. If low on thorax, it limits motion, loses the value of being close to position in use, and requires long inhalation tube. 3. Limits downward vision. 4. Limits motion of arms. 5. Weighs on thorax in breathing. 6. Is awkward in appearance. 7. Does not permit of crawling. Back position : Advantages. 1. A secure position. 2. Natural area to carry weight. 3. Freedom of movement. Disadvantages. 1. Area needed to carry pack. 2.- Distance from- -position to use. 3. In crawling, catches on wire, etc. - 32 - Side position : Left side preferred, because majority have greater dexterity of right hand. Advantages. 1. Accessibility. Disadvantages. 1. Distance from position in use. 2. Insecurity. 3. Limitation. on motion. 4. Interference with walking. 5. No natural body protection. 6. Tires arms. 7. Same disadvantage as front. Combination of positions : In discussing the use of two or more areas for the carrier, it is necessary to discuss the possibility of carrying the mask in a area separate from the canister but of course always in direct connection with the canister through the tube. This form of carrier, first developed in the laboratories of the B.F.Goodrich Company in June. 1917, while it allows for compactness of each part, ffives a more equal distribution of weight. The mask proper miRht be in a convenient, accessible, alert position, and yet permit the bulkier part containing the canister to be in a better carrying position. It is also necessary to keep the inhalation tube connecting the mask proper and the can- ister as short as possible. Considering the necessity of a short tube in connection with the other factors of accessibility, convenience and security, it would seem that the best locations would be hiffh up on the left shoulder and back, with connecting tube over the shoulder. The canister carrier, being the heavier and bulkier part, could be carried in the region of the left - 33 - shoulder. Here \* would have all the advantages of the back'"'' position with none of the disadvantages., for the canister in its special carrier would he small and compact enough so that it would not interfere with the pack. Then, again, if the mask was placed in front on the left side below the collar bone, it would be in a convenient, secure and very accessible position. Because of the high position of the canister and mask proper, the tube need not be of ereat length. Thus all the desired conditions of accessibility* alertness, convenienc as d security would be met without interference with the pack or any limitation of motion. The non-interference of the carrier with the pack can be accomplished by hinging the canister pocket to permit the canister to be loosened and thrown over the left shoulder in front while putting on the pack. The canister can then be returned to the original position and securely strapped. Tube requirements . - The tube must be flexible, non- kinkable. and so positioned that there is no sudden change in current entering the mask. A stiff, non-flexible tube would not allow quick adjustment, nor adapt itself to the various positions required by a fighting soldier. V,hile it is desirable to secure utmost flexibility and adaptability, the tube must/ be so constructed as to permit kinking, which would, of course, defeat the purpose of the mass to deliver gas-free ait inside the mask. The tube must be so placed and made that movements of the head will not change the - 34 - direction of the air current in a manner to increase the. resistance to air passing through it. The weakest points in. the air-tight passage formed by the tube from canister to mask is the connections. The junction to the mask, therefore, should be as near as possible to a fixed point* Less movement would not only result in less strain upon the connection, but would also lessen the danger of diminishing the air current by a narrowing of its passage through folding or pressing in of the mask on the tube, which could result with movement of head in the extreme positions. Service specifications . - Both carrier and tube must be made of materials stroma' enough to withstand abuse, but not too heavy for comfort. The material must be good, enough to meet the requirements demanded of it. but need not be of such a character that it would outlast the other parts used in connection. Material in excess of the foregoing specifi- cations would be a needless waste of labor and expenditure of money. Present material is satisfactory as to durability and weight. Production . - Any mask to be adapted for use must be capable of large-scale production with the present available material and machinery. Mask making on a large scale is a new industry, and manufacturers have but recently been able to se- cure the necessary machinery and material to bring production up to the point of beginning to supply the demand. It is obvious then that, under the present exigencies, any new mask desie-n must fit in with the present plane of production. - 35 - The mask should be designed so that it can be made " with the least possible labor. Machinery and material are not alone necessary for production; trained labor is a very important factor in quantity production of any article. Un- fortunately, even the time element does not permit of an increase in number of workers; under the present conditions the reverse is true. Therefore, any mask to be satisfactory from the standpoint of production must minimize labor. The design of the mask must be such that a simple. • quick, and accurate inspection can easily be made. The great number of masks passing through production makes an elaborate inspection by complicated tests impossible, but because of the very nature of the work for which the mask is designed, the tests must be accurate and defects in production easily detected. The mask must be so constructed as to allow for a fit as nearly universal as possible. If production is to be as rapid as desired, it will be of ereat assistance to have the smallest number of sizes required to fit all heads. With this end in view, measurements were ta&en of certain diameters and circumferences of the head in the case of a large number of subjects (Exhibit XIX). It was found that, by constructing the head harness of an elastic material, it would be possible to secure a fit for almost all heads by making the mask in three different sizes. - 36 - The factor of safety in design must be such that the mask neeci not be rejected for defects other than those which will make it fail to meet the physiological and mechanical features of design. The mask suitable for quantity production must be so designed that minor defects in structure which do not in themselves weaken the mask or render it unservice- able for use, will not cause it to be rejected. This means that the design of the mask must provide for a factor of safety which is great enough to allow small changes in the position of the head harness » eye pieces, position of entering and exit tube, etc., etc., without altering the efficiency of the mask. In the past one of the serious troubles with the Tissot type of mask has been to meet quantity production with- out a serious number of rejections. If the fit and structure of the mask are so delicate that small deviations from the specifications cannot be made, quantity production can never be obtained, and the cost of the mask will be tremendously increased. CONCLUSIONS AS TO TIE DESIRABLS MaSK From the above discussion it is concluded that the ideal mask should allow for normal physiological breathing and normal vision, and produce no discomfort to the wearer. It should be made of materials which are easily ob- tainable and relatively impermeable to ?as. It should be provided with a gas-tight fit on the face, and be easily adjusted. - 37 - The inhalation tube should offer no resistance, and be TJlaced so as not to impede the movements of the wearer. The exhalation valve should be stout, durable, and have a minimum resistance to exhalation; and should absol- utely prevent the entrance of air into the mask. There should also be a means of preventing dimming of the eye pieces. The eye pieces should allow for normal vision. The carrier should be in a comfortable, convenient and aeeessible position, and should allow for all kinds of military work. The mask should, be strong enough to stand all normal abuse incident to military life. It should be capable of large-scale production with the least labor, and it should allow for simple and accurate inspection. Now that the principles of mask design- have been given, and the reasons why it is believed that these principles are fundamental have been set forth, it is proposed to make ANALYSES OF THE EXISTING MASSS based upon the principles taken up in the foreeroing discussion, and to show in what way they fulfill or fail to fulfill these fundamental conditions. An analysis of the Lakeside-Goodrich mask is g-iven, together with evidence which it is believed will prove that it more closely approaches the ultimate mask than does any other. - 38 ~ AHALX3IS OF jSXISTING MASKS Following our entrance into the war, the American forces were issued British masks,, and this mask was soon put into manufacture in this country. The mask as made in the United States differs from the English mask in no way except that it is a more finished product; there is no im- provement in the essentila features. The mask is known in this country as the R.F.K. mask (using the initials of the it men who put/into manufacture). This mask satisfies the breathing requirements of the soldier in a simple direct manner, but because of its discomfort it has always been unpopular., and the service has definitely committed itself to the use of the nose-breathing mask of the general type first used by the French and called the Tissot mask. The three types developed by the Gas Defense Service along this line are known as the Akron-Tissot, and Kops- Tissot and the Kops-Monroe-Tissot. These masks are now in production, and it is understood that they will be used by the men at the front within a short time. This paper under- takes to make a critical analysis of these masks from the standpoint of the physiological, mechanical and production specifications, and in an entirely impersonal manner to grade the masks by a fixed scale, based on the relative importance of the different specifications which a mask should have, as pointed out in the foregoing discussion. - 39 - THE AKR0N-TIS3OT MaSF In the analysis of the Akron-Tissot mask, we will consider four points: (1) its gas-tightness on the face; (8) its conformity to the physiological specifications; (3) to the mechanical specifications; and (4) to the production specifications mentioned in the foregoing study. LEAKAGE The variation found in the leak-in of the Akron-Tissot mask on various faces is rather great. The lowest leak-in with a four-inch suetion pressure we have found to be 7S c.c. per minute. In spite of this leakage the mask protects, in part because of the absorptive power of the rubber for gas (Exhibit XXV). FROM THE STANDPOINT OF LEAKAGE, THE AICRON-TISSOT MASK IS UNSATISFACTORY. PHYSIOLOGICAL SPECIFICATIONS A large resistance to inspiration is not offered by the Akron-Tissot mask at low velocities of air. When large volumes of air are breathed, as during exercise, the resistance is tremendously increased. This is due to the shape and size of the clarification tube and to the constricted opening of the aluminum casting. THE RESISTANCE OF THE AKRON-TISSOT MASK TO INSPIRATION IS ENTIRELY TOO LARGE TO PERMIT SUSTAINED VIGOROUS EXERCISE. The resistance to exhalation in the Akron-Tissot mask is in part due to the flutter valve (Exhibit XXIV}. The new - 40 - Akron lis sot Mask, Front View Akron Tlssot Mask, Side View No. 5 Flutter valve is an improvement. Its resistance to exhalation is. however, several times greater than that of the improved Geer valve. HOTS: The flutter valve resistance is so great in some cases that in expiring the air passes about the face seal, THE EXHALATION RESIS'lAMCE OF THE aKROH-TISSOT MASK IS LARGER THAU IT MEED BE, AMD THE EXHALATION VALVES LEAK. The dead space of the Akron-Tissot mask is compara- tively low. and in our series varies between 125 and 285 c.c, the respiratory efficiency ranging from 60 to 80 per cent. THE DEAD SPACE OF THE AKRON-TISSOT MASK IS COMPARA- TIVELY LOW. Vision . - The range of vision of the Akron-Tissot mask is entirely too small. It should and can be made much larerer. The lateral and downward vision is very much reduced, being less than one-fourth of the normal (Exhibit L), Clarification . - The clarif ice t ion tubes of the Akron- Tissot mask provide for fairly efficient removal of any mois- ture which may accumulate on the glasses during expiration. The prevention of dimming t however, is probably only a theo- retical possibility. Comfort . - The pressure required to produce a tight seal in the Akron-Tissot mask is too great for comfort (Exhibit XX). The lack of good vision, the tightness of the sealing bands, the sense of having something attached to the - 41 - face and body which restricts the movement of the head, and the fact that the carrier is held on the chest in a rather awkward position - all contribute a distinct element of bore- dom to the wearing of the Akron-Tissot mask. MECHANICAL SPECIFICATIONS The materials used in the construction of the Akron- Tissot mask are satisfactory. The method of producing a gas-tight fit in the Akron- Tissot mask is absolutely wrong on basic principles. The head harness is arranged in such a manner that the mask is pressed against the face instead of having its sealing bands bound to the face, as pointed out in Exhibits XV and XXI. Because of the improper head harness, the pressure required to make a tight seal is in excess of that necessary to insure a tight seal were the forces applied in the proper manner (Exhibits XX and XXI). The head bands used in the. Akron-Tissot mask, being made of elastic tape, seldom, if ever, occupy the same posi- tion on a man's head when he puts on the mask. For this reason, unless great care be taken in adjusting the harness there can be no certainty of having a tight fit of the seal- ing bands against the face without some buckling about the edges- THE HEAD HARNESS OP THE aERON-TISSOT MASK IS WRONG IB PRINCIPLE. - 42 - The opening in the aluminum casting for the inflowing air is entirely ;oo small for high velocities. Moreover, the shape and sire of the clarification tubes cause the re- sistance to inspiration to mount very high when volumes of air such as are breathed during strenuous exercise are pulled into the mask (Exhibits XXIII and XXIV). Because of the high velocity of the air passing through these tubes., the anti- dimming qualities of the mask are very good, but to provide for anti-dimming at the cost of so much resistance does not appear to be a correct principle. The exhale valve is the common flutter valve, which is attached to the aluminum casting and protected by a wire guard to prevent its striking the chest. The valve has some leakage, is in great danger of being struct, is apt to get flirt into the T>arts. and has a rather high resistance (inhibit XXIV), The -position of the eye pieces in the Akron-Tissot mask is without question very bad. They project from the face too far, and lateral vision is obscured by a blind, as it were. The manner of attaching the eye pieces to the mask is also not very satisfactory, and in many of the masks we find evidence of small leaks about the eye. CARRL3R AMD TUBE The bag, hanging at the side of the body under ordinary conditions, and carried high up on the chest when the mask is worn, as is the case in the carrier of the Akron-Tissot mask, is decidedly inconvenient. Freedom of body movements - 43 - can not "be had with this arrangement. The feeling of a tube projecting in front of you and connected with the chest, is uncomfortable. One cannot crawl on his stomach or hands and knees without risk of injury. The mask is not in an accessible position to put on in case of gas alarm* The tube connecting the canister to the mask is attached to the mask at a point where small streams tend to produce relatively large changes of position on the face- The length of the tube and direction of air through the tube are rood points, making the resistance of the tube to inspiration small. The carrier is relatively easy to make, and has wearing properties. THiS CARRIER IN THE aKRON-TISSQT MASK IS INCOHViSBIiSHT INACCESSIBLE, AND UNCOMFOR TABLE AND IT HINDERS THE BOD? MOVE- MENTS. TEE DIRECTION Of THE INFLOMNG AlP. IS DIRECT AND TEE SIMPLICITY AND WEARING QUALITIES OF THE MaSK ARE ADVANTAGES. PRODUCTION The Akron-Tissot mask could theoretically be produced in quantity by the existing machinery of the country were it not 'for the fact that its design is so improper that slight deviations from the specifications cause the mask to be re- jected. A mask of this type properly designed and manufactured would offer absolutely no problem for quantity production. - 44 - THE kops-tissot mask Since the paramount specification of a gas mask is that it prevents the entrance of gas-laden air to the chamber about the eyes, nose and mouth, a gas mask which fails to come up to these specifications is not canable of being analyzed. We have found the Kops mask to have a very high leakage even a$ low suction pressures, (Exhibit XXI). Moreover, we have found that the apparent protection which is afforded by a Kops-Tissot mask is due to the absorptive property of the rubber of the mask, (inhibit XXV}. The wide face band, fitting snugly about the face, although it allows the entrance of air to the mask through the tiny passages which must be present between the face and the band (Exhibit XVI) protects the wearer from gas because of the rapid absorption of sas by the rubber of the band. In other worcts, the Kops mask acts as an auxiliary canister. If such a principle is adhered to, provisions must be taken to in- crease the absorptive power of the band of the mask so that this protection may be greater. The principle is wrong, and the Kops mask is condemned unconditionally for this reason. There are several other points in the Kops-Tissot mask which are bad: it has a large dear air space (Exhibit VII); the binding force of its bands is not properly directed, being the same as in the Akron -Tissot mask (Exhibits XV and XXI); and its resistance to exhalation is relatively high (Exhibits XXIII and XXIV). It has one or two good points: its resistance to inhalation is small (Exhibits XXIII and XXIV); and it is fairly comfortable. The materials used in the Kops mask are not satisfactory - too much fabric and too little rubber; in order to get gas protection, therefore, the mask is heavy. The manufacturing methods for making proper rubber face pieces are well developed in a great number of factories in this country, and the necessity of a faoric face piece, which is expensive and undesirable, we believe no longer exists. THE KOPS IvLaSK IjEaKS IJS SPITE OP ALU TENSION V/EICH UaY BE PUT UPON ITS BAUDS (EXHIBITS XX aHD XXI). ITS MANUFACTURE SHOULD v THEREFORE, 33 STOPPED IMMEDIATELY. - 45 - Kops Tissot Mask, Jfront View Kops Tissot Mask, Side View THE MORRIS «!»» CO- WASH.. D. C THE gOPS-MOflRQj MA SK During the course of this study a new type of mask was submitted to the laboratory for examination , known as the Kops-Monroe mask. This mask was brought forward because of its ease of manufacture, It being made out of a flat piece of rubber so cut that, when certain edges were sewed together , a very satisfactory face piece was obtained. Standard fitting, for flutter valve and hose and the clarification baffle plate used in the Zops mask were employed in this mask, and a harness similar in principle to that used in the Kops-Tissot and Akron-Tissot masks was used. PHYSIOLOGICAL SPECIFICATIONS The time was not available for the complete study that was made of the other masks. From the data at nand» however, the following conclusions may be drawn: The dead space of the mask is somewhat less than that in the Akron-Tissot mask. The resistance to inspiration likewise is somewhat less than in the Akron-Tissot mask. This is due primarily to the fact that the entering hole through the aluminum casting has been enlarged. The vision is slightly better than that found in the Akron-Tissot and Kops-Tissot masks. The pressure on the face necessary to make a tight seal is the same as that found in the AKron- Tissot mask, and in spite of any pressure that might be put on the bands, it was found impossible to make an air-tight fit as tested by the Pearce-Yoric apparatus. A very serious attempt was made to improve this mask so as t o decrease the dead space, decrease the dimming, and increase the gas-tight- ness. It was not possible to improve the mask materially except in the matter of applying the principles of harness design, the details of which were given in a previous part of this report, and which have been used in the French mask. By placing a sort of cap over the head to which is laced the elastic harness in such a manner that the pull is made in a plane directly about the horizontal diameter of the skull and in the vertical plane of the head, as indicated in the figure - 46 - Kops Monroe Mask. Front View t Honna tetebs co., *wh., d. t Kops Monroe Mask, Side View following Exhibit XIV, it was found that the pas-tightness of this mask: could be very much increased with an absolute deorease in the pressure exerted on the face. This fact is sufficient to warrant more intensive work being directed towards the development of the harness in the case of the Kops-Monroe mask. This mask because of its ease of manufac- ture is superior to the Akron-Tissot mask. Prom the physiolog- ical standpoint, however, there is little, if any, improvement THE COMSLL MASK A mask developed by Major Connell has been exhibited here. It has not been possible to make any detailed phys- iological examination of this mask. However, the harness used in this mask, although improved somewhat, is wrong in principle. The dead space apparently is rather larger than is necessary * The manner of producing a tight seal against the face is clever and has many good points; it appears to be a distinct improvement in this regard over the existing types of mask. Further development of this masic is recom- mended. ANALYSIS OF LAKiiSIDE-GOODRIOH MASK The mask in some points resembles the Akron-Tissot mask. As in the Akron-Tissot, there is a rubber face piece, and the seal between the face and the mask is made by the pressure of rubber against the face. The design is, however essentially and fundamentally different from that of the Akron-Tissot mask. The seal of the mask is maintained by a txroper head harness so that the lines of force used in seal- ing the mask to the face are fully utilized (Exhibits XV, XX and XXI). There can be no displacement of bands over the - 47 - scalp, since these bands are incased in a light skull-cap, which automatically places the hands in the proper position. The binding band of the mask has been so designed under the chin and on the cheeks that a maximum seal is provided for with a minimum amount of pressure (Sxhibit XI). Details have been worked out for the production of a tight seal across the t enrol es of irregular faces by the use of a semi-pneumatic pad in the temporal region, which produces a tight seal on such faces* PHYSIOLOGICAL SPECIFICATIONS Breathing requirements . - The entrance of air into the mask is provided for by a corrugated tube coming up over the back and side of the head across the left eye and entering the mask between the eyes, from which the air is dispersed over the eye pieces by means of a deflector* The position of the tube is such that movements of the head tend to cause distortion of the binding forces of the mask to the least possible extent * for the point of fixation of the entering tube is at the point of intersection of the horizontal and vertical binding forces, Moreover, the trench helmet acts as an additional anchorage. Since the mask is designed to be worn with the Goodrieh-Lakeside carrier, the entrance of the air from the side is feasible. During inspiration the air is drawn from the entering tube between the eyes across the eyes and into the nostrils, there being sufficient room between the nostrils and cheeks and the mask to allow for the - 48 - entrance of air without resistance (Exhibit XXIII). The exhalation valve is so placed that a breath is blown directly out. The mask is so constructed in this region that there are very few eddy currents set up, so that moist air is pre- vented from going into the eye chambers of the mask, and dimming is thereby reduced. The exhale valve has been pre- sented to the Gas Defense Service by Dr. W.C.Geer, and in its present improved form as now presented it does not leak at suction pressure; it is compact; it is assembled at its point of manufacture; and it is easily inserted into the mask. Its resistance is several times less than that of the best flutter valve (Exhibit XXIV). Its compactness is also greatly in its favor. Dead air space . - The effective dead air space of this mask has been reduced to a minimum f in the tests conducted ranging between 25 and 55 c.c. The effective ventilation of the mask, therefore, is about 90>. In this respect it is about 100$ better than the Akron-Tissot mask (Exhibit VII). Vision * - The position of the eye pieces on the mask is such that a very large field of vision is obtained, being about 100% greater than that of the latest Akron-Tissot mask (Exhibit X). Its clarity of vision is equal to or better than that of the Akron-Tissot masK. Dimming does nccur at low tempera- tures during expiration, but this dimming is relatively slight., and in the majority of our tests has been less than that - 49 - experienced in the Akron-Tissot mask. Comfort . - The comfort of the mask depends primarily on the tightness of the seal band. Gas-tightness can be ob- tained in the case of the Goodrich-Lakeside mask at pressures far below those which are necessary in the Akron-Tissot mask to produce a seal which is still much less effective (inhibit XX). The absence of projecting tubes from the front of the face, the great range of vision f Exhibit K) , the small dead air space {Exhibit VII), the neatness and dressiness of the mask - all contribute toward making the boredom of wearing the Goodrich-Lakeside mask less than in existing types. MSCHaMCaL specifications The material which is used in the Akron-Tissot mask can be used in the production of this mask. The gas-tight face fit is properly shaped so that the correct physical principles are used to exert the pressure of the band per- pendicularly to the face at all points (Sxhibit XV). The head harness is so positioned that its tension gives a tight seal of the mask to the face ?/ith the least possible pressure (Exhibit XX). The ease of adjustment of the harness permits the mask to be put on in half the time of the Akron-Tissot mask, and when onee on it is less easily displaced. The in- halation tubes are large enough to maintain the resistance to inspiration at a low level - about 50$ less than in the Akron-Tissot mask at 85 liters per minute. The Lakeside and Goodrich laboratories will decrease the inhalation resistance - 50 - to a point where it approaches that of the Kops-Tissot mask. Time alone has prevented this from Toeing accomplished at this date. The anti-dimming properties of the mask are fairly good. More exhaustive studies are now being made on this subject, and assurance is ^iven that improvements are in si^ht. The exhalation valve gives a wider rubber to rubber contact that does the flutter valve, and it opens with many times less resistance and stays open with many times less pressure than does the best type of flutter valve (Exhibit XXIV). It is a positive-closure valve. It is easily manufac- tured and assembled. The position of the eye pieces on the mask erives maximum vision (Exhibit X). Carrie r a nd Tube The Lakeside-Goodrieh carrier and canister allow for a comfortable, convenient and accessible position. In iorty seconds of time, with an hour's training, the carrier can be Tout on, the mask adjusted to the face, the helmet donned and the nack -cicked up from the ground and settled for marching. The carrier position allows the mask to be taken from its pocket and put on in two seconds. The pockets for the carrier and canister are attached to the harness and the harness so well arranged that the can- ister and mask can be carried in a variety of positions, and - 51 - not interfere with the regular .soldier" s pack. This is of advantage, permitting the canister and the carrier to be in a convenient^ accessible, secure and fully protected position and yet not in any way interfere with the soldier's work. If it is desired to have the chest free, the mask pocket in front may be thrown over the shoulder and fastened j yet with the mask in this position it requires but one second longer to adjust it than from its regular position in front, flow, if it is desirable to free the back from any incumbrances, as in crawling through barbed wire, when it is easier for the soldier to protect his front than his back from objects which are impeding his progress, the canister may be used in a front position, which is much more convenient than the posi- tion now used. This position allows for immediate adjustment of the mask. If it is desired to free both the back and the front, the mask and canister may be carried at the side. In fact the carrier is so designed that it will allow for universal adjustment according to the needs of the soldier during work, rest and sleep. The carrier allows for the use of the mask and canister with the pact or independent of the pack. This of course is an obvious advantage. The pockets are made of durable duck and the harness is made of one-inch . webbing with rings and snaps, This allows' for a simple, light harness capable of quick adjustment to the variety of position- and the pockets afford a secure protection for the mask and canister. There is no reason why the canister can not be used - 52 - with any kind- of mas* if the en be M 1:3 tuba is properly arranged to allow for side entrance. PRODUCTION As far as our study has gone up to the present time, it is certain that the Goodrich-Lakeside mask can be produced in accordance with the general work ox the Akron-Tissot mask. with the exception that several operations now practiced in the Akron-Tissot mask can now be omitted* It will require nothing more than new forms and other minor equipment. The same trained labor can produce this mask. On account of its simplicity of design, it may be possible to considerably speed up production over the Akron-Tissot mask. Inspection . - In view of the fact that the Goodrich - Lakeside mask is properly designed in accordance with the principles necessary in a mask, dimensional variations may be considerably larger than in an Akron-Tissot mask, and the inspection may be reduced to the determination of tightness and general appearance, with, of course, measurement within considerably leeway. This mask wil^permit of correct manufacture with dis- tinctly fewer inspection operations, lower inspection cost, and a much higher percentage of perfect masks. ^'.hile at present our investigations have not proceeded far enough to give accurate figures, there is proof that the Lakeside-Goodrich mas.i will cost less than the Akron-Tissot, this saving being largely because of its great simplicity, the fewer operations in the manufacture, aad the low inspectioi cost, SUMMARY In the study of gas masks certain principles have been evolved which have been proved to be fundamental. In the Lakeside-Goodrich mask there is presented a mask that meets these requirements - physiological, mechanical and production; and in the discussion of this mask evidence is eiven that it more closely approaches the ultimate mask than does any other. - 53 - RSCCMMiiHDATIOJK Since from a physiological, mechanical and production standpoint the Lakeside-Goodrich ma&k is at every point superior -to the existing masks so far as our tests have gone, it is recommended that this mask he immediately pro- duoed in quantities sufficient to determine its manufacturing possibilities and its availability by actual field tests. - 54 - EXHIBIT I THE PHYSIOLOGICAL REQUIREMENTS OF AIR FOR NORMAL RESPIRATION, UNDER DIFFERENT DEGREES OF EXERCISE Apparatus : (1) A mouth pieee: soft gum rubber used in R.F.K= masks. (2) Valves: Pearoe gut-valves, made of pig gut, which automatically partition the inspiration from the expired air. Very sensitive to low pressure. Give highly satisfactory results* (3) Tissot spirometer: an aluminum ball suspended between the double walls of a hollow cylinder. Water fills the space between the walls of the hollow cylinder, thus acting as a seal for the bell. An opening at the bet torn of the cylinder connects through a three-way stopcock with a rubber tube to the expiratory valve. The bell is counterpoised by means of a weight. A math- ematically constructed compensating wheel counteracts the de- crease in the buoyant force as the bell rises* On top of the spirometer Ere inserted a water manometer and a stopcock with a tube for drawing samples of the expired air. A stirrer is also inserted in order to insure representative samples. A scale on the side of the instrument drives the volume of air. (4) Treadmill: a movable sidewalk. Gives speed up to 7<5 miles per hour. An electrical device for measuring distance travelled. Accurate to thioee feet. (5) Necessary accessories: (a) Electrical device for determining respirations; (b) Kymograph; (c) Haldane gas analysis apparatus; (d) Time clock which records time in seconds electrically. - 55 - Procedure, : The sublet first adjusts himself into respiratory equilibrium by breathing from the outside air. The valves are -then adjusted so that the expired air is passed into the spirometer for a definite .length of time. At the end of that period the valve is again turned to connect the subject with the outside air. After reducing the volume of exhaled air to normal temperature and pressure, the volume was recorded. Results* From the experiments performed in these laooratories, it is found that the physiological requirements of air for different degrees of metabolism are as follows.: Condition Mln imum vol. in liters Maximum vol. in liters Average vol. in liters At rest ■5.0 9.. 5 6-. 7 Walicing miles per hour 15 . 5 22.0 18 ..0 Running 5,4 - 5.7 36.0 45.0 40.0 miles per hour 56 - EXHIBIT i: TH3 MIJWT3 VOLUME OP ..IR REQUIRED TO MjSST TE3 DSviAWpS FOR V3RY StDDSH AND STRENUOUS WORK The volume of air required by the individual under these conditions is greatly increased. In subjects so far studied in this laboratory, we have found that minute volumes as hiffh as 80 to 90 liters of air are obtained during maximum physical exertion. Such physical exercise can, however, be maintained for only a very brief period of time. - 57 - EXHIBIT III THE TIME RELATIONSHIP OF INSPIRATION, EXPIRATION AMD REST TO THE RESPIRATORY C]fCLE, AND THE Ee'PECT THAT RESISTANCE TO INHALATION HAS ON THE RELATIONSHIP. Apparatus : Two horizontal-swine check-valves (Plate I) working alternately. Proper connections to the plate of these valves record the positive and negative pressures and the period of rest which constitute the respiratory cycle. This cycle is described on a moving smoked chart. A Jacquet chronometer records the time in fifths of seconds. Procedur e ; The subject breathes through connections until respiration appears normal. The pointers on plates of check valves describe the events of respiration on the moving drum. Prom these tracings and from the chronometer the de- sired data are obtained. The length of respiration and rest after inspiration, and the length of exhalation and rest after exhalation, were obtained in a series of observations. Prom these data the average time of each individual phase was estimated and expressed in percentage of the total cycle of respiration. - 58 - Df/t&ntfw >?r THe HOMZONTXLrSMNG CHECK V/?LV£S i/S&X) iN gSTflBi-SSHIN® TH& TiM£ f*£.i-ATlQNSH IP S£TW£.£N THE. 7*t//)S£$ P LATr- |75£*/-/ea4'« 1h woe^-yO'ece "vN Poiriiot'.- Tf&aoras ■more me, rp% e»^ f o/ veJvt-s plajfie, - strfu ptufayy / Pwrftee:- ' 7t*catds \ ^ =N I l S ! y y CONDITIONS OP jjK?j£?IMj3ET R3ST W4LZIUG RUNNING Resist- Resist- ance in ance in inches of inches water breath- of water ing 85 L/M Resist- ance in inches of water Inhalation 28.6 34 36 47 33 41 51 Rest after inhalation 11.8 10 7 ifehalation 47.3 45 57 53 56 59 49 Rest after exhalation 13.0 11 7. .7 4 Conclus ion : The results show that res is tan ce to.. inhalation alters to a marked extent the time relationship of the events of the respiratory cycle. With a 4 inch resist- ance measured at 85 liters flow of air per minute, the in- spiration occupies 28.6 per cent of the total time of the respiratory cycle, but we find that there is an increase in the amount of time taken for the inspiratory phase in walking and running. This increased time of the inspiratory phase is also directly in proportion to the amount of resistance. It is known (Exhibit 7} that the inspiratory phase has a definite effect upon the blood pressure, the mass movement of the blood, the work of the right side of the heart, the gaseous exchange between the blood and air of the lung, and the lymph and blood content of the lung; and since breathing against resistance lengthens the inspiratory phase, the above changes would be operative over a greater period of time. - 59 - EXHIBIT IV THE iSFF^CTS OF RjJSISTaiJCE TO BE^ThlNG General ,c ons iderat i ons :• 4ir normally enters the lungs because of the negative pressure developed within the chest during the expansion of the thorax at the time of inspiration. Under ■ohysioloe-ical conditions, the negative pressure rarely exceeds 1 to 2 inches of water,. for- the air passages are so constructed as to off er-. the- minimum resistance. The addition of a mask and canister through which air must be pulled in inspiration will-, qf course,, cause an increased resistance to the entrance of air,. and' this must he overcome by an increase in the negative pressure in the thorax during inspiration. Such a condition has effects upon the heart and lungs, which can be summarized as follows; Effe ct of increased negative pressure on the blood pressure : Increased negative pressure would cause mors blood to enter the lungs during inspiration. This increased volume of the bloody being pushed down into the left- side of the heart during the early part -of inspiration, increases the mass movement of the blood and tends to increase the pressure of the blood, iSffect of i n creased negative pressure on the right sid e of the heart : The blood pressure in the pulmonary arteries rarely exceeds 50 mm. of mercury, which is equal to about 20 inches of water.. The right ventricle and auricles of the heart are thin-walled, and will, undoubtedly, react to slight - 60 - changes In pressure. If breathing is accomplished against inspiratory resistance, the negative pressure developed in the thorax is opposed to the pressure developed in the chambers of the heart. Accordingly, if the same volume of blood is maintained during the inspiratory portion of the • respiratory cycle while breathing against resistance, the chambers of the heart must exert a pressure equal to what they normally exert plus the additional negative pressiire. This additional negative pressure has little effect upon the left side of the heart, where the pressure is habitually high; besides, the walls of the left side of the heart are thick and accustomed to high pressure. In the case of the right auricle and ventricles, however, when the resistance to inspiration is great the additional load may have a marked effect, as was shown by Dr. C,F, Hoover twenty years ago in some experiments which he did on the changes in the second sound of the heart when inspiratory efforts are made with a closed glottis. He found that there was always a split in the second sound, and interpreted this as meaning that there was a delay in the contraction of the right ventricles owing to the increased work which it had to do to overcome the negative pressure of the thorax. We know that the right side of the heart, as compared with the left, is not built to stand severe strain, and under increased negative pressure the extra work thrown upon the right side of the heart may dilate it. - 61 - Effect of negative pressure u pon the lympji_and blood content of the lungs . - Dry cupping is a recognized medical procedure. It consists in placing a cup over a portion of the body and withdrawing air from the cup, thus creating a partial vacuum in the cup. This causes an in- creased flow of blood into the area covered, as is mani- fested by redness of the skin. If maintained for any length of time, it results in an exudation of lymph into the tissue from the. blood, minute hemorrhages, and a swelling. A sim- ilar condition may result in the lungs when breathing is accomplished against a higher inspiratory resistance. This would result in an increased negative pressure, which, actiru on the lung tissue, would cause the same condition as dry cupping of the skin. The lung membrane, which is purposely thin to permit an easy exchange of gases between the inspirec air and the blood, would become infiltrated, swollen and covered with lymph and blood exudate, and its respiratory function would thus be seriously impaired, - 62 EXHIBIT V EFFECT OP RESISTANCE OK THE IIFJK VOLUME OP AIR RESPIRED Apparatus : See Exhibit I. Method ; The minute volume of the respired air was determined by collecting it into a spirometer in a known time under conditions of walking and running. The volume of ex- haled air, after being corrected to normal temperature and pressure, was measured. Resistance to inspiration was intro- duced by having the subject breathe through canisters of known resistance of 1 inch, 2 inches, 3 inches and 4 inches measured at 85 liters per minute and water pressure. Uet result was expressed in per cent decrease in minute volume of air inspired. Observations: Walking: Subject 1 Liters per min. Subject 2 Liters per min. iiverag CO2 in pired : e 'jo ex- air Average y£> decrease in min.vol. Bo resist- ance 19.5 18.6 4.5 1" it 18.3 19.0 4.6 2.0 2" ?i 17.9 16.9 4.8 8.7 3" ii 17.6 16.3 5.0 11.0 .4" ii 17.4 15.4 5.2 14.00 - 63 - Running Subject 1 Subject 2 Average u /o Average J Jo Liters Liters C.Oo in ex— decrease in per mir. per min. pired air min, vol. No resls :t- 37.2 ance 1" n 35.0 2" ii 34.9 3" ii 32.7 4" n 30.4 39.6 5,2 35.0 5,5 8.7 35.5 5.6 10.8 33.. 4 5.8 13*9 32.3 6.0 18.4 Remarks: '"hen resistance is introduced, there is a tendency on the part of the subject to make an increased effort to breathe- Unless this is guarded against and the subject breathes normally, there may at first be a slight increase in volume of air breathed. Conclusions -. Resistance to inspiration decreases the minute volume of air inspired, which., of course, results in an increase of carbon dioxide in the blood. - 64 - ezhib.:t vi maximum ratjs op inhalation and exhalation and effect of resistance on minute volume of air breathed. Since it is very desirable to icnow the maximum velocity of the air entering the mast during inspiration and exhalation., in order that the mask and canister be designed to give the flow of air necessary at any degree of exercise, the following experiments were made: Method : Two Venturi meters were so arranged that the speed indicators registered on the smoked drum of a kymograph. The time was recorded by a Jacquet chronometer. The experiment were performed at rest, walking 3»5 miles an hour, and running 5.5 and 6.5 miles an hour, while the subject was breathing ae-ainst a resistance of 0.42, 2.42 and 6.42 inches of water, with a standard air flow of 85 liters per minute (pressure taken at the mouth). Results : The results tabulated below are the average number of determinations on different individuals. The minute volume of air actually breathed under various conditions is given, with the maximum velocity rate of air flowing into the mask and out of the mask during inhalation and exhalation respectively. It will be noted that breathing against resist- ance gives an appreciable decrease in the minute volume of air breathed; also in the maximal velocity rate of air entering - 65 - into the mask. On ths other hand, the rate of exhalation is somewhat increased, as breathing is accomplished against a resistance. The maximal velocity rate of inhalation re- corded when the subject was running 5*5 miles per hour was 213 liters per minute. \.e have never found the velocity ratf- of exhalation to exceed 800 liters per minute. We have very good reason to believe that it seldom reaches this figure. Table Maximal velocity of air entering the lungs at various levels of work and various inspiratory resistances . Condition of Resistance Minute Maximum Maximum experiment to inhala- volume velocity of velocity of tion inches in inhalation exhalation water liters Liters/ruin. liters/min. At rest 0. .42 9, .5 28 15 2, .42 20 17 6, .42 10 20 Walking 0. .42 23< ,5 59 43 3.5 M/hr. 2, ,42 22. .1 53 43 6c ,42 18, ,8 42 47 Running 0. .42 50 96 87 5.5 M/hr. 2, .42 46. 6 82 91 6. .42 41. i f 77 101 Running 0. 42 65. ,4 132 110 6.5 M/hr. 2« ,42 62, ,3 128 118 6. ,42 53. 5 76 128 Running 0, 42 213 6c 5 M/hr. 2. ,42 198 (Forced res- 6o 42 140 piration) - 66 - Su mme ry The above results indicate that the maximum velocity of air passing through the canister and into the mask would not exceed at the most a velocity of 100 liters of air during work which is capable of being sustained for any period of time. At levels of exercise above this, as when running at the rate of 6.5 miles per hour, the maximum breathing rate of inhalation in the series did not go above 138 liters per minute. When a forced respiration was made at the end of the runnine\ a velocity of 215 liters of air per minute was ob- tained; the maximum rate of exhalation at this time was not recorded, but could not have been more than 200 liters T>er minute. It is unnecessary to test the resistance of the ex- halation valve at velocities of more than 200 liters of air per minute. The maximum velocities of inhalation even under forced conditions do not go above slightly more than 200 liter; per minute. Since this velocity is seldom obtained, it would seem more rational to determine the resistance of the canister and mask at lower velocities of air. Probably 150 liters of air per minute would be an optimal maximum velocity. In Pl&tes II and III we have attempted to show the effect which resistance has upon the velocity of air and the volume of air which is bei ng taken in during any period of the respiratory cycle while the subject is breathing against no resistance and against 6 inches resistance. The abscissas give the time in seconds and the ordinates the velocity of - 67 - WH/IT KES/ST/INCE TO iNHALATWN TO THE GESPlR/ITOfiy CYCLE PLATE II POES No tesi^fknci 6" r»$/sihnce Z 3 7~ I ME — "» plate r r r DOfS ro thje *e jESje/ze^ro/? y cycle Mo Kesisto/ice flow in lifers per minute. Since velocity multiplied by time erives volume,., the space inclosed "by the curve above the abscissas gives the volume of inspiration and that below the volume of expiration. The two volumes do not differ greatly. Any small variations which occur are simply due to errors in plotting the curves. - 68 - EXHIBIT VII EFFECT OF DEAD AIR SPACE OH MI2JUTE VOLUME OF AIR BREATHED Tills Exhibit discusses the following subjects: (a) Effect on breathing through tubes of known dead air space. (b) Effect on minute volume of respiration when breathing through various typeB of mask. (c) The Lakeside-Lewis method for measuring the dead air space, or the effective ventilation of the lungs when wearing a mask. (a) Effect on minute volume of air breathed when respiration .is accomplished through tubes of actual known dead air space . - Different lengths of glass tubing (15 mm. bore) were connected between the mouth pieces and the valves. The volume of these tubes and the actual dead air space actually represent the volume of expired air which must be rebreathed at each inspiration before fresh air can be drawn into the lungs. It will be noted from the following table that, when respiration is accomplished through a tube having a capacity of 587 c.c, the minute volume of air is increased S5fo at rest; 45$ when walking; and 19% when running (Plate IV) (b) The effect on the minute v olume . of breath through masks having different dead air spaces . - The volume of air breathed at rest, walking and running, under exactly the same conditions as were present in the foregoing experiments, - 69 - ;-jt : ( " • v - *,---; ~-S? . n "t /* (■ ■ „• :» i jj S* «B was determined when the subject wore a Goodrich-Tissot mask, a Zops mask and a Connell mask. It was found that the vol- ume of air breathed when the subject wore a Goodrich-Tissot corresponded to the volume of air which he would be expected to breathe were he breathing through a tube having a capacity of 822 to 275 c.c. (Plate V). Table Condition of Dead air Minute Increment Per cent experiment space volume over no dead increase Liters air space At rest 0{ valves) 5.8 .0 — 127 7,8 2.0 34,4 260 9,2 3,4 58.7 387 9.6 3,8 65.5 WalEing 21.5 ,0 — __ 3.5 miles 127 25.6 4.1 19.1 an hour 260 29.1 7o6 35.3 387 31.2 9.7 45.0 Punning 40.5 .0 — ■■ 5.5 miles 127 41.3 0.8 2.0 an hour 260 48.3 7.8 19.3 The percentage increase in the volume of air breathed when respiration is accomplished through a mask over that which the subject would reach without the mask, might be called the known effective or wasteful proportion of respira- tion due to the dead air space. In other words, it coiald be called the net dead ai£ space of the mask in contradis- tinction to the actual volume of air which is present in the - 70 - l» i - : i?'; 1 '!!/•■' face piece of the mask, which ii the foregoing experiments, in the case of the Goodrioh-TIe set. amounted to about 500 c.c. The effect of the resistance of the mask in decreasing the minute volume of the air was not taken into account in the above experiments. It is, therefore, very probable that the effect on the dead air space in the above cases as found by this method would actually be less than what was present. For this reason another method for determining the effect- on the daad air space of a mask was devised. ( c ) The Lakeside-Lewis Method for Determining Dead A ir Snaoe . - Principle of Met h o d; At the end of each expiration the mask contains a certain amount of expired air containing carbon dioxide. At the end of the inspiration the mask con- tains less of the expired air and therefore less carbon dioxide. If the volume of carbon dioxide which the mask contains at the end of expiration and at the end of inspira- tion, and the average depth of each respiration , and the estimated amount of carbon dioxide expelled from the mask at each respiration be determined, it is possible to estimate exactly the volume of carbon dioxide which was taken into the lungs during an inspiration and to compare that with the volume of carbon dioxide actually expelled from the mask. Since it is the function of respiration to keep the percentage of carbon dioxide in the lungs constant, the carbon dioxide inspired must be diluted by a sufficient volume of air to - 71 - lAKES/PE- LEWIS METHOP FOK PBTERMINING^ P£AP At* SPACE m Mf1SK$ PLATE VI Spirometer -&- C O-p €S.C t"tu 60O® CvC- KfQQh lrt*r -c- Soo c.&- ~.«~»»j j&e//&w* keep the percentage of aarbon dioxide in the lung air un- changed. Taking advantage of this principle, the following apparatus was devised and the procedure attempted: Apparatus and Procedure : The subject at first breathe room air through an intake valve, and exhales through stop- cock 7 or 8 (Plate YI). A newspaper or book will act as an aid for establishing equilibrium in the subject's respiration. It is first necessary to determine the subject's volume of a normal expiration. This is accomplished by having him male a number of expirations into spirometer B. This air is sampled and analyzed. The next step is to find the composi- tion of the air in the mask before and after inspiration. To do this the subject breathes 500 c.c. of fresh air from spirometer C. The subject holds his breath while the air in the mask is forced out with the foot pump into spirometer A. Stopcocks 4, 3, 2 and 7 are shut off, and enough air is pumped through the mask to give a total volume of 2500 c.c. The same procedure is followed after a normal expiration. The air is sampled and accurately analyzed. From the results thus obtained, the physiological dead air space may be calcu- lated, as well as the amount of carbon dioxide carried! back to the lungs with each respiration. It was found that on an average there was 11.2 c.c. less carbon dioxide in the Akron-Tissot mask at the end of inspiration than at the enfl of expiration. In the case of the PIotos mask, this amounted to 16.8 c.c. In the case of - 78 - the Geer model, it amounted to 6 c.c. If we assume that in the average expiration of 500 o.c, having an average carbon dioxide percentage of 4 per cent, there is about 20 c.c. of carbon dioxide given off at each expiration; then in the case of the above mask we shall find the following amounts of wasteful or extramural ventilation due to the dead air apace in the mask. Or, expressed in coefficient of effective ventilation, we might take the reciprocal of the amount of carbondioxide which had to be expired from the lungs in order to get the required amount of carbon dioxide out of the mask. In the above case we find the following: Geer • • • • 77 gops • » • • 54,5 A.T. « • 4 » 60 This method of determining dead air space is much more accurate than the one first described, for with it the question of reduction in the minute volume of respiration due to resistance is not present. The volumes of air obtained are, therefore, hieher than those obtained in the previous metho& 4 Tabulation of the net d ead air space , or efficie nc y of ventilation of go ps , ikkron-Tissot and Geer Masks . The calculation of the extramural or wasteful venti- lation is carried out as follows: If 25.0 cc« of COr, are given off at each expiration, then 500 X 26 * 650 - 500 = 150 cc t extramural or wasteful 20 ventilation. - 73 - Type of mask Geer mask, approx. Sept. 1 model KT mask, approx. Sept.l, model. cc. GOp given off at each expiration 26.0 Extramural ventilation cc 150 Old type deflectro 36.5 420 A.T. mask, approx. Sept.l model 31.2 280 K.T.M. mask, submitted Oct. 11, fabric rubber binding 23.25 81 K.T.M. mask, submitted Oct. 11, fabric binding 24.5 112 K T mask, submitted Oct. 5 27.75 193 Goodrich Lakeside mask submitted Octt 21 22.24 56 A.T. production mask, submitted Oct. 11 25.00 125 The VENTILATION EFFICIENCY of the masks would there fore be as follows: Geer Submitted about Sept. 1 77% Kops ! 11 t» 54.3$ A.T. t ii n 60jt> K.T.M. K.T.M. K.T. ' Oct, 11 (rubber binding) ' Oct. 11 (fabric binding) ' Oct, 5 85.2% 81 . 65b 72.1^o A.T. Oct. 11 80/ Goodrich-Lakeside ' Oct. 21 89% - 74 3XEI3IT VIII HARM OF D3AJ) AIR SPaCS In Exhibit VII we have given conclusive proof that the minute volume of the ventilation is influenced in a marked degree by the dead air space of the mask. The harm of the dead air space of the mask lies in three things: (1) To ; have the minute volume of air increase, it Is necessary that the partial pressure of carbon dioxide in the blood leaving the lungs be increased. This amounts to partial asphyxia. (2} It has been shown in j&hibit IV that the resist- ance to inspiration has a deleterious effect on the normal physioloery of man. Since the resist- ance which is offered to the air flowing through the canister is proportional to the increase in the dead air space of the mask, an increase in the dead air space of the mask amounts to the same thin? as an increase in resistance of the canister- Any reduction in the dead air space, therefore, amounts to the same thing as decreas- ing the resistance of the canister; or since canister resistance is necessary for protection, any reduction in the dead air space will allow for increase in the resistance of the canister. (3) The life of the canister depends on the amount of gas -laden air which is pulled through it; and since the presence of the dead air space requires a larger minute volume of air to be breathed, it follows that the life of the canister is proportionally decreased. In the case of the Kops mask," it would be reasonable to expect thet, while the suoject is at rest, there would be a 45 per cent decrease in the life of the canister; in the A. T. a 40 per cent; and in the new Geer model a 2,6 per cent decrease. - 75 - EXHIBIT IX VALVE LEAKAGE: A COMPARISON OF TH3 LEAKAGE OF THE FLUTTER VALVE WITH THAT OF THE GOOLRICH-LAKESIDE TYPE OF VALVE Object: To determine the leakage of the flutter type of valve and the Goodrich-Lakeside type of valve under varying conditions. Observations : The leakage of the Goodrich-Lakeside valve, after 64 hours of continuous use, was determined with normal setting of valve, and then with different degrees of compression, with the idea of determining what degree of compression or extension would produce the optimum results. The mounting of the valve was arranged so that by simply turning a milled screw the degree of compression could be obtained. Table 1 Vacuum maintained #1/20 Leakage in terras of c.c. air per min. One valve only tested in each case. ValVes tested dry. Valve Setting 6 Y ' 4" 2" T I' 2 1.3 2.1 2.6 1.1 1.3 8.0 2.7 1.7 6.5 7.8 7.2 Goodrich-Lakeside 7/8" Normal 5 slim wall after 64 hrs. fatierue Compressed 1.5 o05 " Compressed 34.2 .10 " Extended 4,1 .05 " Extended Leaked at all vacuums .10 Ho. 5 Flutter valve ? 389* 300* 400* after 64 hrs. fatigue *Leakage so rapid that dependable readings of present apparatus could not be taken. Wetting valves did not help. - 76 - Heat reduces the life of rubber* By placing rubber in a warm oven for a period and then testing it, it is founc that the rubber has changed in exactly the same way as age changes it. The rubber industry know what amount of heat and what length of time in the heat will change rubber to the same degree as age will chanee it. The Goodrich-Laicesidc valve after being in the life oven one day showed the results given in the following table. Table 2 Valve Setting 6" 4 « 1" Lakeside-Goodrich 7/8" normal slim wall after 1 day in I if e oven Compressed .05 Compressed .10 ,3x tended .05 Extended .10 1.3 1.6 3.4 2.6 Leaked at all vacuums 2.2 2.4 2.0 1.9 5.3 3.7 2.4 2.8 Leaked at all vacuums Wo. 5 Flutter valve after 1 day in life oven ? Approximately the same as above. It was found that the flutter valves leaked greatly that at all vacuums without glycerine, but/with glycerine the leakage was greatly reduced. Likewise when the Goodrich- Lakeside valves were moistened with glycerine, the leak, either "Extend" or "Compressed", was reduced to zero. - 77 - Table 3 Val ves tested with glycerine Valve Setting 6" 4" OH T IT '~f X No. 5 Flutter A. T. Fitting Kops A. T. Fitting 1.1 1.3 .4 Goodr ich-Lakes thin wall ide 7/8" Normal Compressed .0.5 Compressed .10 Extended .05 jSx tended .10 Leaded at all vacuums Secular Leaked too much at to ^ret reading. all vacuums 10/82/18 Table 4 Dirtied valves Valves rubbed in sandy mud and water, thoroughly dried and cleaned as much as possible by violent blowing and beating. Valve Setting 6" 4" 2" 1" Goodrich -Lakeside 7/8" thin wall No. 5 Flutter Regular Normal 30.9 38.7 420 Over 400 A. T„ Fitting Leaks too much to get reading. T able 5 Salivated valves Same val ves, as above, washed thoroughly in clean water, dried, and well moistened with saliva. Goodrich-Lakeside 7/8" Normal thin wall No. 5 Flutter a. T. Fitting Regular .0 2. 1.5 30c9 22.3 27.7 73. 67,5 56. .4 14,9 19.8 - 78 - Conclusion s Small variations in degrees of compression are not important in the Goodrich-Lakeside valve. - The absence of glycerine on the valve is less fatal on a Goodrich -Lakeside than on a flutter valve. Six months' aging does not reduce the effieiency of the Goodrich-Lakeside val'/e. When they are dirtied, the Goodrich-Lakeside valve leaks less than the flutter. When they are moistened with saliva, the Goodrich- Lakeside leaks less than the flutter. - 79 - EXHIBIT X 3ub .1 eo t : Determine tion of range of vision of various masks. Object : To compare the visual fields of the differ en masks and show percentage of vision lost in wearing differed masks . Method of procedure : By means of a made perimeter, the subject, with head position fixed, looks at farthest point in a given angle. With eye on this point, the entire field of vision of the eye is determined by approaching this point from all directions with an object until the object is seen. Observations : See appended charts. Limitations of range of vision with masks is strikingly shown not only in the range of vision for each eye but also in the binocular field, or the field which is common to both eyes. These limitations in the binocular field are important, as they affect the subject's perception of space and distance (Plates Till, IX, X, XI). Conclusions : It is clear from the appended chart and table that the Pearce-Geer mask has after the normal the greatest percentage range of vision. It is also noted that the K.T. mask and the A.T. mask have practically the same rangre of vision. - 80 - * *» 1 ;; -j «Q - "--■ ^> -'.. 1 <3" c £ "*K '-I 'c ! o al 1— 1 ■-» t» 1 — 1 «\ > ■■ S a r <0 < v~l ~* Ai c c I- 4 a © ti ky, / / sr « 5 •N.y h JA ; "T^T" 35 ! : >. \ f i 3 X ^ 1 N ^ ! 1 £ : § i X. 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CD CD (3 CD CD CO H CD CD tS iTj ro at? cr 1 cd H- 4 Hj O B CD & P O H P- N O P 0*3 a* ; ' HCD P CD c+ y CD O H Hj O CO O CD p c+B B p" t^ CD CD HOB Hjp B B B CQ O CD P !*■ H H H CO B • P e? c+ H>p B- • c+ P CO P H-B B ■tq o o 1 P ej. a t-oa CD c+ P H O O P CD B I OB CD O CD l-i P B H p M CO «ci CD 0: CD CD B CD CD CD O O B P* H - I- 1 O B' B CH3 B P C+ B P CT" H CD CO CD H o Hj P CD 73 H CD CD CQ c+ § J Hj H" H CQ c+ CD O c*- B B- CD 0*3 H- CD < ■*-i H- B Hj CD CD P O H- H- S § p- O H- Hj CO p B" CD H CD H- 1 O H- c+B H- CD C B o Hj Hj H hi 5 b b 0) 3 ft* I 5 X Procedure : When the apparatus is connected, it is necessary, first of all, to test for leaks in the system. To do this five cubic centimeters of air are forced into the pocket to which the manometer is connected, and a 500 gram weight is placed on the air pocket. The compression of the air will, of course, increase the reading of the manometer, and if the circuit is air-tight this new reading will remain constant. The mask is then properly adjusted by the subject, and the air pockets are inserted between the band of the mask and the face. J?ive cubic centimeters of air are forced into each successive pocket and the corresponding reading of the manometer recorded* By this method it is possible to determine the variation in pressure of the mask against different parts of the face. - 83 - SXHIBIT XII Subjec t: The effect of ad;uitc=t- masks upon blood - flow in the temporal artery. Object : To determine whether the ligatures of a mask adjusted with sufficient tightness to afford protection, affect the bloodflow in an artery. Method : The temporal, being the most accessible and suitable artery of its size, was chosen and an estimation made of the normal pulse as to character and volume. A mask was adjusted with the tightness necessary to protect, and observations on the temporal artery repeated. Observations : See appended tables. Conclusion : Pressure of mask adjusted to face with sufficient tightness to protect may shut off blood supply to head and scalp by compressing arteries. - 84 - EFFECT OF MaSZS OH TEMPORAL ASTER I ZOPS : August 15,1918 Size Name Small Neeld Fit Arceria'J. flow OK n if McLeod Saul OK OK -1- Large Small it Large Small Hart Morrow Tucker Pearce Morgan York Hull OK OK OK OK OK OK OK -t- -»- -1- -1- -l- -»- -i- AKRON-TISSOT: Medium Neeld OK -\- Large MeLeod Saul Hart OK OK OK -1- 9 tt Morrow OK 9 Med ium if Tucker Pearce Morgan OK OK OK 9 -»- 9 it York Hull OK OK 9 GEEE MASK: Neeld OK - Saul OK - McLeod Hart Morrow OK OK OK 9 Tucker OK 9 Pearce Morgan York Hull OK OK OK OK - Remarks - 85 - Strap very tight; vessel obliterated by strap. Quite dif5tinct. Pulse felt when band was raised; lost when band was let fail. Good pulse; vessel under bam. Plain. More distinct than usual. Quite distinct. Faint. Plainer than usual. Pulse partly obliterated; vessel beneath strap. Quite distinct. Quite distinct. Wo pulse found; vessel below strap congested. No pulse found; no congestion below, No pulse found. Quite plain. Band too high for pulse; congestion below. Congested below Dands; post branch very faint. Faint; artery almost obliterated. When band is raised, pulse felt; drop band and pulse dies away. Faint. Faint. No pulse above; congestion below, Congestion below; no pulse felt. Not so plain, but clear. Quite distinct. Very plain. Quite plain. DESCRIPTION OF TEE LaKESIDE-GOODIUCH MaCHOE FOR DETERMINING THE GAS -TIGHTNESS OF A MASPZ, IRRESP3CTIVE OF THE F^iCE SEaL. The purpose of this machine is to determine the leakage in the masks that may he caused by faulty material or through careless manufacture. Leaks through the sides of the mask are obviated by means of a pneumatic band. This apparatus (Plate XIII) consists of a plaster of paris casting, so designed that it possesses the general contour of the human head and face. The casting acts as a model for the mask. At the sides of this casting a pneu- matic band is adjusted, which makes the air-tight joint between the sides of the mask and the model. At the air inlet (see diagram) a hand -pump is connected and sufficient air is forced in to inflate the pneumatic band. This band molds itself to the shave of the model and mask, making an air-tieht seal. The air inlet is then shut off by a screw clamp. The mask is also fitted with a pneumatic cork which connects it with the Pearce-York apparatus. The pneumatic cork consists of two concentric tubes, sealed at the ends, except for an opening through which air may be forced into the rubber jacket, thus making the joint air-tight. By means of the Pearce-York apparatus, sufficient air is then exhausted from the mask to give a vacuum of four - 86 - b a in ■■* A rr, t- 3 a. in IS in 3 inches of water. This vacuum will remain constant, ■provided all joints are air-tight. Since the face seal of the mask and other connections of the apparatus are sealed, any. decrease in the vacuum must be caused by leaks around the eye pieces or through the material itself * - 87 - EXHIBIT XIV THE HULL METHOD FOR PET^ltMIMflG THE MAXIMUM TdHSIOM .GjjIETiSD Bjf iHE HARUESS OF A MASK. The method consists in locating two points spaced just one inch apart on the different straps constituting the harness, and noting their elongation v*hen the mask is properly fitted on the subject. The mask is then removed and the force required to cause this elongation is measured. This is done by clamping the straps at original marks. Eye bolts are attached to the clamps. One of the eye bolts is then fixed, while an accurate spring balance is attached to the other one, and force is applied in a horizontal plane until the harness is stretched to the same extent as when adjusted to the subject. When this force is determined, the entire apparatus should rest on a table in order to obviate the error which would be caused by the weight of the mask itself. These results, when expressed in proper units, Five a relative comparison of the maximum tensions on the harness of the mask. An attempt was made to locate the two points in the same relative position with different masks in order to deduce a comparable interpretation of our results. - 88 - FORCES 3£dRT;SD M HSaD HjiRMjSSS. The attached photograph will show the latest design of «?as mask submitted by the Gas Defense Division, October 11, 1918, The arrangement of the head harness that is shown very closely approximates that now used on the K.T. and A. T. types of mask. It is this design that, in our minds, is entirely wrong. By resolving the mill of elastic Uo. 1, as shown in photograph, into its component forces at the point where it is attached to the mask, we have found that approximately 25% of the force is exerted alone the edge of the mask extend- ing upward. Seventy five per cent of this force is exerted along a line perpendicular to the edge of the mask extending to the back of the head. Elastic Wo. 2, when resolved into its component forces, results in about 45% of the force acting upward along the edge of the masit, and 55% acting in a line perpendicular to the edge of the masK and toward the back of the head. By resolving the pull on elastic No. 3, we find that aoTxroyimately 60% of the force is used in pulling the mask upward on the face, while 40% is acting directly against the forehead in a line perpendicular to a plane which is tangent to the head at this point of contact. We find that the frontal bones of different men vary greatly in shape, and it becomes very difficult to perfect - 99 - a gas-tight seal between the mask and this portion of the heaa by the method employed. On some subjects this latter force will act in such a direction as to/give a slight tensio* on the forehead binding, and consequently aid in making a gas-tight seal. On other men this force will act in such a direction as to give a slight pull on the forehead band toward the center of the forehead, thereby causing an open- ing, or a tendency in this direction, across the front of the forehead. There are still other men upon whom this force wil" not cause a pull in either direction along the band across the forehead. As was pointed out in the main discussion, gas-tight- ness could easily be obtained providing the head was a true sphere, and if such were the case red lines A and B (see photograph) would represent those lines along which tension should be applied in order to obtain gas -tightness with the least pressure on the head. By placing a semi-pneumatic pad over the temples and then taking a section through the head along the planes, we find that the line of contact of the face and mask is a continuous curve in one direction only. It is very easy to obtain a gas-tight contact between the face and the mask under this condition, as a slight tension of the harness at the back of the head will give a perfect seal. The same is true with a section taken along the plane fb), and gas-tightness can be obtained with equal accuracy when a small amount of tension is applied to the top of the head. - 90 - Since the method as described above will give gas- tightness, it is then only necessary to hold the mask in position or support it, which can be accomplished by one band connected to the center of the mask at the top and • extending directly over the head. These are in brief the principles which we have attempted to adhere to as closely as possible, and our reasons for so doing in designing the Lakeside-Goodrich mask. For data, see Exhibit XXI. 91-- EXHIBIT XVI RELATIONSHIP OP MASK L3AIQiG.cJ3 DETERMINED BY THE PE-dRCE- YORK METHOD TO THOSE DE?.SMIiiED BY TEE G*S CHAMBER TESTS. Purpose: To determine the amount of leak- in of a mask under a given reduced pressure which will give lachry- mation to the wearer when placed in chlorpicrin with a con- centration of 1030 p. p.m. Procedure : The subjects were fitted with X.T. masks, and adjustments were made in order to obtain gas- tightness, the only difference from fiehting conditions beine that the men wore nose clips. The canister was then attached to the Pearce-York apparatus (see Exhibit XVIII) and the leai-in determined under a certain reduced pressure. Observations: K.T. Masks A. T. Masks Subject Reduced Leakage Time pressure in c.c. in in. of per min. gas water Reduced Leakage Time pressure in c.c. in in. of per min. gas water 1. Wiley 3 1200 15' 4 380 4 f 2.Xheeter 2.5 600 15' 4 875 1' 3.Simonson 3 600 IE 1 4 228 10' 4.Strahler 4 600 15" 4 600 2" 5. Harris 3 520 15' 4 400 15" 6. Maize 2.5 1200 £' (too large to meas. ) 6" 7.Milner 3 500 4 248 15" 8. Simon 3 600 If 4 1200 2" 9.Conroy 2.5 360 3' 4 80 15" 10. Dinkey 2.5 856 t T 4 240 15" 11 .Storm 2.5 750 15' 4 240 15" 12. Hart 2.5 300 6' 4 150 15" The subjects were then placed in the gas chamber in a concentration of 1000 p. p.m. chlort>icrin without removing - 92 - masks or any further adjustment of the harness. If the men remained in the chamber 15 minutes without being lachrymated, the fit of the mask was considered satisfactory. The same men were tested in a like manner with A«T« masks. The results are tabulated below: Observations : With K.T. masks - 9 men (75%) were not lachrymated. - 3 men (25%) were lachrymated. With A.T. masks - 6 men (50%) were not lachrymated. - 6 men (50%) were lachrymated. Conclusions : Since the A.T. mask showed the lower quantitative leakage when tested with the Pearce-York appar- atus, but the larger percentage of lachrymations in the gas house , and the K. T. mask showed a greater degree of lea^apre by the Pearce-York method, but the smaller number of lach- rymations, there must be some other factor that actual leakage * that, plays a part in lachrymation of men wearing gas masks. Recommendation : That investigations be instituted to determine this factor. - 93 - EXHIBIT XVII PaRT I SUBJECT: The absorption of chlorpicrin and phosgene by A»T. and K. T. face pieces as determined physiologically. OBJECT; To show that any chlorpicrin and phosgene which leaks into a face piece through the rubber and skin seal is absorbed by the interior of the face piece. INTRODUCTION: During some experimental work at the B.F. Goodrich Rubber Company's plant st Aicron, Ohio, by members of the staff of the Lakeside Laboratory, it was noted that small amounts of chlorpicrin injected into the dead space of an a. T. or K. T. mas&: would disappear within a very short space of time. Later, a physiological method was developed by which small amounts of chlorpicrin could be determined with great rapidity and accuracy. Bv this method it was found possible to determine at short intervals of time the amount of unabsorbed gas in a mask while fitted to a subject. From these data, of e dorse, the rate of absorption of chlorpicrin by the face piece could be calculated. A similar method was not available for other gases, but qualitative tests showed that,, with phosgene at least, the rate of absorption was of the same order of magnitude as that of chlorpicrin. - 94 - APPARATUS AW METHOD: The apparatus for obtaining known concentrations of chlorpicrin was the same as that described in Part III of this report. Two methods were used in determining the rate of absorption. In the first method the A,T. and K.T. face pieces were provided with rubber breathing tubes and nose clips in a manner similar to the R.F,K. mask and fitted to subjects. The dead space of the masks was determined by water displacement, and known concentrations of chlorpicrin were introduced therein by means of a syringe. The needle of the syringe was forced through the fabric of the face piece. Ordinarily, in maiting a test the subject opens his eyes at intervals of one minute, However, when the mask was rendered more non-absorbent by means of various coatings, such as water, gelatine, etc., the time had to be extended from 2 to 5 minutes. It was found impracticable for a sub- ject to perform more than four determinations in any one test without a rest, The concentration of chlorpicrin usually ■put into the masfc, was 30 p. pan. This is approximately the highest limit of accuracy for the physiological test. To make certain that the injected gas was thoroughly mixed with the air in the mask, the subject was required to shake his head vigorously immediately after the introduction of the gas. - 95 - h.T.MoLsk. ~Ruhber 6Topper PLATE XIV 7WS?3c[> Empty Bottle. Cfjcmicai Warfare uerv/ce U.S.A. Medical Division. Phys/o logical Laboratory Lakeside Hospital - ClevoI<*.nd O. Apparatus Tor Testing Ihcepiecedfbr Absorption of G ZS~G<5£. In some cases where the absorption rate of the face piece was comparatively slow, the apparatus shown in Plate XIV was made use of. This consists sim-ply in attaching the mask to the side of a suitable empty bottle. The mask practically a perfect seal over the shoulder of the bottle. By this method the manipulation was essentially the same, except that determinations were made by applying the eye to the inhalation tube of the die-casting. The qualitative tests with phosgene were performed with this method. It was found that 50 -p,p.m» introduced into an A.T. mask could barely be detected in 5 minutes. and had entirely disappeared in 10 minutes. DATA: Table I ABSORPTION OF CHLORPICBIfi BY K*T. PACSPISC3S Time in Mask Mask Mask Mask Mask Mask mask dry dry dry wet wet wet Gone, Cone. Gone. Cone. Cone. Cone. p. n.m. p. p.m. p. p.m. p.x>.m. p. p.m. p . p . m . At start 30 30 30 30 15 30 1 min. 16 13 18 --• 7.5 __ 2 min. 7 -- -- 15 3.0 -- 3 min. 4 4.5 4 13 2.0 10 4 min. 2 2*5 2 11 -- 5 min. -- -- _. 7 -- 5 - 96 - TABL3 II ABSORPTION OF CHLQRPIC2IM Bi A.I. FACE BldCdS Time in Mask Mask Mask Mask Time in- Mass gelati mask dry dry wet wet mask coated Cone. Cone. Cone. Cone. Cone. to. p.m. p. p.m. p. p.m. p.p.m * p. p.m. At start 30 30 30 30 At start 30 1 min. 7 7 20 20 S min. 23.5 2 min. 4 4 16 12 4. min. 17.0 3 min. — 1.5 7.5 Less than 7 min. 5 7.5 4 min. — -- 5 -- 10 min. 6.5 5 min. — — 3 -- 15 min. 5.0 Discussion of results: From these experiments it is apparent that the absorption of ehlorpicrin and phosgene by the face pieces of Tissot masks is sufficient to account for the fact that men wearing them are not gassed even when the leak- in per minute is dangerously high. The leak-in in both the A.T. and the X.T. masks must take place through fine capillaries between the mask edpre an^ the face. The conditions are thus almost ideal for absorpti^ CONCLUSIONS:- (1) Both K.T. and A', T. masks absorb chloi- picrin and phosgene at such a rate that concentrations of 40 p.p.m. of each gas practically disappear in 5 minutes. (2) This absorption is sufficient to account for the failure of many leaky masks to gas the wearer when the leaicasre takes place at the seal between the mask and the face. - 97 - PART II SUBJECT: The absorption of chlorpicrin by rubber face pieoe material. OBJECT: To supplement work of Part I. INTRODUCTION: In order to obviate any doubts that mieht arise as to the experimental methods used in Part I of this - report, it was decided to repeat some of the work in such a manner that variables, such as diffusion of the gas through leass, absorption by the face, etc., would be eliminated. The following experimental work in which these vari- ables were eliminated or controlled, was, therefore, under- taken : APPARATUS AND M3TEGD: The apparatus for this work consisted of a lamp bulb such as is described in Part III for use in eye calibrations. This bulb was fitted with a heavily paraffined rubber stoprer, through which a capillary tube was inserted* The bore of this tube was slightly larger in diameter than the needle of the syringe used to put in the known amounts of chlorpicrin. The samples used consisted of -carts of A. T. face pieces, from which the cloth outer covering was stripped and a piece of 1/16 inch thick hose. In the first series of experiments pieces of rubber of known area were placed in the bulb. Definite quantities of chlorpicrin, usually 50 p. p.m. , were introduced and the unabsorbed gas determined at intervals by the physiological - 98 - method described in Part ill. n this series comparatively larsre samples of rubber were use I and the time of absorption was consequently short. In the second series of tests the quantity of rubber was varied between the limits of 1/8 sq. in. and 8 sq.in. The amount of unabsorbed gas was determined at the expiration of 18 hours. Data and curves on the experiments follow, (Plate XV and XVI). The determinations were made by Lakeside Physiological Method. TABLil I THii aBSOHPTIOH OF GLLOHPTCEM BY HUBB3B Vol. of Bulb - 785 c.c. 19 sq.in. Same sampi e 32 sq. in. Same sam- 144 sq'eir: at face repeated at. face pie re- 1/16" rub piece piece peated ber hose stock Time of C one. c one. Cone. Cone. C one. exposure P .p.m. p .p.m. p .p.m. p. p.m. p .p.m. At start 50 50 50 50 50 1 min. — 30 10.5 13 4.5 £ min. -- 20 6.5 7 1.0 3 min. 16 15 3.5 Less than 5 -- 5 min. 13 13 3.0 -- -- 10 min. r.E 10 2.5 -- -- - 99 - C-aJ UnalnorU f / t 7 V / 1 j / I _ I r / / 3 t 1 c / / f > 1 f 1 1 1 1 I ■ & 1 1 1 1 1 1 ! 1 1 ^ ^ £' s- s- jfcj. Vrf — * K — i 1 ^ ai r O o r? 0) ft e ^ ^ f ffc- rg ' 1 I I i : i — i i 1 % o 3 c D c Qi PL ft c M Q> N Thrfo per Million Gi 2.S Ufiah-jorberi M* On •■}: O f\i -|\ c- Oi d. N) .^ •*h "~f i ™jLr ig-MI ~ I i _i_._ ... . . . l_j ' '■■ *"" @ N"h i / ! , "j . | . i i j i 1 1 r i i ; ! - 4- 1 N Q ' , i N <* 10 t* *, ^ CN I * OK i „.. CN o> ft N 85 i£ i i — i i j 1 °1 v 1 (3s s """"^T"™ % 1 - a r L —- i 1 ! , D ^ " — — h ( -J— ,. 1 TABL iil j. I CHLORPICEIN ABSORBED B5T VARYING AMOUNTS OF A.T. FiiC3-PI3CiC MATERIAL Volume of Bulb 500 c.c. Initial Concentration SO p. p.m. Size of Rubber P.T).m. Unabsorbed sq. in. at end of 18 hrs. 1/4 11. 1/2 5,0 1 4.0 2 3.5 4 2.0 8 1.0 DISCUSSION OF RESULTS: This work is a very helpful confirmation of that of Part I. It shows that, other thing's being- equal, the absorption of a given amount of chlorpicrin by rubber increases both in ratii&ity and completeness with the increased surface exposed. Obviously with the large surface of the face piece of the mask and the small lateral distance the gas molecules have to travel to come in contact with the rubber while leaking into the mask, the absorption will be rapid and complete. CONCLUSION: The absorption of a eriven quantity of chlorpicrin by rubber increases both in rapidity and complete ness with the amount of surface exposed. - 100 - PART III SU3J3CT: A physiological method for the estimation of small quantities of chlorpicrin. INTRODUCTION: It has often been noted that small concentrations of chlorpicrin in air affect the eye in such a manner that its closing is practically involuntary. It was also noted that a measurable time elapses between the instant of exposure to the gas and the time when the eye closes involumtarily. The following is a description of the method by which these facts were utilized in determining, with a very close decree of approximation, concentrations of chlorpicrin in air ranging from 1 to 25 p«p.ra* Below 1 or 2 p.tj.m. the average eye withstands the gas without being permanently closed, though considerable blinking may be caused. Above 25 p. p.m. , the reaction of the eye is so rapid as to render proper timing out of the question. Highe-. concentrations may of course be determined by diluting them to fall within the above mentioned range* APPARATUS: Before determinations of chlorpicrin con- centrations can be made, the eyes of the operators must be calibrated by exposure to known amounts of chlorpicrin di- luted with varying known quantities of air. The arrangement of apparatus necessary for this cali- bration is shown in Plate XVII. - 101- i rj"n»ijlniyiTi"ijTj The apparatus consists of the following: A. Sulphuric acid drying-bottle for drying air. B. Trap to prevent blowing over of acid or sucking back of chlorpicrin. C. Ice bath to hold chlorpicrin at constant tempera- tures. D. Rubber bottle to enable air to be blown through ehlornicrin. E. Ground-glass syringe, 2 cc. capacity, graduated in tenths of a cc. (syringe should be lubricated with glycerin , in which chlorpicrin is quite insoluble). F. Glass bulb with short neck the end of which will fit into the eye like an eye-cup. This bulb can be of any convenient capacity, and should be fitted with a heavily paraffined rubber stopper, through which a piece of capil- lary tubing should be inserted. The bore of the capillary should be a trifle larger than the syringe needle, ( The bulb usee! in our work had a capacity of 785 cc This was Very convenient, as experience has shewn that the concen- tration of the gas from the bubbler averages 7 ,.85 parts per thousand. Thus 1 cc of gas from the bubbler diluted with air in the bulb s 10 iD.p.m. concentration). G. Stop-watch for recording time of the eye reaction. METHOD: The apparatus having been assembled, a sample ranering from .1 cc. to 2 cc, is withdrawn from the bubbler with the syringe and introduced into the bulb through the capillary. The bulb is then shaken a few times to mix the gas, the stopper is quickly removed, and the neck of the bulb placed over the closed eye of the subject. He then opens his eye normally, at the same time starting the stop- watch. Within from 3 to 30 seconds, depending of course upon the concentration of gas, the subject will have an overpowering impulse to close his eye, At this point the - 102 - stop-watch is stopped and the time recorded. A series of tests should be run, varying the concentration up to the limit of endurance of the subject. Convenient concentrations to test are 2.5, 5, 7.5, 10., 15, 20 and 25 p„p.m. From the data thus obtained, a calibration curve can be drawn plotting the concentration in p. p.m. against the time to eye reactior in seconds. Samples of such curves are shown in Plate XVIII. Having calibrated the eye of the subject, one can determine the concentration of chlorpicrin in any vessel or room by simply recording the time to the eye reaction and reading the concentration by reference to the calibration curve. SUMMAR/ 1. A physiological method for the determination of small concentrations of ofclorpicrin in air has been developed. This method has a ranere of from 1 to 25 p. p.m. , and is proba- bly accurate to at least 2 T>.p.m. in the higher part of the range . 2. The method developed should be useful in the labor- atory wherever small quantities of chlorpicrin have to be determined. There is a possibility that it may also find utilitv in the field. 3. It is proposed to try out this method for other gases that affect the eye in a manner similar to chlorpicrin. - 103 - mm CO/VC£~A/T&A7-/OA/ OF Q-ZS- /n /?>?Af. 3¥E SEHSITIVIT* CALIBRATIONS AGaIHST CHLQRPICEIH Cone, Rector Reimann Proser Whittlesey p. p.m. Sees. Sees. Sees. Sees. 20.0 4.0 — 5.0 5.0 15.0 5.4 — 5.4 6.0 io.o 7.5 2.5 7.5 7.5 7.5 9.0 4.4 10.0 17.0 5.0 13.0 9.0 15.0 40.0 2*5 18.0 12.0 30.0 — *■ part iv StJBJSCT: A comparison of the absorption of ehlorpicri?: and phosgene by rubber as determined chemically. 03JSCT: To determine if the rate of absorption by rubber of phosgene is as rapid as that of chlorpicrin. APPARATUS: The assembly of apparatus used in these experiments is shown in Plate XIX. The essential parts of the apparatus are: (1) A tubulated glass bulb of 1000 c.c. capacity used as the absorption chamber. (2) A Geissler potash bulb used for absorbing that portion of the gas not held by the rubber- (3) A ten-liter aspirator bottle for drawing the gases through the absorbing solutions. (4) A glass rod in the absorption chamber from which the sample of rubber is suspended. METHOD: The sample selected (in this case all samples were taken from a sheet of rubber used in making the M.Z.T. masks } was cut into a strip 1 inch wide and 8 inches long. - 104 - This strip was suspended longitudinally in the absorption bulb. A known amount of gas was then introduced into the bulb and allowed to remain ior varying lengths of time, The time of exposure ranged from fifteen minutes to sixteen hours. At the expiration of the selected time, the remaining gas was drawn through the absorption bulb and the amount determined chemically. In the case of phosgene the ffas was put into the bulb by means of a syringe graduated in hundredths of a cubic centimeter, The unabsorbed gas was determined by absorption in decinormal alcoholic soda solution and titration with N/150 silver nitrate solution after neutralizing the alcoholic soda with dilute nitric acid. With chloipicrin the same apparatus was used as that described in "A Physiological Method for the Determination of Ghlorpicrin." The gas was run into the bulb by means of a short Hempel Burette filled with mercury. The unabsorbed chlorpicrin was determined by absorption in a half saturated solution of sodium sulphate in 50% alsohol and determination of chlorides was made by the Volhard method. - 105 - Size of Test Piece - I" x 8" Volume of Bulb - 1000 c.c. Chloroicrin Phosgene Time unabsorbed % unabsorbed Pop»m» unabsorbed unabsorbed At start 650 100 900 100 15 rain. 440 78 30 min, 320 49 640 71 1 hr. 270 42 440 49 2 hrs. 200 31 4 hrs* 230 25 6 hrs* 180 28 16 hrs. 160 25 None by analysis 0-h DISCUSSION OF RESULTS; It will be noted that the absorption curves (Plate XX) cross at three hours' exposure. This indicates that the chlorpicrin is absorbed at a faster rate than phosgene, but is also given up at a faster rate when fresh air is drawn into the bulb. The effects of these Phenomena are accentuated by the fact that tan liters of fresh air are drawn over the sample during the course of the analysis When the chlorpicrin charged test piece is dropped int«- a 500 c.c. bottle of fresh air, within the space of five min- utes the air in the bottle will cause the eye to close in less than four seconds, indicating that the chlorpicrin is given up quite rapidly When the equilibrium is disturbed. - 106 - k ^ £ 3 q: ^ o Mi o ^O c V5 G '■6 ■V < *K 5 o ^O 'p-90JO9ODUn £#r) jo JW2JJ9J The same, is true, however, of phosgene and it is probable that there is a chemical combination between the rubber and the s?as, With chlorpicrin the phenomena are apparently those of solution. CONCLUSIONS; (1) Rubber absorbs phosgene at approximately the same rate as chlorpicrin. (2) Although the absorption of phosgene is not (juite as fast as that of chlorpicrin, the gas is held more firmly and is not ?iven when exposed to fresh air as in the case of chlorpicrin. - 107 - EXHIBIT XVIII DESCRIPTION OP THE PEARCE-YORK APPARATUS FOR TESTING LEAKAGE OF GAS MASKS Purpose of the apparatus : To give a quantitative measure of the leakage of the mask under all conditions. Apparatus : This consists of a brass pipe (Plats XXI) on one end of which is soldered a 3/4" three-way stopcock, and on the other end a tambour. There are three straight waycocks soldered along this pipe; one being connected to a Luer ground glass syringe (100 c.c. capacity), the second opening into the air, and the third connecting with a grease gun of about 500 e.c. capacity. Procedure*. After the mask is properly fitted to the subject, the canister is removed from the knapsack and the check valve taken out. The rubber stoprer is forced into the bottom of the canister in order to make it gas-tight. The subject is allowed to breathe normally through the three-way stopcock (a). At the signal he will close his lips tightly and hold his breath. The three-way stopcock is turned to give a direct passage from the canister to the tambour. The piston of the grease f?un is then Trailed until the desired redueed pressure is registered on the tambour, and then the stopcock (b) is closed. Time is taken at this pointy and the desired reduoed pressure is maintained by pull- ing out the piston of the Luer syringe. At the end of 15 seconds, the stopcock (a) is turned to allow the subject to - 108 * u >\'VVV © I S ^ l® 11 1L s G , I L . 51 > > B ^4 is i ■ i ■ i* i- 1- i-i-i-i*! 9 » ©o o © e> «> e> o o 1 - 1 o iv a ■st U 3 5t> *** * ^ Co S> •3 •rti t T~ Ufo 5 < to 5t> r i £ < * r © i -o > M 3= T breathe again normally, and the volume of air which has leaked in is read at the reduced pressure in the glass syringe* Stopcocks B and G are then opened, and the air is expelled from the Luer syringe and the grease guns* Stop- cock C is then closed and the apparatus is ready for another test* - 109 - EXHIBIT XH COMPARISON OF HEiiD MEASUREMENTS Object: To determine the most uniform measurements of the head with reference to mask adjustment. Method : Careful measurements were made of 175 heads in the diameter and the circumference indicated by appended face diagram fPlate XXII), Observations : Figures in upper line express measure- ment in inches of the diameter designated by figures referring to face diagram. The second row of figures denotes in per- centage the frequencyof the designated diameter;- e.g.,- 29.9 per cent of cases have a Ko.l diameter of 2§ inches. Table MEASUREMENTS OF HEaD PER ATTACHED DliiGR^M Based on 175 eases No* 1 Diameter: Inches - 2f % - 29.9 3 53 17 3i 6.5 3f 4 No. 2 Diameter: 1.6 5 29.6 5,6 H 5f No.. 3 Diameter: 1.6 4* 9 16.6 6 43.5 5i 17 5t 13 Mo. 4 Circumference: 20^ 1>6 20f .-3 20f .8 21 3,3 2li 3.3 5.8 21f 5.8 22 20.5 22f 10.7 22-§- 20.5 - 110 22f 8., 23 19 23f- 2.5 23|- 4- DlAG&AMMATiC §NMX OF H£AD M£ASUZ£M£NTS PT.ATE XXII Was. / ? ZffJ are /'was- eftsfatceG Nos. --■'£ Wirm*rA\ViimnBltq PLATE XXI II PRESSURE POINTS FACE DIA6RAM. I I A/) Others ojssswm- iA. , 3fc?ni!."in* J aSHB«iiB;if^2Sf as* >■*!•-. w.^ i*'' '.I^tJ^L(?W»3«SBM££Kra»»nMnHMKtt« Jp/SESSUEES-i'* """»• /ww/y *8* 2 *S T < a ^0 H P> M X <1 f a ft \ .3 rn 0) 5 0i ft > 1 . - S$l/%£S - in mm. met-evty It- > HI K X * ■ v ^ ■ I* ft I EXHIBIT XXI Subject : The effect that a rearrangement of the harness has upon the leakage in the mask and the tensions in the harness. Object : To locate positions for the harness whereby the efficiency of protection would be increased to a maximum. Discussion and procedure : The leakage and the tensiom in the harness were determined in a number of different types of mask. The harness was then removed and the general direc- tion of the strap altered (see Exhibit XV). The straps are designated numerically, starting- with the lowest one on the right (facing the back of the mask) and continuing counter-clockwise. This gives a total of six straps in the harness. These straps were then removed, and the gen- eral directions of straps 2 and 3 interchanged. The/top strap (3) was now nulled in a horizontal plane around the back of the head, where it was fastened to former strap 4 now running in the same general direction. These two straps are combined into one, which is designated as strap 3. Former strap/is next shifted 90° (clockwise) so that it runs up on top of the head. Here it is buckled to former strap 5, which is now also running up. Straps 2 and 5 are now Known as 2. Former straps 1 and 6 are fastened back of the neck. These are com- bined into one strap, which is now called strap 1. The results obtained in these experiments are given immediately below. - 114 - Table Type of mask Leakage c . c . t>er rain. Length of strap Tension in pour&s Mask A: Large. Could (1) 6,50 1 -, 40 K. T. Oct. 5, 1918 not be (2) So 75 1,60 Old strap. determined. (5) (4) <5) (6) 5,00 4,50 5,25 6*50 2,20 2»2C 1.75 1,00 Same with 500 c.c. (1) 12,50 2,00 new straps 2" suction (2) (3) 15,00 10.00 1 3 50 5,00 Mask Bt 120 c.c. (1) 5,50 X ■y k*D K, T.M. Oct. 11, : 1918 4" suction (z) 4,25 2.25 Latest New York type. (5) 5n00 2,50 No band seal. (4) 5,00 2,25 (5) 4,75 1.50 (6) 5,50 l.,25 Same with 104 c.c. (1) 11.00 1.25 new straps 4" suction (2) (3) 12-50 10 c 50 1,75 2,00 Mask C : 275 c.c. il) 4,00 1.75 K.T.M. Oct, .11, 1918 4" suction {2) 5.00 2,00 Latest New York type. (3) 4.75 1.50 With cloth band seal. (4) (5) (6) 4.75 5.50 5.50 1.75 1.50 1.75 Same with 275. c.c. (1) 9.75 1.50 new straps 4" suction (2) 12.00 2.50 (3) Latest Lakeside- Goodrich 10/2/18 40 c.c. 4" suction No straps Mask I : A.T, Production Oct. 5 1918 72 c.c, 4'' suction Subject: Carey. - 115 - Conclusion s : By interchanging the directions of pull of strata 2 and 3 on the rieht of the mask flookjng at the back of the mask) and straps 4 and (3 on the left of the mask, a small reduction in the leakage was obtained, especially so in the K.T. mask. This change in straps, however, caused a slight gap near the temples with the K.T- mask, which could be remedied by padding these ends. With the K.T. II. mask (cloth band seal), there was no apparent improvement obtained by altering the directions of the straps (Plate XXVIT). - 116 - iftOS J EXHIBIT aZI I Subject : Determination of the leak-in of A.T. and Z.T. masics under exercise in chlorpiCiin concentrations of 1-1000. Object : To find an explanation of the facts that A. T. and K.T» masks leak and yet subjects complained of gas. Later, when canisters with a resistance of 2 inches at 85 liters were connected to the inspiratory tubes of the mask, the same results were obtainef- that is, nous was gassed, providing the mask was well fitted and was satisfactory in the gas house during test. This in spite of the leak that was demonstrated with the Pearce-York apparatus previous to the entrance of the subject into the ffas house, and in spite of the fact that the leak demonstratec. was of such a size as to allow sufficient gas-laden air to enter the mask to thoroughly gas a man with each inspiration. Table 1 Mean neg. % Time Leak-in P. p.m. gas in pressure neg. per min. mask. Chamber Subject Mask inches HgO Pres. c.c, cone. 1-1000 '.7.F.L. KT3A10 1.75 59.4 332 8.1 7/.F.L. KT3A10 1.1 46.0 161 3.9 T.L.W. ET3.a5 2.0 64.4 283 6.2 O.S.L. KT2Q9 2.2 53.8 425 10.3 J.-^.C. KT4a7 1.8 60.7 388 9.4 J.W,C. KT4A7 2.25 73.6 588 14.4 H . J • H • ZT3A6 2.0 61 . 4 492 12.3 H.J . H . AT301 1.2 42.0 67 1.6 The conclusion from these facts is forced to the effect that the gas which leaked into the mask with each inspiration was somehow rendered inert. The probability which was seized upon was that it was absorbed by the skin - 119 - of the rubber in the masks . (Ground up rubber had been demon- strated before to absorb chlorpierin). The lea& apparatus was then ta^en into the gas house, and tests were made to determine actually how much air which contained 1-1000 of chlorpierin could be suckedrinto the mask per minute without causing eye symptoms., The subject during these experiments breathed through an R.F.E., tube fitted into an ordinary A.T. or IC.T. mas]?, and had his nose clipped, A IC.T. mask fitted on Lieut. B-- allowed 10 c.c. of gas-laden air to leak in in 15 seconds under a -J inch pressure without gassing the subject. Under a §- inch pressure, 25 c.c. were drawn in in 15 minutes and Yery slight eye symptoms were ex- perienced. It was afterwards determined that 2 c.c. of the same e-as concentration were sufficient to thoroughly gas him when it was introduced quickly into the raas& with a syringe. Later experiments had the object of determining the maximum minute volume of air which could be drawn into a well- fitted mask at a steady rate without gassing the subject. The R.F.K. mouth piece was fitted into the masks exactly as in the first experiments. Subject Mask Carey A.T, w A.T, IT A.T. IT A.T. Lewald K.T. Minute Time of 1*3. CG C * C o gassing 20 2 minutes 40 \ minute 200 Immediate 10 JMot gassed in 5 min 20 2 J- minutes - 120 BSSULTS 1. Both A. I 1 . and K.T. masks when well fitted leaked on an aveia*?e of 20 c.c. and 75 o.c. respectively in 15 secor under a 1 inch suction pressure. This leak in an atmosphere of 1-1000 of chloroierin would be enouerh to thoroughly gas a man, 2» In spite of these leaks, all of the masks pro tea t aerainst chlorpicrin in concentrations averaging 1-1000 part3, both at rest and during exercise. 3. The chlorpicrin is evidently rendered inert if it leaks into the mask before it reaches the subject's eyes or his respiratory Dassae-es. 4, "hen gas-laden air is interruptedly sucked into a mask while the subject is breathing through an S.F.IC. tube, it takes a less quantity to gas the subject than if the gas- laden air were sucked in while the subject was breathing in and out through ordinary A.T, and K.T. connections. This latter fact is of course explained by the currents of air goir< in and out of the mask during inspiration and expiration, and by the fact that the respiratory passages are less sensitive in most individuals than the eyes, and therefore a small amount could be breathed in without causine respiratory symp- toms, whereas it would cause lachrymation. If the masks leak in, they also leak out; and therefore there must be at every expiration a certain amount of clearing of the mask. - 121 - ANALYSIS OF GaS FROM L&IK FOR ' fiLORPICRIJJ The sample of air from within the mask was drawn for analysis by means of a siphon bottle, and measured by running the water into a bottle calibrated from 1 to 18 liters. Tho air was drawn first through an electric furnace consisting of a | inch hard-glass tube wound with nichrbme ribbon wire. The temperature was controlled within 450~500°C. by means of a rheostat. Ohlorpicrin upon being heated to that temperature breaks up, and nearly all the chlorine is set free. At a con- centration Of more than 100 parts per million, complete de- conroosition is not assured, but no such concentrations were to be analyzed. The free chlorine was then drawn through a tube containing 50 c.c. Zh per cent KI solution into which had been nut a measured amount of .00614 normal sodium thio- sulphate. The iodine set free by the chlorine from the KI reacts with the thiosulphate. The thiosulphate remaining was titrated with .00614 normal iodine solution. One c.c. of .00614 thiosulphate equals 0.05 c.c. of chlorpierin at 25°C. and 760 mm. pressure (which approximates working conditions), from which data the parts per million in the sample analyzed could be calculated by.: C.c. thiosulphate used x .05 x 10 Volume of sample - 122 - exhibit xim Sub ject : Inha.la cicn resistance of gas masks. Object : To deter raise the resistance to inhala.i-.iov. tif various gas masks. Apparat us : The mask fits snugly onto a plaster of paris head (Plato XXVIII). A large motor-driven pump without valves imitates inspiration, the air being drawn through a -§•" tube running from the mouth of the dummy through the back of the head. A tambour, connected with the inhalation tube, gives pressure values, which are graphically recorded on a smoked drum. . Method : The canister is detached from the mask, and was the exhalation valve shut tight. Ho valve/inserted into inhalation tube* The pump is run at two speeds: 1. 22.5 r.p-m. - delivering 29.49 liters per rain* 2, 62.00 r.p.m* - delivering 82 liters per min. Two sets of curves, superimposed, are made: 1. With mask attached to dummy. 2. Of dummy alone. The difference between the curves gives the real value of inhalation resistance of the mask tested * NOTE* Since the action of the pump is reciprocal, the curve is partly above and partly belcw the line, The part below represents inhalation pressure; the part above is neglected. - 123 - The masks tested werer K.T, , regular type, #273X300, dated. 0ct*4, 1918 A.T., " " , dated Got, 12, 1918 Z-T.M* (with hood plate), reoent improvement, Long island Laboratory. Goodrich -Laice side, dated 3-16 e Goodrich-lakeside, dated 3-19. Table RESISTANCE TO INSPIRATION BY GOODRICH VaLV A- TESTING MACHINE 29.49 liters p ra. 82 liters p,m. jo com- % com= 6 :T stroke 6 ,: stroke pared pared 22i5 r.p.m, 63 rrp„m. with with Mask Dummy Dummy Mask Dummy Dummy Mask and and JCT. A,T. mask mask X.T.* ,1 .05 .05 2.1 1.1 1.0 100 18.8 A.T.# .7 .05 .65 6.5 1.2 5,3 530 100 K.T.M. .4 .05 .35 4.0 1 c 2 2.8 280 52.8 G.L.3-16 .35 .05 . 3 3.6 1.25 2.45 245 46.2 G.L.3-19 3.4 1.15 2.25 225 42.4 *8731300 Oct. 4 fr Oct. 12. A tracing made by co..:binin.t the curves by superimposing them 18 shown in Piste XXIX. Sources of Err or 1. Leaicaffe between mask and dummy. --This was certain- ly small. The dummy's face was smoothed, and the masks fitted t i eh tl y ■ 2. Rate of pump. - The pump was motor-driven. The current was constant, and the diameter of the pump so large - 124 - Curves showing inhaJa-tioft resistances, of various t^pes of wa*Ks. The significant part of the curve lie* Curve [Vo I Curve given by duwwy wriiheut; mask. Curve ti 2- (Exhale valvtf c|.os§s: la Halation tw&e open.. Curve gcye ^s in Ho Z) Cur** ftb t Cur^e tftveq fry the A ,T. M&ak (Vulfe 4n« a& (n ffc? 2.. Pump evas delivering 23-5 Liters of air per piinute ., tJhe. ThaxJtnuwi Ve]e>cz.tsf of %he &(. r ws MoU-t Ss'O Hirers per*- minute* PLATE /.XII that small variations in speed had little or no effect. 3. Calibration of tambour. - This was not all that could be desired. Comparative values are however quite re- liable. Conclusions The K.T* mask has -the lowest resistance of -the five at both low and high rates of inhalation, The A.T, mask has the highest resistance of the five at both low and high rates of inhalation- « The order of values between is as follows: Low Rate High Rate Lowest ... Z.T, lowest ... K*T. K.T.M, G.L, (3-19) G.I,. (3-16; G.L. (3-16) Highest ... A.T. iC-T.M. Highest ... A-Tc Summary The resistance to inspiration offered by the regular A.T. masks at high breathing rates is sufficient to seriously embarrass respiration, and should be remedied. The last model of mask submitted by the Long Island Laboratory, Gas Defense, is a distinct improvement in this respect. The Lakeside-Goodrich mask, although offering a higher resistance than the K,T* mask at lower rates of breathing, is better than the new mask submitted by the Gas Defense Sei^ice. - 125 - EXHIBIT XXIV A COMPARATIVE STUDY OP jIXHaJjATIOK YALV3S General introduction ; There are two general types of exhalation valve: fl) the flutter valve and (2) the Good- rich valve. The flutter valve is a flattened cylinder, fully open at one end, with the other sealed but with slits on opposite sides for the escape of air, fitted in a steel frame which acts as a guard. It has been made in three models; (l ) the standard model, used on the British and American masses; (2) a shorter, wider valve used on the Kops masks and without the fold at the end; and (3) a valve called the No. 5 model, made of thinner stock than the standard and without the fold in the rubber at the end. The Goodrich type of valve also known ^s the Geer valve is a two-part, circular one, protected by a substantial cage against external injury. The Goodrich valve has been made in a number of ways, all depending upon the same principle, and a study has been made of that model which ffives the best service. Sections of these models and details of all valves are shown in Plate XX X. Plate XXXI illustrates the fitting's. The data which were sought for in this study relate to (1) the resistance to opening. (2) resistance to continued air flow, (3) leaKa.ee, (4) durability, (5) the effect of cold, and (6} the effect of cure. Most of these data were obtained in the Goodrich laboratory under the direction of In C. Roller- - 126 - V"/* 7/8" x 1-3/4" HEAVY WALL 7/8" x 1-3/4" Thin Wall T7 3/4" GASK MASK VALVES PLATE XXX 44 SPHERRICAL HOLLOW STEM SPHERIVAL SOLID STEM > f 7/8" x 1-1/2" Thin Wall NO. 5 ENGLISH GAS MASK VALVE FITTINGS 5/8 inch PLATE XXXI The tests were made under varying conditions simulating but exaggerating those lively to be encountered in actual service. As many valves were tested as time permitted, but it is possi- ble that a slight revision of figures may be necessary when an analysis is made of tests covering a long period of time. Inasmuch as certain types of valve were found to be more desirable than others, the most intensive investigation was made of the Goodrich 7/8" type and Wo. 5 flutter, since preliminary investigations showed that these valves grave the best results. The rating of each type of valve on the basis of 100 per cent is given in the summary table. These figures are admittedly arbitrary in several respects, but as far as possibl the values assigned have been calculated from numerical data. 3ach object of study has been made the subject of a part of the report. - 127 - PaHT I Subject : Resistance of exhalation valves. Object : To determine resistance of exhalation valves under various conditions. See General Introduction* Discussion : The two important points in the matter of resistance are: (1) force required to unseal and (2) i'orce required to maintain the opening. The smaller these forces are, the less effort will be required for breathing. This study has been made in two ways: (1) directly on a man, and (2) by mechanical means whereby the conditions could be better controlled than in the man types, MAIJ T3ST In this experiment the resistance of four different reives were measured by two methods. First, the resistances were measured by allowing the subject to breathe through the valves. By means of proper connections a relationship was obtained among volume, resistance and time of the respiratory cycle. The pressure drop of each of these valves v*as then ascertained at a constant flow. Apparatus : A large tambour acted as the respiration chamber. The diagram described by the tambour on a moving smoked chart, when properly calibrated, erave an index to the amount of air inspired, a ruober hose connecting the side of the mask with a tambour, recorded -the pressure diagram. The time of the respiratory cycle was accurately measured by a - 128 - Jacquet chronometer, a three-ray stopcock connected the subject with the respiration chamber and the outside air. Pro cedu re: The subject first breathed room air through the side opening of the three-way valve. He then exhaled completely, at the termination of which he signalled to the operator , who connected the three-way waive with the respiration chamber. The pressure and volume diagram of the respiratory cycle was then described on the moving smo,ced drum. In this test the inspired air, not expired air, was measured, The reason for this was due to the nany technical difficulties that had to be surmounted in order to measure accurately the expired air with a flutter valve attached to the mask, however, under normal conditions the volume of the expired air is very nearly equal to the volume of the inspired air, making the error involved of little importance, From the volume and time curves the average rate per unit of time was calculated, while the pressure chart, when calibrated.. ?ave the drop corresponding- to the rate of flow. Results : At a flow of 68 liters per minute, the max- imum and minimum pressure drops of the neuy Goodrich valve werf- only 0.30" and 0.25" of v.ster respectively; while/flTe new flutter valve the corresponding drops were 1.40" and 0.6". Note the wide decrement between maximum and mean pressure drops with the new flutter valves. This probably indicates that a certain amount of adhesion tases place between the - 129 - sides of the valves, which., of course, is maximum at the beginning of expiration* Mote also that this does not occur with the latest Goodrich valve.. These results show that- from the standpoint of economy of protection, the Goodrich valve is by far superior to the latest designed flutter valve, However, final judgment must be suspended until a comparison of their efficiency of protection is ascertained* COMPARISON OF RESISTANCES 0.? DIFFERENT TYPES OF VALVE WEEN SATS OF FLOIT WAS (a) VARIABLE AND (b) COUSMT. Variable Rate of Flow Constant Rate of Flov Type Rate Maximum Mean D.T op in Drop in of of pressure pressure ir. ich.ec inc. hes valve flow drop drop W9 .ter wat er L/M Inc »HgO Inc, H 2 wLian rate whe n rate was 60 L/M was 1Y0 L/M Old Flut-63.1 3.34 1,18 1,0 3,1 ter New Flut-61.5 lc40 0,6 0:55 2.7 ter Old Good-61.5 1*25 0,5 0o7 1.3 rich New Good -6 8.0 0,3 0.25 0.1 0c2 rich NOTE* Data for variable rates of flow were obtained by taking a mean of from 4 to 5 exhalations. - 130 - T^ST BY JPICHAMCAL .MPAKS The mechanical methods for testing the valves in many respects was more accurate than that used in the man test. Two types of apparatus were employed in these tests; first, an apparatus which provides for an intermittent flow of air (the Goodrich valve testing machine) ; and, second, an apparatus which gives a constant flow of air. Apparatus and Methods: First: The intermittent air flow machine or Goodrich valve testing machine. (See Plate XXXII). This apparatus is essentially a mechanical breather, consisting of a motor-driven piston pump. To the cylinder of the pump is attached fittings so that air is drawn in through a valve and forced out through another; i.e., inhalation and exhalation valves. A gage to register the pressures obtained in the cylinders consisted of a rubber tambour , so arranged that changes in pressure in the cylinder would produce movements in the tambour which is recorded on smoked paper by means of a writing pointer attached to the rubber membrane. The devia- tion of the pointer at known water pressures is determined at short intervals. The pump is arranged to be run at two speeds. The slowest rate delivered 29.5 liters per minute at a speed of 22.5 r.p.m. The faster rate is obtained at a speed of 63 r.p.w. and a delivery of 82 liters per minute. Since the pump gave - 121 - an intermittent flow, air is delivered only half of the tine; therefore, the actual delivery of air is at a rate of double the above figures or 59 and 164 liters per minute. However s the flow of air from this pump was not uniform, since the max- imum velocity of the outgoing or incoming air occurred when the piston was in the mid-position of the cylinder (the piston being p^0p4lled by an 1 eccentric on the wheel of the motor gave a surfc durVe) . The maximum velocity of air when the pump was going 28.5 i»»p.m* per minute is about 80 liters per minute and at a rate of 63 r.p.m, or 226 liters per minute. Therefore, the peak of any curve shown represents the pressures obtained at 80 and 226 liters per minute, exhalation velocities which correspond to that obtained in moderately and extreme exercise. Second: The constant air flow machine to determine flow resistance of valves. The apparatus is shown in figure XXXIII. Air is taken from an air line of the laboratory and by means of a balancing tank and pressure g3.g^ , etc. kept at a constant pressure and rate of flow determined by a flow meter. A fine adjustment needle valve regulated the flow of air through the flow meter. An Ellison differential draft gauge determined the resistance in water pressure. The valve or fitting to be tested was at end of pipe as seen in cut. In operation the fine adjusting needle valve is set to a predetermined rate of flow and main- tained by a check reading on the flow meter gauge. - 132 - 3* 3! & h f- ft r > o X o. m -t» 5 53 5 3= 3 ss?s (A *** r- * O in "0 o 2 — i H oJ O •*> > r :> M r~ h r~ m 5 D 3) O C* o ~~ 5s P Pi > m < CD — < 3D 1 > % o 5 c o o to Z fcH 1-3 RESISTANCE TO FLOW APPARATUS PLATE XXXIII A AUTOGRAPHING MACHINE PLATE XXXIII B A reading of the res.is bancs offered by the fittings without a valve is first t alien on the Ellison gauge, the valve is then attached to the fittings and a second reading of the Ellison gauge is taken. The difference between the two reading represents the resistance to flow of the valve under test. Object o f the Tesb ; Since two important points in the matter of resistance are; (1) force required to unseal, and (2) force required to maintain the opening, tests were made to determine the value of these forces by the use of the above described apparatus. Resistance of Valve Fitting s: Since the mountings of the valves are responsible fcr a good deal of the resistance to the exhalation resistance, tests were made at various rates of flow with the various types of fittings used in the various masks. The following table gives the resistance found; first, by the constant flow machine , and second, by the intermittent machine , HKSISTAECS OF MA3X FITT7NGS WITHOUT MASES- CONSTaWT FLOW Rate of Flow Liter per Min. 5/8' f Round 3/4" Round 7/8" Round R.F.K, A.T. 85 120 150 200 - 133 .05 .0 ,0 .5 .14 * * .06 .0 1.10 . 3 .4 .1 .0 1,70 . 5 .7 .2 .0 3.14 .83 TEST OF RESISTANCE 0? VA.L7E ^I'.'^IHGS BY INTERMITTENT AIR ?LOW MAC IINE (Plow 29.49 liters per minute - laximum velocity 80 Li.). Fitting 7/8 G.L, .15 (see curve I Plate XXXIV A.T. .35 " " II R/F.K. .95 " " III " RESISTANCE OF VALVES TOST - , CONST A.NT fLOff ; - The Goodrich valve made up with thin and heavy walls and in three sizes - 7/8 ,: , 6/8" and 5/8" diameter - together with the new Ho. 5 Flutter, Standard Flutter and English Flutter, were tested; first, with various rates of constant air flow which gave the following results: RATE OF AIR FLOW - LITERS P^R MINUTE Type of Valve 85 1 20 150 200 Inc. of W. Hes. Goodrich 7/8" Thin Wall Goodrich 7/8" Heavy Wall Goodrich 3/4" Goodrich 5/8" Ho:. 5 Flutter Standard " English " .38 .£■5 .27 .16 .71 .75 .75 .73 ,61 .73 .-85 1.22 ,87 1,70 1.64 1,39 .12 .14 .06 .08 .54 .75 .73 .88 .40 .46 .45 .71 SECOND - INTERMITTENT FLOW:-- With intermittent air current in order to determine the opening pressure and the sustained pressure when the valves are dry, wet amd moistened - 134 - O — . ~*=£^ £>/-v two tests were going 22„b r.p.m. and delivering 29.5 liters per minute, the maximum velocity obtained being about 80 liters per minute. Table OPFNING PRESSURE SUSTAIEIHG PRESSURE Type of Valve Dry Salivated Glycerined Dry Sali- Glyoer- vated inad B.F.G. 7/8" Thin Wall .15 .51 .54 .15 .30 .25 B.P.G. 7/8" Heavy Wall .30 11 11 11 B.F.G. 3/4" .95 .85 1-10 1.10 1.00 1.00 B.F.G. 5/8" 1,20 1.7 2.4 1.70 1.5 1.65 No. 5 Flutter .01 .53 1.01 .20 .3 .3 Standard .22 1.8 1.6 1,00 1.6 1.0 British .48 ,55 1.4 .65 .85 .85 -r 7/8" heavy wall mold changed to thin wall because of high resistance due to thickness of material. A second test on the Goodrich testing machine with glycerined valves gave the following: - 135 - Table PUMP MAKING 22.5 r.p.m. = 29.49 LITFRS P?:R MINUTE - MAXIMUM AIR VELOCITY OBTAINED ABOUT 82 LITERS PER MINUTE. Exhalation Valve Resistance in Resistance inches of water of fitting Regular Flutter #5 Flutter Goodr i ch-Lakesi de 7/8" Light Wall 1.25 .50 A.T. A.T. .35 .35 .475 (7/8" G-L) .325 True Resist- ance of valve o90 .15 .150 PUMP MAKING 63 r.p.m. = 82 LITFRS P^R MIKUTE - MAXIMUM AIR VELOCITY OBTAINED ABOUT 22.5 LITERS PER MINUTE. Exhalation Resistance in Resistance True Resist- valve inches of water of fitting ance of valve Regular Flutter #5 Flutter Goodrich-Lake side 7/8" Light Wall 3,9 2,65 1.25 • 35 .325 3.55 2,30 .925 Curves given in plates XXXV and XXXVI give a very good idea of the relative resistance offered by the valves. Adjustment of Goodrich Valv es:- In the case of the Goodrich valve, a special cage was made to vary the distance between the valve and the valve seat. With this the tolerances in setting were determined within which no serious variations occur, whether in the opening pressure, sustaining pressure, flow resistance or leakage. It was found that a total of .15" was permissible - .05" extension plus .10" compression. It is not possible to exceed these limits with the type of mounting used, - 136 - +05 0* -o-y < ^ U © <0 In 40,5" X ci *E -0.5 GOODRICH LAKt VKWE Nri«y\©ER 6 FLUTIER VALVE P f/O" -er S T Utter V a l/e. Curve Mo 3 Regular Flutter V A 2v*. 7 LATE XXXVI Relationship of Thickenss of Rubber Stock in Valve t o Resistance to Flow : - Where two valves are ox the same type of con- struction, the resistance increases in direct proportion to the thickness of stock. A Kops valve made from .016" stock showed .13" resistance, against .40" resistance when made of .040" stock, both tested at 85 liters per minute. CONCLUSIONS 1. At the rate of 29.49 liters per minute, the Goodrich-Lake side 7/8" light wall valve offers least resistance; the A.T. is second, and tke S.if.K. a poor third. 2. At the rate of 29*49 liters per minute, the Goodrich-Lakeside 7/8" light wall valve offers the least resistance; the Flutter #5 is close second, and the regular Flutter is third. 3. For the valves at 82 liters per minute, figures for fittings plus valves are available. In this case the Lakeside-Goodrich 7/8" light wall offers least resistance; the Flutter #5 second, and the regular Flutter third. - 137 - PART II Subject : Valve Leakage. Object : To determine valve leakage under various conditions. Apparatus : Plate XXXVII and Plate XXXVIII. The valve (2) to be tested was placed in a air-tight chamber (1) and this was connected by tubing to a bottle in which a positive pressure of air could be maintained by a pressure bulb , the pressure being determined by a water manometer. The pressure of the chamber once established it can be maintained if any air leaks out of the valve by adding a measured amount of water to the pressure bottle, The amount of water required to be added per minute to the pressure bottle is the leakage of the valve per minute. The valves were tested when dry, wet, glycerined and dirtied in this apparatus at pressures corres- ponding to from &'■ to 1" vacuum. The following tables give the results of the test: Table Dry ^ Salivated Glyjerixied Type of Valve 6" 4" 2" 1" 5" 4" 2" 1" 6" 4" 2" 1" B.F.G.7/8" Thin Wall .5 .2 1 3 2.1 .4 .0 No. 5 -|- 380 300 400 30.9 22,3 27.7 14.8 Standard -f- -j- -j- -f~ 73 67.5 56. 19.8 -+- -|- -J- •+- British Type 22.3 14. 9. 5, 14.7 12. 6.4 2.6 1.1 1.3 .4 ~t- Leakage too great to get reading. - 138 - LEAKAGE APPARATUS PLATE XXXVII \ rHtww ^t^fcwy w^fc^ > X X X W H P-, % «K ** ^ *t h ■ * <$ o"" K <* M K « % 4 <& 5' '■*"*, «C =4 «3 iy fr- ee 3-1 X * S » £ *• ® A **., X^ 'O *» & -l E K«i A. ^ *S| SV? 3 hlu«u Ut *) > ~ K Hi cr -4 a: «* fee £r ^ r* ** v<\<»]^ ^ 9 5 ! *j ^ ill -si These figures are probably in excess of a true average for a given type. Instances have been noted where, for example, a So. 5 valve will show no leakage when tested wet, but on a check test the same valve will leak considerably. Failure of the water to form a perfect and uniform film over the surface of the valve is the most credible explanation of the discrepancy. LMKAGE IN TERMS OP 0,0. OH 1 AIR PKR MIMUT'S Valves rubbed in sandy mud and water , thoroughly dried and cleaaed as much as possible by violent blowing and beating. ^RTISDJTALVKS V alv e _ _ 7/8" Thin Wall, 6" Vac, 4" Vac. 2 ,J Vac. 1" Vac. normal setting 30. S 38.7 420.0 over 400 No. 5 A.T. Pitting Leaks too great to get reading Regular A,T, Pitting Leaks too great to get reading CONCLUSION With clean valves, dirtied valves or salivated valves the Goodrich type of valve gives the smallest leakage. - 139 - PART III Subject : Durability of Valve. ObjjBct : To determine the comparative durability of valve types. Method and Apparatus: A 7/8" Goodrich valve and a No. 5 Flutter valve were fitted on the cylinders of the Goodrich testing machine (see diagram) , and this machine was run con- tinuously until each valve had made 3000 exhale movements. During the test a number of valves were removed at successive intervals and tested for leakage and resistance by the Goodrich leakage apparatus and resistance apparatus (see following dia- grams) . The resistance tests were made at the rates of 85, 120 and 200 liters per minute. Valves tested dry for leakage. Exhalation at rate of 22.5 per minute. DURABILITY TEST 7/8" Th in Wall Resistance Le akage c'c.per n: 85 120 150 200 6 "vac. 4" ~ 2" ~T"~ At Start of Test .39 .32 .29 .16 .9 After 26150 Exhalations .39 .35 .29 .16 .0 After 54490 Exhalations .40 .37 .31 .16 3.7 After 86885.40 .37 .29 .17 .0 " 117040.41 .39 .32 .16 .0 " 144928.40 .28 'Z'X .16 1.5 " 177050.40 .37 .31 .16 .0 " 208315.40 .34 .33 .17 .0 " 238330.38 .35 .27 .17 .0 " 300000.42 .35 .31 - 140 .16 .0 A .0 .0 .0 .0 .0 2.2 .0 .0 c Ho. 5 Flutter - A.T. Fitting 85 Re 120 sista 150 .nee 200 .10 Le 6 "vac. akage 4" c.c. p 2" er min. 1" At Start of Test .22 ,20 .34 74.8 69, 54.9 38.6 After 86150 Exhalations .20 .24 .18 .15 102, 96 74. 43.0 After 54490 .22 .20 .15 .11 25.4 19.9 12.5 8,8 " 85885 .25 .23 .11 .10 44.2 43.1 32,2 20.6 " 117040 .18 .16 .10 .06 13.9 11.9 8. 6.8 " 144928 .19 .16 .10 .06 18.7 15.5 12. 6.7 " 177350 = 25 ,19 .16 .16 25.5 20.8 16. 11.4 " 208315 .22 .21 .15 .12 69.5 57.1 32.4 18.3 " 238330 .29 .28 .20 .17 17, 10.9 11.1 8.5 " 300000 .27 .21 .20 .15 22.1 18.7 14.3 11.4 CONCLUSION There is practically no change in the resistance or leakage in the Coodrich type of valve. In the flutter valve there i3 no change in resistance and there is a slight decrease in leakage. Apparently either type of valve is durable enough for practical purposes. 141 - PART IV. Subj ect : The effect of cold upon valves. Object : To obtain comparative data of effects of heat and cold upon Goodrich and flutter types of valve. Method and- Apparatus : It is extremely difficult to devise a method to determine the affect of cold upon valves which would simulate actual conditions on the field. It is impossible to obtain low enough temperatures in cold storage to put the valves to a severe test. In attempting to do this by freezing mixtures , the warm air passing through the valve raises tb^ temperature in the cold box, and the conditions of using a sample of the outside atmospheric air are not simulated. Serious attempts were made to solve this problem, but the data obtained do not apply to actual field conditions. The volume of constant flow in both the flutter and Goodrich valves was increased, as shown by the following table. There was likewise an increase in leakage, However, these low temperatures would never be reached in acoual conditions, for the warm air exhaled from the lungs would keep the exhale valves away above the temperatures reached in the experiment. Neither would the pause between the exhalations be great enough to allow the valve to lower its temperature to any marked degree . Observations ', - 142 - Table resist ance: to plow Temp. 7/8" Goodrich ho . 5 Peg. P. 85 180 "~TBG~ ' 200 85 120 150 200 62 .34 .55 .35 ,25 .46 .65 .80 1.15 32 ,37 ,36 .31 .32 .48 .66 .82 1*20 .54 .62 .96 1.07 .55 .74 1,01 1.54 -10 .62 .72 1.14 1.52 .74 ,85 1.40 2.24 - : LEAKAGE Temp, 7 /8" Goodr ich So. 5 Deg. P. 6" 4 I: 2" *" 1" 6" 4" ' 2" 1" 60 22. 21. 18 16 32 26. 24. 20 19 6 200 250 250 300 -I- -I- ~»- -1- -I- 4- -!- -J- -I- -(- -I- -i- -10 -i- -h ~t- -I- -h -t- -t- -1- -j- Leakage too great to get reading. The time taken for the valves to "thaw out" after being wet with water and then frozen was as follows: Goodric h 7/8 " Ho. 5 15 se3 20 n 10 IT 18 1! Av e. 15.7 sec. ' CONCLUSIONS 30 sec 35 IT 25 ,T 30 ft Ave. 30 see. Cold has less effect upon Goodrich than upon flutter valves. - 143 - PART V T he, effect of c ure f or manufacturing purposes: It tfas considered necessary to determine what degree of variation in the cure of a valve might be allowed. A few 7/8" thin wall valves were given over and under cure , equivalent to 16 per cent variation from optimum , with the expectation that if there were any marked differences shown , a complete set of ail types of valve would be made up and tested, The results of these cures , as compared with a norma?. or standard cure, do not show any variation, and the belief appears to be justified that any other type of valve similarly cured will not act differently, Life o f rubber : Since the life of rubber can be accurately determined by subjecting it to heat at low tempera- ture in an oven for various periods of ti.iae, it was thought wise to determine the life of the valves by this method. Accordingly the various valves were placed in the life oven for periods of one s two, four, sir, ten and twelve days, and their leakage test was determined. It was shown that from the effect of age as determined by the life oven, the valves did not appreciably deteriorate in a reasonable time, possibly up to eight months or a year. O'hINFRAL SIMMARY The "rating" of each type of valve as given below is admittedly arbitrary in several respects, but as far as - 144 - possible the valves assigned have been calculated from numerical data. Type of valve Opening Flow Leak- Dura- Cold Cure Pat- Resist- age bility ing ance Dry 95 90 100 95 80 Goodrich 7/8" x if" Thin Wall 90 95 100 Goodrich 7/8" x if" Heavy Wall 80 60 100 Goodrich 3/4" 70 80 Goodrich 5/8" 40 30 Ko.5 Flutter 100 98 Standard 85 80 English Type 75 95 75 Goodrich 7/8" x *■» Thin Wall 95 98 100 95 80 75 35 100 80 55 80 --- 97 CONCLUSION AUD ?^C0MKENDA.TI0K Since laboratory data show that in many respects the Goodrich type of valve is superior to the flutter, it is recommended that extensive field tests be made of this valve, under actual conditions, to determine its fitness for adoption. - 145 - EXHIBIT XXV Subject ; Absorption of ohlorpicrin by A„T. and K.T, face pieces, Objejrt: To determine what becomes of ohlorpicrin which leaks into A,T» and K,T. masks. Introduction ; As shown in the above experiments of Exhibit XXII , ohlorpicrin may leak into a mask and not gas the subject. To esti^iate small concentrations of cblorpierin, the technique which is described as Exhibit XVII was evolved, and the following experiments utilizing this method were conducted. Apparatus and method : Apparatus for obtaining known concentrations of ohlorpicrin was described in Exhibit XVII. K.T. and A.T. masks were provided with breathing tubes and fitter* to subjects. The dead space of the masks was determined by water displacements , and known concentrations of ohlorpicrin were in- troduced into this space by plunging a fine hypodermic needle through the face pieces, The subject kept his eyes tightly closed, and opened them at the expiration of one, two, three and four minutes, The concentrations placed in the mask were 30 parts per 1,000,000, the upper range of our physiological method of estimation. The time required for the ohlorpicrin to compel the subject to close his eyes after he opened them at minute intervals was accurately taken, and by references to the subject's own eye-sensitivity calibration-curve previously worked out, the concentration of cblorpicrin in the mask was known. To make certain that the injected gas was thoroughly - 146 » mixed with the dead space air, che subject shook head vigor- ously during the 15 seconds immediately .following the injection. Amplifications of the general idea were mcde in determinations on dry and moist face pieces , and on parts of face pieces in- closed ill a glass tmib so that determinations could be made with stronger concentrations and over a longer period of time. ABSORPTION OF CHLORPICRIM BY RUBBER Vol. of Bulb, 7 35 c.c. Time of 19 sq« in. Same 32 sq.= in.> Same 144 sq.»in. exposure A, T*face sample A. T.face sample i/ie i" rub- Pi ece repeated Pi ece repeated ber bcse At start 50 50 50 50 50 1 min. 30 10,5 13 4.5 2 min. 20 6.5 7 1.0 3 min. 16 15 3,5 Less than 5 5 min. 13 13 3,0 »f 10 min. 7. 5 10 2.5 -- — 147 - ABSORPTION OF CFLORPICRIN BY K.T. PACE PIECE < Time in Subject tfubj^t Subject Subject Subject Subject mask T.M.R. A-Pc A.P* T.McR. T*M,R. A,?- p.p. in. p.peau p. p.m. Mask wet Mask wet Mask wet p o p m. p»p.mo p?p c m. At start 30 30 30 30 15 30 1 min. 16 13 18 -- 7.5 -_ 2 min. 7 -- __ 15 3.0 -- 3 min. 4 4,5 4 13 2.0 10 4 min. 2 2.5 2 11 -- -- 5 min. -- — __ 7 -- 5 ABSORPTION 0? CHLOEPICAIN BY A.T. PACE PIECES Time in mask Subject T.M.Ra p. p.m.* Subject A, P. p*p.m. * Subject A.P. p,p.m«* Subject S.P.R. p. p.m. At start 30 30 30 30 1 min. 20 20 7 7 2 min. 16 12 4 4 3 min. 7.5 -- 1.5 4 min. 5 Less than 5 5 min. 3 * Mask wet . - 148 §3 to I « Q & < £ 5 I I s x x X M < c/ - digyozgma sz-e Conclusions 1. A.T. and X.T. face pieces absorb chlorpicrin at approximately the same rate. The rate of absorption may be expressed by stating that a concentration of 30 parts per million is absorbed in five minutes in sufficient quantities to allow the eyes to remain open - that is, to less than 1 part per million* 2. Moistening with water greatly r^auces the absorp- tive power of the face pieces for chlorpicrin. 3. The amount of absorption by the rubber face pieces is enough to explain our results. The possibility that the skin of the face absorbs chlorpicrin is present , but has not as yet been investigated* 4» This work, in conjunction with the work reported in Exhibit XVII, satisfactorily explains why a mask may leak and yet provide protection to the wearer, NOTE: The experimental conditions in these tests are much more severe than those met with when a subject is actually wearing the mask in gas. The leak-in in the latter case, excluding "gross leaks, is through fine capillary openings., the walls of which consist of the skin of the subject and the rubber of the mask - ideal conditions for absorption, Ary unabsorbed gas is promptly and enormously diluted with the entering inspired air. - 149 - EXHIBIT XXVI Subject : The resistance of corrugated tubing. Objegt ; To measure the resistance offered to breathing by the corrugated tubing connecting the mask with canister, and to compare it with the resistance obtained with an equal length of Goodrich tubing. Apparatus : Plow meter manometer. Meth od and procedure ; The chief advantage of the present rubber connection used in the gas mask is its extreme flexibility. To accomplish this desirable quality, corrugations are necessary in order to obviate the danger of kinks during bending or twisting of the rubber-hose connection. It is obvious that the ridges caused by these corrugations offer a certain amount of resistance to breathing. The object of this experiment was to measure this resistance and then to determine that of the straight Goodrich tubing under exactly similar conditions. -- 150 - COMPARATIVE DATA OBTAINED OK GOODRICH TUBING. AND CORRUGATED TUBUS 3 Kind of Dimensions Description Length Shape Flow Drop tubing of tubing of piece when Liters Inc. tested tested p 4 m» H2O Corru- Inside Tubing covered 21 Hori- 85 1/8 gated diam. 13" with thin but very zontal " rs" dense layer of cot- 90^ 1/8 Outside ton fabric. Tubing 180° "bend"" 1/8 diam.lt-" soft and very flex- ible; stretches Borl- and "gives" very r,ontal 175 9/16 easily. 33 corruga- 90° " 5/8 tions per foot. 180°"b^nd" 7/8 Goodrich Inside Tubing is quite 21 Hori- 85 Beglig- diam. 7/8" rigid. Does not zontal ible stretch appreciably 90° " " Outside even when large 180 " diam. force is applied. (long sweep) 14" Impossible to make 60 deg, without Hori- 175 3/8 formation of kink. zontal Layer of cotton 90° " " fabric just beneath (long sweep)" rubber surface, Summary At a flew of 85 liters per minute, the resistance of the flexible tubing was only l/8 inch, Bbrtding the tubes at right angles or even 180° caused no appreciable increase in the pressure drop. With the straight Goodrich tubing under similar conditions the drop was practically nil. At a flow of 175 liters per minute, the Goodrich tubing gave about 30# less than the present corrugated tubing. - 151 - However, *»ven at this high flow the pressure drop of the corrugated tubing was only 9/l6 ,; . Cono lus i ons Whilp the straight Goodrich tubing has less resist- ance than the corrugated tubing, the physical properties of the latter are such that their continued use is highly warranted 158 - EXHIBIT XXVII RATING CHART TOR GAS MASKS Object: To secure a fixed method of rating masks based upon specifications, from a physiological, mechanical and production standpoint (which it has been shown a mask should have). The different points of the specifications are rated according to relative importance, as discussed in the foregoing: report: RATE CARD 0? MASK Total Value of Value of points sub- sub- i terns items 1 2 I. Leakage .100 II . Physiological ratin g 100 A. Breathing requirements 45 1. Resistance to inspiration . .. 12 2. Resistance to expiration... 12 3. Respiratory efficiency 21 (dead space) B. Visual requirements 30 1. Range of vision 15 2 . Dimming 15 C . Comfort 25 1. Pressure of mask to prevent leakage 15 2. Boredom ." 10 100 100 100 III . Mec hanical rating 100 1. Materials of construction 5 2. Manner of producing gas-tight face fit, heed bands and ad ius tment 30 3. Inhalation tubes 10 4. Anti-dimmin/? 15 5 . Exhale valve • 15 6. Eye piece position 25 100 100 (153) ' IV. Rating of flarr ie? -i and_jrubj.ag 100 1. Pcsitiem of. carrier ....... i ...,., .60 a. Convenience and ocrofort of carrier ........... s .... „ 10 b. Free lc;m of body movements , 25 c. Protection of tube and cani st er xo d. Accessibility of mask ...;.. 15 2. Tube 25 a. Length of tube and direction of air current ,.*.. 12,5 b, Fixation of tube to face 12.5 3« Service specifications of carrier 15 15 100 100 100 V. Production rating , 100 1. Volume of production 20 2. labor of production 20 3. Inspection 20 £. Rejects 20 5. Cost 20 100 100 Conclusions By means of foregoing chart a fair rating of a mask can be secured L >■ 154 - APPENDIX A PRELIMINARY SURVEY OF THE PHYSIOIOGICA T VICTORS WHICH MUST BE CONSIDERED IN GAS MASK DESIGN, AND THE IMPORTANCE 0? THESE FACTORS TO THE SOLDIER MAJOR R.G. PEARCE, PHYSIOIOGICAT, LABORATORY, LAZES IDE HOSPITAL, CLEVELAND , OHIO . SEPTEMBER 20. 1918 - 155 - T ABLE OP CONTENTS I. The factors which contribute to the delinquency of the gas mask and canister. (1) Resistance to breathing. (S) The volume of air which must be re breathed, (3) The general discomfort of the mask. II. The physiology of respiration, with special reference to the problems of the gas mask: (1) The oxygen consumption and carbon dioxide excretion of the body. (2) The normal respiratory rate, (3) The minute volume of air respired. (4) Gaseous composition of the air in the lungs and in the air passages. (5) Dead air space. (6) Relative time of inspiration and expiration. (?) Relationship of the circulation of the blood to respiration, (8) Psychology of wearing the gas mask. III. Physiological effect and relative importance of; (1) The dead air space of the mask. It is sho-vn that the importance of the dead air space of a mask lies in the fact that it increases the minute volume of air respired, Which, from a physiological point of view, is harmful for the following reasons; (a) Dead space affects the carbon dioyiie content of the blood and thus reduces the reserve efficiency of the tissues. (b) Dead space increases the volume of air which must be pulled through the canister - It has the sans effect as increasing the resistance of the canister, since this is proportional to the volume of air flowing through it. (c) The reciprocal relation between the dead air space and resistance is pointed out. (d) It is known that the life of the canister depends on the volume of the gas -laden air which passes through it. The dead. space increases the volume of air breath* 3 It therefore decreases the life of the canister . - 156 - (2) The effect of resistance to breathing through it and the effset of increasing the resistance to respiration on: {!) the blood pressure; (2) the right heart; (3) the blcod and lymph content of the lung; (4) the minute volume of air breathe- (3) The effect of canister resistance on the rate of air entering the lungs and on the length of the inspiratory and exniratory periods. The gas mask at best is an undesirable piece of wearing apparel. It is the duty of the physiologist to determine "'hat factors contribute toward making it such, and to place an estimate on the relative importance of each, so that the design of the mask may be scientifically and efficiently planned. The Physiological Laboratory at lakeside Hospital, now under the Chemical Warfare Service, Medical Division, has arranged its ™'ork «"ith these objects in vie"'. On a priori grounds we believe that three things rail J - ta-te against the efficiency of the gas mask; (1) the resist- ance which the mask and canister offer to inspiration and expiration; (2) the amount of expired air which must be re- breathed because of the dead air which remains in the mask and its tubes following expiration; and (3) the discomfort of the mask because Of the harness, interference with vision, and similar factors. In order to evaluate the importance of the above factors, it is necessary to discuss the physiology of respiration, and its relationship to the circulation of the blood and to the central nervous system. - 157 - PHYSIOLOGICAL ?ACT3 0? INSPIRATION The oxyg en co nsumpt io n a nd carbo n dioxide exc retion of th e bod y. - The function of the respiration is to deliver oxygen and to remove carbon dioxide from the blood as it passes through the lungs. During rest a man uses about 250 to 275 c.c. of oxygen per minute. ?our per cent of the ex- pired air is carbon dioxide » When a man is walking at the rate of four miles an hour, he uses about 1050 c.c. of oxygen per minute, and running at the rate of five and a half miles an hour, he uses about 2100 c.c. of oxygen per minute. The carbon dioxide produced by the body tissues and eliminated through the lungs per minute is slightly less than the above figures for oxygen in each of the above cases. The disparity between carbon dioxide excretion and oxygen consumption is due to the fact that the oxidation of foodstuffs requires some oxygen to unite with the hydrogen present, and the oxygen is eliminated as water. The ratio of the carbon dioxide excreted to the oxygen absorbed per unit of time is xnown as the respiratory quotient. The norma l respir atory r ate . - The rate of respiration is subject to great individual variation. At rest a man breathes 10 to 18 times per minute, while walking the res- piratory rate is not greatly increased. While running *ive and a half miles an hour, the respiratory rate in our series of cases averages about 22 per minute. It must be remembered, - 158 - however, that when the subject's attention is called to his respiratory efforts, unknowingly the rate may be mark- edly varied, snd in fact usually is. 1,'Iinute volume of air respired . - The volume of air breathed at rest varies between 5 and 9,5 liters per minute. When walking 4 miles an hour, a man breathes from 17 to 22 liters per minute, and when running 5% miles an hour, he requires 36 to 42 liters oer minute. The variations which occur in the volume of the respiration in different individ- uals doing the same amount of exercise are due to individual factors, among which it might be stated are: the rate of restoration, the response of the heart to exercise, the decree of "training" of the individual, the surface area of the man's body, the time relation to digestion, and the quality and quantity of the food orevicusly consumed. It will be noted that there is a strict parallelism between the amouit of oxygen required and the minute volume of air needed to bring that quantity of oxygen; e.?., from the following data taken from actual experiments, it will be seen that the ratios existing between the minute volume and the oxygen consumption at rest, walking and running are practically the same. Min,vol. of air 6050 Oxygen consumed per min. 275 ~275 = 22.0 Rest 19000 ~ 18.1 talking \ Aver age 1050 of 7 39000 2100 - - 18.55 Running - 159 ~ While this strict parallelism between the increase in consumption of oxygen and increase in minute volume of air breathed holds at moderate degrees of exercise or during work which can be sustained, our experiments have shown that the parallelism is lost at higher levels of oxygen consumption or at levels of work which can be maintained only for a limite- period of time. In this case the minute volume of air is in- creased out of proportion to the increase on the oxygen needed to perform this excessive work. The ratio existing between the minute volume of air breathed and the oxygen consumption is increased. This increase may amount to 50 to 90$ during extreme muscular effort; for instance, in the case of E.G. P., when he is consuming 2700 c.c. of oxygen per minute, his minute volume of air is 72 liters - a level at which work can be main- tained for only a ?ery brief -period. During extreme work the minute volume rose to over 100 liters, and the oxygen con- sumption was 3000 c.c. Kin. vol. of air 72000 Punning at top speed for = 26 ° 7 230 vards. Air samples Oxygen consumed 2700 taken during last third of run. " " 1000 ° = 33.3 Most violent work. 3000 To recapitulate, during extreme exercise we have a ratio of 33.3 as opposed to the foregoing ratio of 18. The gaseous compositi on of the air in the lun gs and in the air passages; and deafl air space . - As previously stated, the function of the respiration is to bring oxygen to the blooi - 150 - and remove carbon dioxide; and while the respiratory appar- atus includes the mouth, nose, pharynx, trachea, bronchi, bronchioles and lungs, it is only in the lungs, in small terminal air sacs - the alveoli - that the exchange of these gases takes place. In these air sacs the air is separated from the blood by a very thin membrane, through which oxysren readily enters into the blood and through which carbon diox- ide readily passes from the blood into the air. Therefore, from the standpoint of gas exchange the air sacs, or alveoli, are the important part of the respiratory tract, but the bronchi, bronchioles, trachea, etc., also play an important part in our problem. Since no gaseous exchange takes place in these cavities and passages, they are called the dead space, and the air which occupies them is called the dead air. This air must be pushed out at each expiration before air which has been in close contact with the blood can be expelled likewise, the air which remains in the air passages at the end of the expiration must be drawn into the air space of the lungs, the alveoli, before fresh air can be taken in during inspiration. Theoretically this lead space air, being atmospheric air, contains no carbon dioxide and has the nor- mal atmospheric percentage of oxygen at the end of inspiration; at the end of expiration it contains only air having a hiffh carbon dioxide and a low oxygen content, since it has been in the terminal air sacs of the lungs. This beinsr the case, the total expired air contains a lower percentage of carbon , - 161 - dioxide than the air which is in the terminal air sacs - that is, the alveolar air. The capacity of the anatomical dead air space is estimated by most observers as being from 100 to 150 c.c. There is some evidence that dead air space may be increased in deepest breathing by 75 to 100 c.c, but there is not the slightest evidence that the increase is ever greater than this. Since the blood and the air in the alveoli of the lungs are separated by only a very thin membrane, the carbon dioxide in the blood is given off in sufficient quantities to bring the carbon dioxide in the air into equilibrium with that of the blood as it leaves the lungs. Under ordinary conditions of oxygen consumption, the oxygen taken up by the blood will be proportional to the carbon dioxide given off by the blood. Any change in the amount of carbon dioxide 'f'hich the blood contains ""ill therefore bring about a change in the amount of carbon dioxide in the alveolar air, and vice versa . It is this carbon dioxide in the blood -which controls the impulses arising in that part of the brain -vhich has to do "'ith respira- tion, so that the respiratory exchange is increased or decrease?. according to the amounts of carbon dioxide formed in the body. Thus a more or less fixed concentration of carbon dioxide is maintained in the blood. The automatic control of the respira- tion is provided for by both a nervous and a chemical mechanism. The depth and volume of the individual respiration probably is under a nervous control, while the total ventilation of the "- 162 - alveoli per unit of time is governed by the concentration of carbon dioxide in the arterial blood bathing the center in the brain which controls respiration. The authors are of the firm belief that the carbon dioxide anion has a direct effect on/the respiratory center independent of its effect on the hydrogen-ion concentration in the blood (R.W.Scott). An increase in the percentage of carbon dioxide in the alveolar air is attended by an increase in the respiratory volume. At ordinary levels of oxygen consumption, an increase of from 0.2 to 0.3$ of carbon dioxide in the alveolar air will bring about a 100$ increase in the minute volume of the respiration. In walking four miles an hour, the respiratory minute volume is increased 400$. This would mean an increase in the carbon dioxide percentage in the alveolar air of about 1.0$. Tbis change has been found to occur by the senior author by actual experiment. If the capacity of the air passages is increased, as stated above, the respiration must also be increased in volume to provide adequate ventilation. This is automatically taken care of by a piling ur> of carbon dioxide in the alveolar air and likewise in the arterial blood and venous blood in amounts sufficient to stimulate the resoiratory center in the brain to provide a proper minute volume to keep the gas exchange of the body adequate to its needs. The average percentage of carbon dioxide in the alveolar air at rest may be taken to be about 5.2. The mean average - 163 - composition of the expired air is about 4^ carbon dioxide. The difference in the oercentage comoosition of alveolar and expired air is due to the diluting effect which the dead air has on the alveolar air. (The volume of the respiration is 500 c.c; the volume of the dead space air therefore w ould be (500 x .04 500 -» = 116 c,c, which is the volume of the dead air soace) . THE REIATIVE TITIE 07 INSPIRATION AND EXPIRATION Normally/ at rest the length of the resoiratory cycle varies ,Fr ith the individual. In all cases thus far studied the length of inspiration is from 30 to Z>5% of the total cycle. Expiration is generally somewhat longer, averaging- 40 to 45$ of the. total cycle. Toll-owing expiration and inspiration there is always a period of rest. The rest period following expira- tion is usually quite pronounced, amounting to about 20 to 30 vo of the respiratory cycle. The rest following inspiration is 10 to 15'c of the respiratory cycle. Einoe the length of inspiration averages about one thirl r,a te of the length of the respiratory cycle, the actual volume /of air entering the lungs is three times the minute volume flow. That is, if the minute volume of the resoiration is 6 liters per minute, the air enters the lungs at a rate of 18 liters per minute . When a man is walking at a rate of four miles per hour, he is breathing about 20 liters per minute. In this case the - 164 - " length of the inspiration is 40 to 45$ of the total cycle; expiration is from 35 to 40$ of the cycle ana the rest period following exoiration is 15 to 20$ of the cycle. The volume rate of flow of air into a man's lungs while walking is from 50 to 60 liters of air per minute; expiration from 60 to 70 liters per minute. When a man is running, the inspiration is from 35 to 40$ of the total cycle, expiration is from 45 to 50$ of the total cycle, and the rest period is reduced to 10 to 15 per minute- When he is running and breathing at a rate of 40 to 45 liters per minute, the volume rate of air entering the lungs is, therefore, about 100 to 115 liters oer minute. The maximum velocity of air entering the lungs as tested by forced inspiratory effort varies with individuals; in our series it lies between 135 and 230 liters. RELATIONSHIP OF THE CIRCULATION OF THE BLOOD TO RESPIRATION. The function of the blood is to carry food to the tissues and remove waste products. Life can be sustained with- out food for forty days, and accumulated waste products in the case of urinary suppression can be maintained for ten days, but twelve minutes' deprivation of oxygen is sufficient to produce death or irreparable damage to the tissues. On these grounds we must believe that the most immediate function of the circulation is a respiratory one- - 165 - The volume of the bloodflow at r est is believed to bs about four liters per minute. This means that every 100 c,c of blood which leaves the heart must give to the tissues in its passage through them about 7 c.c. of oxygen, and must b-ir.. back to the heart a little less than this amount of carbon dioxide. When the consumption of oxygen is increased four times, as it is when a man is walking four miles an hour, tinier the amount of oxygen which is contributed by each, unit volume of blood be increased in amount, the bloodflow must be in- creased four times, and in this case the heart must deliver sixteen liters of blood per minute, furthermore, if the oxy^erj consumption is increased seven and a half times, as it is when running five and a half miles an hour, the blood flow would have to be increased seven and a half times (30 liters of blooi per minute), in order that the amount of oxygen delivered by every c.c, of blood be the same during the exercise as it is during rest. We must believe that the concentration of oxygen in the blood when it leaves the tissues, during a state of rest is the optimum for the tissues. It is, therefore, apparent tlv unless the bloodflow be increased in direct proportion to the oxygen consumption* the blood leaving the tissues will contain less oxygen than is optimum for the tissues. Since the amount of oxyg-en which the blood can carry is 20 volumes per cent - that is, 80 c.c. in 100 c.c. of blood - it is not possible for the oxygen consumption to be increased to more than three times that at rest without having some increase in volume of bloodflow - 166 - Such an increase, however, is never obtained, for even under the most extreme conditions the blood does not lose all of its oxygen in its passage through the tissues. Probably the amount of oxygen which each unit of blood contributes to the tissues in its passage through them never amounts to more than 12 volumes per cent, or three quarters of the total oxygen load of the blood. In this condition there is extreme air hunger and blueness. From the above remarks it is quite apparent that there must be a definite relationship between oxygen eonsupption and the minute volume of blood which the heart pumps in order that, sustained work be maintained. In other words, the rate of increase of ventilation of the air sacs of the lungs and the minute volume of blood leaving the heart are in linear proportion to the increased oxygen consumption or carbon diox- ide excretion of the body, or this relationship is closely approached. Whenever the ratio existing among the volume of bloodflow, the minute volume of the respiration, and the oxye-en consumption of the body is less than that existing among the same factors at rest, then we must assume that the tissues of the body are not bathed with blood having the optimum concentra- tion of blood gases. The ability of the heart to increase the amount of blood pumped per minute is more limited than the ability of the body to increase the minute volume of air respire or the ability of the body to use oxygen. In other "'oris, the - 167 - amount of work which a man oan do it not limited by his abil^ to get air or to utilize oxygen, but rather by the ability of his heart to pump blood according to the metabolic needs of the body. The phenomenon of getting out of breath is simply the reaction of the respiratory center to a blood supply which la not adequate to the metabolic needs of the body at the time , Since incompletely oxidized substances which are acid in nature act as stimuli to the respiratory center, a bloodflow which is not sufficient to carry away the carbon dioxide as fast as it is produced or to furnish oxygen rapidly enough to prevent the accumulation of incompletely oxidized substances in the blood, produces an increased respiratory minute volume and a respira- tion out of all proportion to the oxygen needs of the body. In other words, if the ratio of respiratory volume to oxygen consumption at rest is five liters of air to 300 c.c. of oxygen one would expect that -"hen 1200 c.c. of oxygen were being used the ventilation would be 20 liters of air, and "'hen 2400 c.c. of oxygen were being used, we should have 40 liters of air- In the majority of cases of untrained individuals or of even moderately trained men, when one is using 2400 c.c. of oxygen per minute, the respiratory minute volume in place of being 48 liters per minute may be as high as 65 liters per minute, the excess ventilation being thought iue to the substances in the blood. In this condition one finds the percentage of carbon dioxide in the expired air very low. This allows the blood leaving the lungs to have a lower percentage of carbon dioxide - 168 - than under ordinary conditions, so that a greater amount of carbon dioxide can be picked up by a unit of blood without the blood becoming unduly surcharged with the gas. It is quite apparent from the above discussion that a very definite relationship exists among respiration, oxygen consumption and circulation. Any factor that disturbs one is accompanied by disturbance in the other. Any factor which hinders the normal exchange of air in the lungs decreases the efficiency of the man by decreasing the reserve of his heart. If a man underventilates his lungs, then his circulation must be speeded up if the optimum concentration of oxygen and carbon dioxide are to be maintained in his tissues* If he super - ventilates his lungs, that is, breathes more air than is re- quired, the bloodflow can be decreased and still maintain the optimum gaseous concentration in his tissues, THE PSYCHOLOGY OF THE MASK The discomfort and other emotional factors due to the pressure of the mask; the effort involved in respiration; the limitation of the field of vision, etc.; and the fatigue due to' prolonged subjection to these conditions - are undoubtedly serious matters, affecting not alone the morals of the soldier, but also his efficiency in the various tasks required of him. The exact effect of these conditions upon the attention s memory, fine motor coordination fas in aiming a gun), and discrimination in perception and judgment, should be determined - 169 - for the practical purpose of discovering whether alleviation of the condition is possible. It is probable that the most serious effects will be found to be upon the motor control and attention - the latter being an important matter, affecting the whole range of efficiency. The effects on the zeal, trust- worthiness and fidelity, although of highest importance, may be expected to be very difficult of determination. The determination of visual effieiency with different types of mask, is exceedingly important. The limitation of total range of vision by the mask is important in itself, and also has a bearing on the mental and physical discomfort and irritability. Of at least equal importance is the restriction of the field of binocular vision: the field necessary for accurate perception of distance and topographical relief. After everything possible has been done to adapt the mask to the soldier, there still remains the problem of adapt- ing the soldier to the mask* A continuous study of the problem of bringing the soldier to acceptance of the necessary limita- tions of the mask, enduring it with the least mental and emotional resistance, and being practically faithful to its use, is very desirable if the maximal effioiency is to be ob- tained from these appliances. With the above remarks, which are oertinent to the question of gas mask design and the physiology of wearing the gas mask, we will take xvo the factors indicated in the first - 170 - part of this report: namely, dead air spaoe and resistance. DEAD AIR SPACE The percentage of carbon dioxide in the expired air is always lower than the percentage of carbon dioxide in the air remaining in contact witth the alveoli, for this expired air has passed through the dead space of the bronchioles, bronchi, trschea, etc., and has been subjected to the diluting 1 effect of the atmospheric air which occupied the dead soace at the end of the previous inspiration. It is obvious that, as ex- piration proceeds, more and more of this atmospheric air in the dead space is pushed along with the outgoing air from the lungs, and dilutes the latter. This effect decreases, so that samples of the expired air taken at intervals daring an expira- tion will show an increasing concentration of carbon dioxide, until the last portion will show the highest concentration, but a concentration lower than that in the air in the alveoli. How in any type of mask or breathing appliance there is produced the effect of increasing the size of the dead air snace and the amount of dead air, for no mask as yet designed has allowed a perfect exit for the expired air; some previous- ly expired air is always mixed with that inspired at every inspiration. Since this previously expired air in the mask is that from the end of a previous expiration, it contains a relatively large amount of carbon dioxide- In other words, at every inspiration a man wearing a mask draws a certain amount - 171 - of carbon dioxide into his lungs alone with atmospheric air. The harm of this is obvious, and it is in direct proportion to the amount of carbon dioxide rebreathed, for since the carbon dioxide content of the blood must be kept constant and the rate of carbon dioxide elimination by the lune-s must be exactly equal to the rate of carbon dioxide production by the tissues, and also since the storage capacity of the body is most limited, the minute volume of the respiration must be increased to eliminate the sum of the amour t of carbon dioxide produced in the body at that particular respiratory cycle plus the amount of carbon dioxide rebreathed from the mask. The harm of the dead space in a mask,, therefore, is proportional to the amount of carbon dioxide which it contributes to the inspired air; or, putting it in another way, to the increase in the minute volume Of air necessary to maintain a normal carbon dioxide content in the blood leaving the lune-s. It is obvious that if we know how much carbon dioxide there is between the mask and the face after a normal expira- tion and the quantity that remains in the mask after a normal inspiration, we can subtract the latter from the former and have the amount which " f as carried into the lungs during inspiration. We have performed experiments on different tynes of mask in an effort to classify them in accordance with the above The subject was required to wear the mask while resting in a chair. He was then given literature to read in order to - 172 - keep his mind free from his breathing. After he had remained perfectly quiet for eight or ten minutes, he was told to hold his breath at the instant when he stooped exhaling. While the subject was holding his breath, 2500 c*c. of atmospheric air was pumped through the mask and collected into a spirometer, this air being forced through in intermittent blasts in order to insure the complete washing out of the mask. The air col- lected in the spirometer was then analyzed for the per cent of carbon dioxide, which, when multiplied by the 2500 c.c. volume, will give us the number of c.c. of carbon dioxide contained in the mask after expiration. In a similar manner, after the subject had breathed quietly for a period of ten minutes, he was again told to hold his breath at the instant when he finished a normal inspiration. Again 2500 c.c. of atmospheric air were pumped through the mask, which completely washed the carbon dioxide out, and this air was collected in a spirometer. The difference in the number of c.c. of carbon dioxide obtained, after a normal expiration and that collected after a normal inspiration will give us the amount which was carried into the lungs during every inspiration An average of sixteen determinations on eight individuals for each type of mask gave us the following results: GEER MASK - 6 c.c. C0 2 taken into the lungs (Experimental Mask) with each expiration A,T. MASK - 11.2 (Production Mask) K.T. MASK - 16.8 (Production Mask) - 173 - How let us see what this win mean in regard to wasteful ventilation, let us assume an average expiration to be 500 c.o. with an average carbon dioxide content of 4% which will mean that 20 cc of carbon dioxide are given off at each expiration. (The above figures are assumed to be a very close average for a man at rest) . If the subject was required to insoire 6 c.c. of carbon dioxide, as is the case with the Geer Mask, then in order to maintain the carbon dioxide content of his blood constant it will be necessary for him to expire SO c.c. of carbon dioxide, which is produced during the respiratory cycle, plus the 6 c.c. inspired from the mask, or a total of 26 c.c. of carbon dioxide would be sriven off at each exoiration (6 of which were collected in the mask, and 20 of which were driven through the mask into the atmospheric air). If this man had an average expiration of 500 c.c. without the mask, he would how have 500 x 26/20, or 650 c.c, as an average expiration, or he would have 650- 550 = 150 c.c wasted breathed air at each respiration. With the A.T. mask he would have 20 c.c -I- 11.2 c.c or SI. 2 c.c of carbon dioxide given off with each expiration. Then 500 x 31.2/20 would give 780 c.c as an average expiration. and 780 - 500 would give 280 c.c of wasted breathed air while wearing the A.T. mask. With the Z. T. mask the carbon dioxide given off with each expiration will be 20 cc -+- 16.6 or 36,8 c.c Then - 174 - 500 x 56.8/20 will give 920 c.c, as an average exoiration and 920-500 would equal 420 ce, of wasted air while breathing through the K. T. mask. The following experiments were devised to test out the actual effect which the dead air space has on the res- piratory phenomena of the body* The subject was required to breathe through valves which separated the inspired from the expired air. The valves had a resistance of less than 5 mm. of water at his normal breathing rate, and a dead space of about 20 c.c. The expired air was collected in a Tissot spirometer accurately calibrated and compensated. The total number of respirations, the time, and the total volume were recorded on a smoked paper, and the volume of each respiration was figured. The subject was with- out breakfast. From analysis of the expired air, the oxygen consumption per minute, the percentage of carbon dioxide in the exoired air, and the respiratory quotient (i.e., the relationship existing between the volume of carbon dioxide excreted by the body and the amount of oxygen absorbed) were determined. The oxygen consumption and the respiratory quotient were de- termined in all cases in order to be sure that the results obtained were comparable to each other. This precaution seems to the authors to be absolutely necessary for exact work on either trained or untrained subjects. Unless experiments are so controlled, one cannot be sure that it is right to compare - 175 - results seemingly similar. The subject breathed directly into the valves them- selves, and then successively through £lass tubes of 15 mm. bore of a capacity of 187, 860 and 360 c.c respectively, at rest, walking four miles per hour on a movable sidewalk, and running 5.6 miles per hour on the same machine. The time of the experiment was determined by the length of time which was required to expire 50 liters of air, after a preliminary period in which the respiratory volume was found to be constant. A curve was plotted, the abscissae of which represented the capacity of the dead air space of the tubes, and the oriinates the minute volume of the respiration. The effect of the Goodrich-Tissot, the Kops and the Connell masks, on the respira- tion was tested under the same conditions, using the same type of valve, so that the question about the resistance of the mask was not considered, and the results obtained were inserted in the proper places on the curve. The oxygen consumption and the respiratory quotient in all the data used - and, for that matter, in all collected savs in three or four individual ob- servations which "vere rejected - checked sufficiently well to allow a comparison of the results with each other. Our results showed the effect of increasing *he capacity of the dead air space in a condition of rest or during moderate or strenuous exercise is to increase the minute volume of the respiration, decrease the percentage of carbon dioxide in the expired air, and increase the carbon dioxiie in the alveolar - 176 - air in a manner which bears a constant relationship to the dead space which is added. The effect on the minute volume of a man who is wearing the A.T. mask approximates the effect produced on the minute volume of the man breathing through a tube having a capacity of 125 c.c« The effect of the K.T. mask in increasing the minute volume "'as similar to the effect on a man breathing through a tube having a capacity of 225 e.c. The Connell mask may be compared to a tube having a capacity of 275 c.c. The actual increase in the minute volume of air observed when wearing the mask can not be interpreted as being the full in- crease "'hich would be obtained if the resistance to breathing through the mask and its tubes was a constant factor- Resist- ance to inspiration always tends to re luce the minute volume of air respired. Resistance to breathing through any of the masks is greater than that of the tubular mechanism used in the experiments. That we were able to show that the minute volume is increased in spite of the fact that the resistance of the masks tends to produce an opposite effect shows that the dead space has an effect which far overshadows the con- trary effect of the resistance of the masks and tubes. The Ha rm of the Dea d A ir Space 1. Interpretation from the physiological standpoint. (a) A larger minute volume of air is required when breathing through dead air space. This interpreted on physio- logical grounds means that the carbon dioxiie content of the - 177 - 9rterial blood Is higher than normal. The level to which the content of carbon dioxide in the arterial blood may rise is limited. Anything which wastefully increases the carbon dioxide level of the Dlood decreases the reserve so necessary to a soldier when he is asked to respond to the demand for exercise which is a part of his daily life. (b) A larger minute volume of air must be t>ulled through the canister, which offers resistance proportional to the volume of air passing through it. If resistance is a factor of harm, dead air space increases that harm, since dead air ST)ace increases the volume of air passing through the eanister. (c) As will be noted below, the effect of resistance is to decrease the. minute volume of air breathed. Dead air space increases the minute volume. Accordingly, if breathing is accomplished against resistance and through a large volume of dead air space, the volume of air breathed is reduced more in proportion to the actual needs of the body than it is when breathing against resistance is accomplished without the addi- tional factor of dead space; this, again, causes the level of carbon dioxide in the blood and tissues to be raised to a high- er level than normal, and thus again there is some reserve power wasted. 2. Interpretation from the standpoint of the canister, The life of the canister depends on the volume of the gas-laden air passed through it. The dead space increases the minute volume of air passed through the canister and, therefore, shortens its life. - 178 - EFFECT 03* RESISTANCE TO BREATHING 5eneral_consi derations . - under normal conditions the air is drawn into, the lungs by the respiratory effort with very little negative pressure (reduced or suction pressure}, The whole anatomic design of the air passages is constructed apparently with a view to decreasing the resistance to the passage of air. Probably the negative pressure exerted by the thorax to expand the lungs under normal conditions rarely ex- ceeds 1 to 2 inches of water < The addition to the human breathing apparatus of a mask, together with a canister through which the air must be pulled, at once introduces a new aspect to respiratory physiology. This factor is of special importance in the present war, in which a mask must be worn for a continued period of time, and the question as to whether or not the resistance to breathing whioh is offered by the mask and canister should be as high as is necessary to afford maximum and prolonged protection, Or this resistance should be lower on account of the deleter- ious influence which breathing against such a resistance pro- duces - is one which must be decided by experimentation. There are several considerations which can be discussed on general principles. 1 . The effect on the blo oi pr essure of increasing the inspiratory negative pressure . - The changes of pressure in the thorax due to inspiration and expiration have an appre- ciable effect on the blood pressure; and likewise the filling - 179 - of the right side of the heart is affected, owing to the fact that suction action of the thorax brings a larger quantity of blood into the lungs during inspiration. This increased volume of blood, being pushed down into the left side of the heart during the early part of inspiration and last part of exoiration, increases the mass movement of blood and tends to increase the pressure of blood. We may therefore be assured that, if the resistance to inspiration is increased, the oseillation in blood pressure due to the respiratory movements is increased. f2) The effect of negative (suction) pressure on the side o f the heart . - The blood pressure in the pulmonary arteries rarely exceeds 50 mm. Hg, which is equal to about 20 inches of water. The right ventricle and auricles of the heart are thin-walled, and will undoubtedly react to slight changes in pressure, If breathing is accomplished against inspiratory resistance, the negative pressure developed in the thorax is opposed to the pressure developed in the chambers of the heart. Accordingly, if the same volume of blood is to be maintained during the inspiratory portion of the respiratory cycle while breathing against resistance, the chambers of the heart must exert a pressure equal to what they ought to exert plus the additional negative pressure. This additional nega- tive pressure has little effect on the left heart, where the pressure is habitually high; besides, the walls of the left heart are thick and accustomed to high pressure. In the esse - 180 - of the right heart and auricles, however, when the resistance to inspiration is great, the additional load may have a marked effect, as was shown by Dr. c.P. Hoover twenty years a*?o in some experiments which he did on the changes in the second sound of the heart, v-hen inspiratory efforts were made with a closed glottis. He found that there was always a split in the second sound, and interpreted this as meaning that there was a ielay in the contraction of the right ventricle owing to the increased work which it had to do to overcome the nega- tive pressure of the thorax. We know that the right side of the heart, as compared with the left side, is not built to stand severe strain, and training in wearing masks in which the resistance to inspiration is great should be conducted with care lest the right side of the heart of the soldier be damage!. (3) The effect of inspiratory resistance on the blood and lymph content of the lung . - Dry cupoing is a recognized medical procedure. It consists in placing a cup over a portion of the body and withdrawing air from the cup, thus creating a partial vacuum in the cup. This causes an increased flow of blood into the area covered, as is manifested by redness of the skin. If maintained for any length of time, you get an exudation of lymph or tissue fluid from the blood, and minute hemorrhages, and you have produced a swelling. It seems to the authors that a similar condition obtains when breathing is accomplished against a high inspiratory resistance, for we have a negative or suction pressure produced in the -, 161 - chest, as is seen in the dry cupping. The physiological effect which such an increase in long-tissue volume produces can conceivably lie in altering the facility ^ith which oxygen can enter the blood through the respiratory membrane. The importance of this point is all the more apparent when we consider that respiratory physiologists are split into two schools. One school believes that the absorption of oxy- gen from the blood by the lung air is purely under physical laws, assuming that the difference in the pressure of oxygen in the lung air and that in the venous blood is sufficient to account for complete saturation of the blood in the lung with oxygen. The other school believes that the pressure differences existing between the lung air and the arterial blood, especially during extreme exercise and at high alti- tudes, is not sufficient to account for the phenomenon of oxygen absorption; therefore they believe that the respira- tory membrane of the alveoli acts as a secreting gland, secreting oxygen from the lung air into the blood, as it were. The reason these two schools exist is that the methods of analysis of the situation are not exact enough to determine which side is right or wrong. Apparently the limits of error of the methods of investigation lie outside the critical point of decision. Any factor which changes the thickness of the respira- tory membrane will interfere with the gaseous exchange by the alveolar air and the blood, and this change in thickness of - 182 - the respiratory membrane can probably be brought about by the suction produced by breathing against a high resistance. Experimental considerations . - (1) The effect of resistance on minute volume of air breathed .- Date- collected in this laboratory and in the Philadelphia and Mew York Gas Besearch laboratories have shown conclusively that there is a marked decrease in the minute volume from the normal when there is any resistance. This decrease in the minute volume of air breathed of course demands an increased percentage of carbon dioxide in the expired air, since a less amount of air must be respired for excreting an eqptal amount of carbon diox- ide. This being the case, we must assume that the blood leav- ing the lungs contains a higher percentage of carbon dioxide than it ordinarily does. The body can compensate for this in two ways; (1) by increasing the amount of carbon dioxide in the tissues and blood, equilibrium being established at a high- er level of carbon dioxide pressure; or by (2) increasing the mass movement of blood to mainttn the normal level of carbon dioxide and oxygen concentration in the tissues. If the former holds good, we are seriously affecting the well-being of the tissues. If the latter holds good, ™e are reducing the re- serve efficiency of a man's heart, which is the weakest of the factors controlling a man's ability to do hard and sudden work. If the bloodflow is not increased and carbon dioxide accumu- lates in the tissues, we have good reason to believe that oxidation is immediately and seriously interfered with, ana - 183 ■■ there will result an accumulation not only of carbon dioxide but of other waste products which are harmful to a degree more than the carbon dioxide itself, and which in the normal course of events would have been further oxidized to rela- tively harmless, easily excreted substances. (2) Importance o f resistance t o leaks in the mask during inspir ation . - Since the w'ar Department has definitely given its approval to the Tissot type of mask in preference to the mask in which breathing was accomplished through the mouth with the nose stopped, as with the English box respira- tory, the importance of air entering the mask by routes other than through the canister has become 9cute. The test of the tightness of fit of a gas mask has hitherto been whether or not the mask protected the wearer when standing in an atmos- phere of ga3, as determined by the subject. This is good as far as it goes. Under conditions of exercise, however, when a larger minute volume of air under a greater suction pressure is drawn into the mask, small leaks which may not be evident under the conditions of rest will develop. A specially constructed apparatus has been devised in this laboratory to determine the amount of leak in a mask under varying degrees of pressure. The K.T- mask allows more air to leak into the face than does the A. T. mask on the average but apparently it gives ample protection while the soldier is at rest, in spite of the fact that many masks allow the en- trance of between 600 and 1300 c.c. of air with a 2* inch - 184 - suction pressure. But while it is quite true that the masks which show a large leak-in at a moderate pressure may give ample protection to the soldier while at Eest, we have not conclusive proof that these masks will protect when the minute volume of air is increased, as. during hard muscular work. From the fact that there is a considerable leak-in under low suction pressures in the Tissot type of mask, it is obvious that the resistance of the canister must be kept below that point which will permit a large volume of air to leak into the mask by other routes than the canister luring muscular exertion. In other words,, there must be a correla- tion between the resistance of the canister and the volume of air which leaks into the mask in other ways than through the canister. In the past the canister has been produced with absolute disregard of the man making the mask. The, effect of canister resistance on the rate of air entering the lungs and on the lengths of t he i nsni rato ry and expiratory periods of the respiratory c ycle . ( prov isi onal Report). - When a man is breathing, while at rest, through a canister having a 2 inch resistance, the inhalation time is about 35<$, exhalation is 43$. and the rest period is 2?A of the respiratory cycle. With a six inch resistance the in- halation period is 39$, exhalation 45$, and the rest period is 16$ of the total cycle. It will be noted that the length of the inspiration period is somewhat lengthened, and the rest - 185 - period is reduced. The exhalation period is not affected to any great extent. While walking and breathing through a 2 inch canister, inhalation is 44$, exhalation 42$, and the rest period 14$ of the total cycle. When breathing against a 6 inch resist- ance the inspiration is 48$, the exhalation 39$, and the rest period 13$ of the total cycle. It will be noted that the inspiratory period is considerably lengthened both at the expense of the rest and the expiratory. When running and breathing against a 6 inch resistance the maximum rate of air entering the lungs is 132 liters per minute, when a man is breathing at a rate of about 40 liters per minute. ($ote that this is the maximum flow and not the average rate volume flow during inspiration, as is given in the above cases). In this case, however, the inspiratory period is increased, so that the average rate of entrance of air into the lungs is probably not over 60 liters per minute, while that of expiration is not over 120 liters per minute. Even at maximum rates of expiration the volume rate cannot be over 200 liters per minute, and probably never goes over 150 liters. - 186 - APPENDIX xJ REPORT OK FI3LL T^ST OF THd GOODHICH-LAKSdILJ MASKS lviajor R. G. Pearce The armistice prevented any intensive work being done on the further development of the Goodrich-Lake side Mask. It is necessary to determine many r>oints about a mask by actual work in the field on a large number of men. Such tests on the Goodrich-Lakeside mesk were imoossible save in the most limited and most unsatisfactory way. The original model of the mask was tested along physio- logical lines at the Lakeside and the Goodrich Laboratories and was found to approach more closely the physiological specifications of an ideal mask than other masks tested. A man can see more, run furthor , and do sustained work longer ?n this mask than in the standard mask, the Akron Tissot, or the Kop-konroe mask. This was expected because the mask conformed to the physiological requirements of the respiration and vision more closely than do the others. About twenty (20) of these masks were made up in two sizes (size 3 and 4 approximately) and were taken to the American University, Washington, D.C. on November 22nd for a (187) preliminary test. The #4- mask was found unsuitable, because its dimensions were not correlated. Altogether thirteen (13) men were fitted with #3 mask and carrier. The masks were all tight in gas chamber; the cap for the most part was too small; there was some discomfort under the chin and about the left eye', the tyne of deflector was not satisfactory. The carrier was not altogether successful; first, there was too much cloth in the vest; and, secondly, it was not a universal fit. The gei^aral opinion of the men, who were all old field-testing men, was that the mask was far superior in general principles to any that they had theretofore worn; they all agreed that its vision was the best and that the amount of exercise which it allowed them to undergo was greater than in the other tyoes of masks tested. Because the obvious defects of the mask were easily remedied a more extensive test was not made at that time. Kajor Fogler, of the Research Division, very kindly gave us the help of kr. xilton W. killer to aid us in the design of a new harness for the carrier and in making changes in the mask. Although it was quite impossible to do extensive devel- opment work at that time because of the armistice, there was a serious attempt made to increase the efficiency of the harness and to make the mask fit better. To this end a simplified harness was made which consisted of straps about the body, to which was attached a w»v Q carrying the canister and mask. This simplified harness proved to be practically an universal fit (188) and to be much more comfortable than the semi-vest design originally used. At the suggestion of one of the men in the field-testing squad it was found possible to swing the mask pocket from the breast position to the rear of the left arm to which it was attached by a band encircling the arm, An attempt was made to make #4 mask fit better and to increase the size of the horizontal band dimension in the #3 mask. The edge of the mask passing about the chin was made into a rolled edge, and more attention was tsaid to the deflector. About twenty (20) of these masks and carriers were made up and taken to the American University on December 17th, 1918, where they were given a short field test by Lieut. Jordy. It was found that the alterations made in the horizontal band of the #3 mask had made it less effective in forming a tight seal across the forehead than did the original aesign. It was found that the deflector was not suitable and gave too high a resistance. The carrier was found to be eminently satis- factory and met with the approval of all the men in the test. The mask likewise met with general arvoroval, the men all s /ing that it had features far superior to any existing mask. The results of this test were so gratifying that it was thought best to have a larger field test made at Long Island by the Gas Defense testing squad. Although the mask had many obvious defects such as want of ruggedonss, a somewhat unsatisfactory deflector, an incom- pletely developed band about the forehead, and, what was more {189) important, the mask was limited to practically one size; this size being somewhat larger than the ordinary fr$ mask. Thirty- eight (58) of these mp^ks were taken to the Long Island plant and a test made, whicn «»ras in charge of Gantain koulton. The test was unsatisfactory in many ways, many of the men employed were not accustomed to making mask tests; they did their work in an absolutely disinterested manner, some of them making the statement to my sergeant that they did not give a hang what they said just so they would get through with the d job. Coincident with the test on the Goodrich-Lakeside mask tests were made on the new Koxj-konroe mask. Twenty-five (25) men were assigned to each of the squads. In spite of the marked, yet pardonable, lack of interest on the nart of the men em- ployed in the test and their lack of experience in wearing the Goodrich-Lakeside mask and a strong prejudice expressed to my sergeant, in favor of a mask and carrier to which many were accustomed, the test was instructive. The Goodrich-Lakeside mask (that is the mask considered entirely apart from the carrier) met with iDractically unit sal praise in those t>oint£ in which the mask really attempted to be strong; i.e. its physiological adaption to body needs. Failure to have a number of assorted sizes led to some leakage in the gas house and discomfort, 'Jfee mask was not rugged and was criticized on this point. The men saia the vision was good; that it was very comfortable, and, in a careful canvas of the men who were accustomed to making mask tests, I deter- mined that they were practically unanimous in saying that the mask was superior in the manner of allowing freedom and ease of work to the other masks which they had tested. On the other hand their opinion of the carrier was practically unanimous disapproval; this was due to two reasons fl) the apparently complicated harness which they were unaccustomed to wearing; and (2) to the fact that the carrier, as it is now designed r does not remain in place and does not prevent the very heavy 1919 canister from jolting on the oack. Prac- tically all the men complained of the tube going to tbe left shoulder, expressing the fear that the tube would be injured when anything was carrier on the left shoulder. That the carrier was unsatisfactory as now designed was apparent, and steps should be taken to remedy its obvious defects. In my mind there was no evidence produced by the test that the posi- tion of the carrier was not superior to the front position. In the gas house a surprisingly large number of Goodrich- Lakeside masks leaked; a great deal of this fault was due to an improper fit of the masks - a greater number of sizes of this mask should be de-el oned. The mask when it fits has '. en shown to be more gas tight t han any o ther mas k- The mask should be more rugged; made in a number of sizes; more devel- opment work should be done on the manner of lacing the cap, the kind of fabric to ase in the cap, or even whether any fab- ric is necessary; the band oassing about the forehead should be modified a little so that it would not mucker; the deflector is not altogether satisfactory, and work should be done in (191) developing a better t,ype of deflector; the manner of attaching the entire tube by a loop to the side of the mask is not al- together satisfactory, The good points of the mask which the test showed were- 1. Its -^reat range of vision 2. Its low exhale resistance S. It s comfort 4. Its ease of adjustment 5« Its freedom from dimming The test failed to show that a single principle involved in the mask was incorrect; it did show that some of the mechanical features of the mask should be improved. Inasmuch as the mask was presented NOT as a finished product and ready for immediate practical use, but rather as a mask which attempted to illus- trate certain important physiological and mechanical principles of mask design, we believe that any criticism of the mask which does not carefully distinguish between the principles of mask design involved and the actual mechanical featixres of the mask in comparison to othei 3xisting masks is unjust* The Soodrich- Lakeside mas& and carrier as it stands undoubtedly needs development, especially in the matter of minor changes of design, material and manufacture* Were these changes made, undoubtedly, much of the adverse criticism of the mask and. carrier would be met. To my mind the test did show one thing conclusively; that is, if masks are to be used in the future they should be improved along the lines which the Goodrich - Lakeside mask attempted to follow out. tfith increase in the (199 ability of the canister to take care of gases and smokes it should be "oossible to place the canister on the mask itself and thus do away with the heavy canister and carrier. i/ve wish to thank the Gas Defense Division and especially Captain mouiton for his interest in conducting the test at Long Island. we wish to especially thank tne Research Divi- sion and Major E'ogler and Mr. killer individually for their help in design and testing. (193 INDEX Air : Lungs, composition of ieo Minimum volume required for work 55 Minute volume ^59 - - for work 57 , resistance, effect of 63,65 Physiological requirements for normal respiration '55 Air flow: Resistance of valve, relation to 133 Akron Tissot Mask: Analysis of 40 Dead air space 173 Pace piece, chlorpicrin, absorption of 97,100 Het dead air space 74 Range of vision 81 Resistance to inhalation 123 Artery: Temporal, blood flow in, effect of mask on 84 Blood: Circulation of, respiration, relation to 165 Minute volume, oxygen consumption, relation to 167 Blood flow; Temporal artery, mask, effect of 84 Blood pressure: Resistance to breathing, effect of 60,179 Breathing: Canister resistance, effect of 185 Resistance to, effect of 60,179 Breathing requirements: Gas mask 12 Goodr ich-lakeside mask 48 Canister : Dead air space, relation to 178 Mask, relation to 16 Resistance, effect on breathing 185 Carbon dioxide: Alveolar air, percentage in 163 Excretion and oxygen consumption 158 Carrier: Akron Tissot Mask Ad Goodrich lakeside mask 51 Position ^1 Specificatibns 31 Chlorpiorin: Absorption by face pieces 94 X46 Estimation, physiological " ' 101 Eye, calibration of 101 leakage in mask under reduced pressure 92 Rubber, absorption by 98 104 147 Comfort; * ' Goodrich lakeside mask 50 Connell Mask: Analysis 4.7 "Cure" Valves, effect on 144 Dead air: Composition 161 Dead space : Akron Tissot mask 41 Canister, relation to 178 Definition 15 t 161 Determination by lakeside-Lewis method 71 Goodrich-Iakeside mask 49 Harmful effects 75. 177 Eops Tissot Mask ' 46 Masks 171 .Minute volume of air, effect on 69 Net. of various masks 73 Objections to 15 Respiration, effect on 175 Exercise : leeksFe, effect on 117 Exhalation: Resistance to, of Akron Tissot Mask 40 Maximum rate 65 Exhalation valve : Comparative study 126 Construction 29 Opening pressure 133 Resistance of 128 - , air flow, relation of 133 - , thickness of stock, relation of 137 Expiration: Canister, resistance, effect of I-r Inspiration, relative time of .164 Resistance to, in mask 14 •Eye-: Chlorpicrin, calibration to 101 Eye piece : Construction 30 Face • Mask, pressure of l^g Face band: Mask 22 Face piece; Chlorpicrin, absorption of 94,146 Phosgene, absorption of '94 Flutter valve : Goodrich valve, comparison of 126 Gas mask: See Mask Gas tightness: Mask, determination of 86 Geer mask: Dead space 74 t j.75 Glycerol: Valve leakage, effect on 77 Goodrich-Lakeside mask c Analysis 47 Description 2 Historical 1 Net dead space 74 Resistance to inhalation 123 Goodrich valve : Flutter valve, comparison with 126 Testing machine 151 Harness; Mask 22 - , determination of maximum tension of 88 - , forces, exerted by 89 position, leakage, effect on 114 - , tension, effect on 114 Head band: Adjustment 22 Akron Tissot mask 42 Design 22 Head harness: See Mask, and Harness Head measurement: Comparison of 11° Heart : Right side, resistance to breathing, effect of 60 Heat; Valve leakage, effect on 77 Hull method: Maximum tension exerted by mask harness 88 58 26 Inhalation; Maximum rate cc Resistance of masks to 123 Resistance to, respiratory circle, effect on Inhalation tube : Clarity of vision, relation to Design 25 Inspiration: Canister resistance, effect of 165 Expiration, relative time of 164 Resistance to, of Akron Tissot Mask 40 Zops Monroe Mask; Analysis 46 Zops Tissot Mask: Analysis 45 Dead space 173 ?ace piece, chlorpicrin, absorption of 96 Net dead space 74 Range of vision 81 Resistance to inhalation 123 Laohrymation: ?actors of, when "'earing mask 93 lakeside-Goodrich method: Gas tightness of mask 86 Pressure exerted by bands of mask 82 Range of vision 81 lakeside Lewis method; Dead space 71 Leakage: Akron Tissot mask 40 Chlorpicrin, under reduced pressure , 92 Exercise, effect of 117 Mask, Pearce-York apparatus for 108 - , resistance to breathing, effect of ig4 Pearce-York and gas chamber tests, comparison of 92 Protection, relation to 24 Valve, under various conditions 138 lung: Blood content, resistance to breathing, effect of 62,181 lymph: resistance to breathing, effect of 62 Mask: Analysis of 39 Bloodflow in temporal artery, effect on 84 Breathing requirements 12 Canister, relation to 16 Comfort of 18 Face, pressure on }j2 Fighting Specifications 4 Gas tight face fit 21 Gas tightness, determination of 86 Harness 22 , determination of maximum tension of 88 , effect of position on leakage 114 , effect of position on tension 114 , forces exerted by 89 , pressure exerted by measurement of 82 Head harness, pressure, measurement of 82 , sizes needed 36 Ideal, conditions for 37 Inhalation resistance 123 Leakage, determination of 86 , Pearce-York apparatus for 108 , Pearce-York and gas chamber tests compared 92 leakage and protection 24 , resistance to breathing, effect of 184 Material of construction 21 Number of sizes 111 Physiological factors 155 Physiological specification 12 Primary specification 12 Production 35 Psychology 169 Rating chart 153 Resistance to expiration 14 E,?.E. 10 Mechanical specifications A. T. Mask 42 Goodrich Lakeside Mask 50 Mask 20 Minute volume 159 Air, dead space, effect of 69 Air, required for "'ork ^ 57 Air, resistance, effect of 63,65 See also: Akron Tissot Mask Connell Mask Geer Mask Goodrich-Lakeside Mask Kops Monroe Mask Zops Tissot Mask Oxygen: Consumption and C0 2 excretion i0 ° Consumption, relation to minute volume of blood 167 Pearce-York apparatus: leakage of gas masks 108 Phosgene : Absorption by faoe pieces 94 Rubber, absorption by 104 Protection: leakage, relation to S4 Psychology: •Mask 169 Eating Chart: Gas mask 153 Resistance: Corrugated tubing 150 Exhalation valves 126 Goodrich tubing 150 Mask, to expiration 14 Hasks to inhalation 123 Minute volume of air respired, effect of 63. 65 Respiration: Air, physiological requirements of 55 Blood circulation, relation to 165 Dead space, effeot of 175 Normal rate 158 Physiological factors 158 Resistance, effect of 63 Respiratory Circle; Resistance to inhalation, effect of 58 Rubber : Chlorpicrin, absorption of 98,104, 147 Phosgene, absorption of 104 saliva: Valve leakage, effect on 78 Temperature: Valves, effect on 148 Tube: Requirements ° 4 Tubing : "50 50 Corrugated, resistance of Goodrich, resistance of n n Valve leakage; flutter valve 7 ° Glycerol, effect of y Goodrich lakeside valve "J~ Heat, effect of 77 Valves : "Cure", effect of 144 Durability 140 Exhalation Resistance of 128 Exhalation, study of 126 Flutter, leakage 76 Goodrich Lakeside, leakage 76 Leakage 138 Rating 145 Resistance Man test of 128 Mechanical test 131 Temperature, effect of 142 Ventilation efficiency: Masks 73 Vision: A.T. Mask 41 Clarity of 18 Clarity of, relationship of inhalation tubes 26 Goodrich Lakeside Mask 49 Mask, relation of 17 Range of 17, 80 VJater : Chlorpicrin absorption by rubber, effect on 149 '