SIMULATOP REASUREBEMT OF
THE RORK OF BRIiAPHING
FOB UNDEEWATER BREATHING APPARATUS
Durcan Moir fliln~
E. Sc. Mar ire Science Stockton stat^ Colfege, New Jers~y,1973
A THESIS SUBEITTED IN PARTIAL PULPILLEEBT OF
THE PEQUIREHENTS FOR THE DEGREE OF
MASTER OF SCIENCE (KfNES IOLOGY)
in the Department of Kicesiology
a GUNCAN ROIB BILNE 1977 SIBOH FRASER UNIVERSITY
December, 1977
All rights reserved, This thesis may nct t>f reproduced
in whole or ir part, by photocopy or cthor means, without permission of tho author. NAYE: Duncan noir flllni
TITLE OF THESIS: Hespiration Simulator' Htlasur+m~n* , of the Wark of Bre3thi11y far
Und2rwater Breathinq A ppara tus
EXhnINING COMnITTEE:
Chairman: Dr. E. W. R;inister
'DL. J. n. aorrison Senior Sup:.r visor
Dr, T, W. ialv.?rt
Dr. A. E. Zhaprssry Ext +rnal Examin~r Prof -.ssor SLlncn Praser IJniv~rsity - at A,,,,,.,: ...... Jet, , V7r PART lAL COPYR lGHT L lCENSE
I hereby grant to Simon Fraser University the right to lend my thesis, project or extended essay (the title of which is shown below) to users of the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users. I further agree that permission for multiple copying of this work for scholarly purposes may be granted by me or the Dean of Graduate Studies. It is understood that copying or publication of this work for financial gain shall not be allowed without my written permission.
Title of Thesis/Project/Extended Essay Simulator Measurement of the Work of Breathing
for Underwater Breathing Apparatus
Author: (signature)
Duncan Moir Milne
(name)
17 January 1978
(date) iii
ABSTRACT
In the design of diving equipmsnt, one of the most important considerations is the underwater br+athing apparatus, The need tor rovision of the existing operating standards of breathing resistants for this apparatus is a topic ucder current discussion. Oce suggest&, but not establishea standard for respiratory devicts recommended that the r3tio between work of ~reathingior the apparatus
(kg. m,/min. ) ar,d minute volume {liters/min. f should riot exceed one-eighth.
Haasurement of the work of breathing for underwatzr breathing apparatus using a respiration simulator pzrrctits evaluation of apparatus performanct in teras of physiologically acceptable respiratory uork rates. T~P purpose of such measurement is to esta~lishrevised limits for the work of breathing and consequent increase in diver comfort, performance, and safety in underwater operations.
The ventilatcry power requirements of two opsr, circuit demand underwater breathinq apparatus Mere calculat2d usinq steady state flow aeasurements and dynamic respiratory simulations at 1 atmosphere. In calculatinq the uork of breathing, flow rates were sinusoidal and in the physiologLca1 range of up to 3 lit~rstidai volume and
30 cycles/min. respiratory frequency. Dymmic resistive work of breathing attained values as high 3s 18.56 kq.m./[nin. at 95.9 fiters/min. ventilation for a inouth-held demand regulator, A .back-mounted demand regulator attained values as high as 20.22 kg. m./min. at 80.1 litars/min. dynamic ventilation.
Approximations of the steady-state work of breathing consistently underestimated the ventilatory raquiramznts of the breathing apparatus, apparently as a result of hyster5sis losses and exhaust bubble formation in the apparatus.
Steady-state flow testing was thus found invalid as a weans of evaluating the work of breathing in underwater breathing apparatus.
The diffsrence in hydrostatic pressure betwean +hz div9rqs lung csctroid and the demand regulator diaphragm of his open circuit breathing zquipment (i,e., the ambi~nt respiratory pressure) was also rssasured for ten divers.
This was done at several swimming orizctations and in a working positicn usicg both mouth-held and back-mounted demand regulators. flean values of hydrostatic pressure in swimming were fcund to be of thz form 40.0 sin (a-14.5 ) + 4.3 cm. H 0 with a mouth-held regulator and 27.9 sin(a+33.8 )
+ 2.9 cm. H 0 with a back-mounted rsgulator, wnars "3" rzpresents the orientation of the diver with respect to the horizontal, (-90. 24.1 + 3.7 ca. H 0 with a mouth-held reguldtor and 24.7 + 2.6 cm. H 0 with a back-nountsd regulafor, . This data was used to determine the effect of hydrostatic pressure imbalance or, the inspiratory and expiratory coinpmFnts of the total work of breathing. Results indicatz that in the worst cases, hydrostatic pressure imbalance may cause a two to four fold increase in inspiratory or expiratory work. Ths results of this study support those of cthsr investigations, that even at 1 atmosphere some underwater breathing apparatus presently in use exceed recommended respiratory power requirements at ventilatory ra t$s associated with heavy axsrclse, Appreciation is extended to Dr. J. 8. Morrison, Senior Supervisor, for his advice acd support during the course of this study. Chris Dewhurst and Jerry Barenholtz provided the Analog/Digital Programmir,g, Thanks also go to the subjfc ts who volunteered their participati~nin the hydrostatic pressurz i~balanceinvestigation. vii Approval pq. ii Abstract iii Table of Contsnts vii List or Figures viii List o t Append'~XSS xii Introduction 1 delltkd Li tt-rature Part I. Recent Diving Practice ?art 11, Pactors in Diver Zespirdtior~ A. Work of Breathing b, Physical Work Load C, Gas Density D. External Resistance E. Additiondl Pactors ?art 111. Breathing Apparatus Evaluation A. Sourc~sof Bechanical aesistance B. T~stingand Standards Hethoas G Apparatus part i. fiesistlvt Work/Static Tests 29 rart 11. Resistive Work/Dynamic Pests 32 Part 111, Hydrostatic dork Detarininatlori 4 1 Part I. Resistive Work/S tatic Tzsts 45 Part 11. Resistive Work/Dyuaaic rests 55 Part 111. iiydrostat~cHark Deterlaination 75 Discussior 8 1 A ppenaixes 104 viii Figure 1 Ventilaticn, {liters/min.) , as a function of tidal volume, (liters). at 1 and 4 ATA breathing air. From Holtagrfn, et.al., (1973), and Eorrisoc, et.al., (1976.) Figure 2 U.S. Navy MIL-R-24169A (SHIPS) underwater breathing apparatus acceptance criteria. Peak inspiratory and expiratory resistance, (lam H20), as a function of depth, [FSW.) Figure 3 Side view of respiration simuiator and associated apparatus. Figure 4 End view of respiration siinulator showiog drive train. Figure 5 Subject DM in a swimming orientation for hydrostatic pressure imbalance test using mouth-h~ld regulator. Chest, tank, and horizontal reference markers are visible. Pigure 6 Subject DH in a vertical working posltion for hydrostatic pressure imbalance test using back-mount;d regulator. Chest, tank, and horizontal reference markers are visible. Figure 7 Poseidon dry static inspiratory resistance, (mea H20), as a fuuction of ventilation, (liters/min.) Figure 8 Poseidon dry static expiratory r~sistance, (naea H20), as a fuiiction of ventilation, (liters/min.) Figure 9 Poseldon wet static inspiratory resistance, (lam H20), as a function of ventilation, (liters/min.) Figure 10 Poseidon wet static expiratory resistance, (IR~Fi20), as a function of vantilation, (liters/min.) Figure 11 Trieste 11 ary static inspiratory r~sista~ce,(ma H20), as a furction of ve~tilaticc, (liters/min.) Figure 12 Trieste 11 dry static expxatory resistance, (mm H20), as a function of VEC tilation, (liters/min. ) Fijurz 13 Trieste fI vtt static inspiratcry resistance, (mm H20), as a function of ventilation, (liters/min.) Pijure 14 Trieste I1 uat static expiratory resistance, (mm H20), as a function of ventilation, (liters/min.) Figure 15 Uncorrixted ana compression correctsd piston displacement, (ca.) , for Poseidon regulator. 1 ATA v~t dynamic test at 2.0 liters tidal volume and 17.7 breaths/min. respiratory frequency. Plow, (litsrs) , as a function of tim2, (saconds) , for Poseidon regulator. 1 ATA wet dynamic tlst at 2.0 liters tidal volum~and 17.7 breaths/min. Pressure, (mm HZC), as a function of tiae, (s2corids), for Poseidon single hose regulator. 1 ATA wet dynamic test at 2.0 liters tidal volum and 17.7 breaths/min. Figure 18 Urcorrec ted and compression corrected piston displacement, (cr~.), for Trkeste 11 regulator 1 ATA wet dynamic test at 2.0 lit2rs tiaal vof ume and 20.8 breaths/m~n. respiratory frequeccy. Plow, (littrs), as a function of tine, (seconds), for Trieste 11 regulator 1 ATA wet dynamic test at 2.0 liters tidal volume and 20.8 breaths/min. respiratory frequency. Figure 20 Pressure, (am H2C), as a function of time, (szconds) , for Triests I1 two hose regulator 1 ATI vet dynamic test at 2.0 liters tidal volum2 anJ 20.8 broa ths/min. respiratory frequency, Flgure 21 Resistive work of bz*athiny, (kg. m./mir..) , as a function of v~rtilaticn, (liters/inin,) , f~r Poseidcn mouth-held opzn circuit underwater breathicg apparatus. Dynamic testing of apparatus nmaersed iri water. Haximum and reconmended standards by Cooper, (1360a), are also shown. Figure 22 Resistive work cf brsathing, 7 1 (kg, m./min.) , as a function of vectilation, (liters/min.) , for Trieste I1 back-mounted open circuit underwater br+athing apparatus. Dynamic testing of apparatus ~rnrn2rssd in water. Maximum and recommended standards by Cooper, (1950a), are also shown. Pigur.3 23 Poseidon inspiratory and expiratory 73 resistive work of breathing, (kg,rn./min.), as a function of ventilation, (1iters/min.) Dyiiamic testing of apparatus immersed in water. Figure 24 Tritste I1 inspiratory and expiratory 73 resistivt work of brzathinl~, (kg,a./min,), as a function of vefi tilation, (liters/min.) Dyuamic testing of apparatus immersed in water. Figure 25 Variation in vertical distanca bet ween 76 lung centroid and deinand valve, (cut,), as a function cf diver orientation with respect to the horizontal for mouth-held demand regulator. Figure 26 Variation in vertlcd distancz betieen 78 lung centroid arid demand valve, (cm.), as a function of divzr oriantation with respect to the horizontai for back-mounted demand regulator. Figurn 27 The icspiratory wrk psrcentaga 95 of the total wcrk of br'athinq as a function of div3r ori2ntation with r~spectto th? horizontsl. Based on 1 ATA dynamic testing of a mouth-held open circuit regulator immersed in water. Figur3 28 The Fcsplrat~rywork ptrcent3ge 8 5 of the total work of breathing as a function of diver orientati~n with respect to ths horizont31. Based on 1 ATA dynamic tssting of a hack-mounted open circuit regulator imtalrszd in water. Figure 29 Xnspiratory and expiratory work 87 expressed as a percentage of the total work of Sreathicy. The figure shows work both with and without hydrostatic imbalance. Based on 1 ATA dycanic testing of a aouth-held open circuit regulator at 75.6 littrs/min. ventilation immersed in watsr, Figure 30 Inspiratcry and expiratory w~rk 89 expressed as a percectage of th~total work of breathing. The figure shows work both with and wlthout hydr~static imbalance. Based on 1 ATA dynamic testing 3f a back-mounted ~poncircuit regulator at 80.1 litors/min. veatilaticn irom~rsedin water. xii A~p"ndix A Ccmputsr Program far 3+sistlv, Wcrk/Static Tests App3ndix B Computer Program for Resistiva Work/Uyfidmic Tzsts Appendix C ily cirostdtic Pressure I muaiance 115 Subject Data Appendix i) Steady Stat? ~stimltimsof tn-. k'ork 117 of Breatning for Single Hosd and Two Hose Regulators App.=ndLx E Poseidon Single HOSE! Dynamic riork of 120 Breathing Calculations Appecdix F Trirsae LI Twc Hosz Dyramic Vor~3f 127 braathlr,g Calculations The ability of man to not only survivs, but also to perform useful work in the ocean has becorns increasingly important to scientific, military, arid ecocomic Interasts. For the working diver, bottom tirn?, pressure, thermal-balance, mobility, and equipment all represent physi~logicalchallenges whose consideration becomes mor2 and more important as his task requirements increase, An understanding of the relationship betweec these conditions and the diver is necessary for increased undarwater work capacity. Additional inforiaation on energy expenditures of divers is needed, Ergonometric tests which reproduce real conditions must therefore be devised, (Bradley, 1973.) In the design of the man/~achine syste~,the most critical of the diver's equipment is the und3rwater bre3thing apparatus, (UBA) . At pressnt, however, the only breathing resistance standards in op4ration for UBA are U.S, Navy peak inhalation and exhalatioc pressure limits f3r open circuit scuba (Reimers, 1973) . Ths potential importance of simulator m3asureiaent of UBA resistance as done in this investigation is in providing a means for th~assessment 3f existing units on I physiological basis with possibie incorp~rationinto two long term aims: 1. Increased diver performance thr~ugh minrmization ~f the physiological cost of meeting equipment respiratory asmand. 2. Establishment of standards of aaxiiuum allowable UBA resistance. Finally, an increase in qeneral diver comfort will favorably affect the efficiency of the diver and thus have a diract bearing oc safety in underwater operations. ZELATED LITERATUitE PART I. RECENT DIVING PRACTICE Ir order to prolong a diver's stay underwater, he must 59 stlppfied with a breathable gas mixture. This can be furnished remotely froa either an underwater habitat or from the surface via hose, as with helmet diving, but this has the disadvantages of restricteii mobility and the possibility of the hose fouling on obstructions. A second method, which supplies air through personally transportea cylinders and is known as self-contained underwatar breathing apparatus, (scuba), may be one of three types. Oppr circuit scuba supplies gas through a demand valve system and all expired gas is exhausted into the water. The semi-closed circuit scuba delivers nitrogen-oxyg~n or helium-oxygen nix from the cylinders to a collapsible breathing bag. Exhafed gas p3sses through a carbon dioxide scrubbar 3nd returns to the breathing bag for reuse. A purge valve permits excess gas to escape froa the bag to prevent overpressure. The cioseir circuit unit, similar to the semi-closed circuit device, utilizes the oxygen in the breathing gas mixture without overpressure purge by weasuring the exact amount of oxygsn required for make-up. While extending dive time for a given amount ?f gas mixture, this requires reliable oxygen sensors to insure correct composition for a particular depth. PART 11. PACTOES IN DIVEB RESPIRATION aan 's functional capacity in t h? hyperbsric environment is limited by his rjspiratory system ard suppporting equipraent. The a mount of ~hysicaiuorK ~xpen~iture,the breathing gas density, nnd the mechacical r+sistance imposed by his breathing apparatus all crelte respiratory loads that the diver must be able to sustain. Inadequate lung ventilation resulting f roin the inability t:, t3lerate such increased loads leads to ~levatedalveolar C02 and thus arterial C02 distubances, (~anphiar, 1969: and Craig, et .al., 1970.) Human simulator tzsting Beasures "the critical perforrnanc~charactsristics ~f a piece of equipment Dver its entire intended operational envelop^,^ (Reirners, 1973.) UBA siiaulator testing requires detailed information on diver respiration, particularly ventilation rate, {VE) , and tidal volumo, (VT), collected under field conditisns for constructive evaluation. A. WORK OF BREATHING fha large ventilation required to ~aetthe metaboli:: d+m3nds of heavy exerciss result in a c3nsiderabl2 increase in th? work c;f breathing. The total physical work of breathing, which includes both tissue and gas flow resistance, by resting subjects at 1 ATA is approxirn3tely 0-3 kq.m./min., {HcIlroy, et,af., 1954: Otis, 1954: and Hodstrand, 1969.) The aechanisrns which control frequency and tidal volume with variations in ventilation are not completely clear, but an optiatal frequency of braathing axists for a given rats of ventilation and is sensitive to external resistances, (HcIlr3y, et.sl., 1954 E 1956: and Cr3sfill E Widdicor~be, 1961.) Otis, (19%) , suggested that frequzncy was adjusted to ninimiz~the work of breathing, while flead, (l963), put forth least average muscle force as the determininq fact3r for breathing rate. Hey, et,al,, (196~)~fourid a linear r+latiocship between VE and VT up to a VT of about half vital capacity. Further increases in VE w+re a result of increased respiratory frequency while VT r$mained constant, This "break point" variation in VT has betn reported by other invsstigators during underwater swimmi~igtrials and hyperbaric chamber tests to 4 ATA, (Bradner, 1953: and Morrison, et ,al,, 1976,) Tidal voluae, (liters), is plotted as a function of ventilation, (liters/min.), in Figure 1 from Holmgrcn, et.al., (1973): and florrison, ~t,al., (1976,) Figure 1 Ventilation, (litsrs/mi,?.), as a fucction of tidal voluma, (_Titars), at 1 and 4 ATA breathing air, From Holrngren, et.al,, (1973). and &orrison, et.al., (1976.) I HULtlGREN: 1 RTR HORRI SON: HORRI SON: TIDAL VOLUME VS. VENTILATION Elevated cnd tidal c02 acd marked slower and deeper breathing with long post-inspi ra tory pauses has been noted in trained underwater svimm2rs when compared to sedentary and athlstic non-divers, (Goff, E Bartlstt, 1957: Rorrison G Florio, 1971: and Lally, at.al., 1974.) This has been suggested as being partially the r2sult of a significantly lower oxygen v~ntilatiocsquivalent, (the ratio of ventilation to oxygen consumption), in trained subjects, {Gof f G Bartlatt, 1957.) No specific advantage has been found for interaittent negative-pressure breathing, or "skip-breat hing,If sometimes performed by divers, {Daiglo, 1975.) Physiological dead spzic~,the volume of inspiratory air ramalning unmixed in ths airways and alvmli, has be+n found during heavy exercise to ba approximately twice resting values as a result of larger tidal volumas, (Asmussen & Nielson, 1956: Hedenstiema, 1972: and sidorenko, 1972.) During maximal expiratory effort airway resistancz also increases mainly because of the collapsing of larg? airways due to elasticity, frictional pressure losses, and Bernoulli effect, (Clertlent, et.al,, 1974: and Zaaef, pt.al., 1974,) Thus, beyond a certain point flow becom~seffort-independen t and additional expiratory effort does not increase expiratory flow, [Hiller, et, al., 1971 .) The breathing co~pon+ntof undzrwater work, the vmtilatory power requirement, is coam~nlynaeasurzd in kg.m,/min. The two components of this effort result from external resistance and hydrostatic prGssure imbalance. ?. ?. "cmputer m~nitoringof tne m~chanicsof breatning, including tidal volume, respiratory frequency, and vork of breathing, has been developed by several authors to greatly facilitate the analysis of pulmonary function, {Fletcher, et.al., 1966: am3 Lewis, et.al, , 1966.) Inspiratory and expiratory phases were separated at points of zero flow. Digitized flow values were then aultipliad by corresponding dif farential pressures and the product intrejrated t:, obtain work. Re PHYSICAL HORK LOAD One of several factors affecting diver respiration, and thus UBA design considerations for breathioj gas delivery, is the amount of work exerted by th* diver. ~espiratoryrate, amplitude, and ainute volume all vary with changes in thp vork rate, (Silverman, et.al., 1951 .) Divers wearing lead sol2d shoes are usually unable to reach high levels of oxygen uptake except while working in deap mud, where values of approxi~ately2 liters/ninute hsve been reported, because of the r2lstively passive roi~played by his legs, (Donald Z Davidson, 1954 .) The oxygen uptake of *finnedt underwater swimmers, however, attains values of 2.5 to 3.0 liters/min., and is representative of levlfs for other athletic activities, (Donald F; Davi8son, 1954: Carroll, 1970: and Morrison, 1973,) While physical work load alone is significant in affecting diver respiration under optiaure conditions in shallow water, the additional factors discussed in the following sections are prasent in increasing 3mounts with lncrsasing depth and operating difficulty, C. GAS DENSITY Hith i~creasedbaronet ric pressure respiration at r3st becom2s slower and deeper, probably an adaptation to minimize the increasing work of bre3thiny dense gas. Decreases in both respiratory minute volume for a given ergonooletric work load and maxi~umvoluntary vantilation have been reported by severs1 investigators, (Hesser E Holregren, 1959: Hai~& Parhi, 1967: Hesser, et.al., 1968: Bradley, steal,, 1971: Rorrison & Florio, 1971: and Schaefer, et.af,, 1971 .) Decreasing respiratory rates during rest and aoderate exercisb with increasing pressure were also found, (Hesser E Holmgron, 1959: Russ~ll, 1971: and Harrison, et.al., 1376 .) Figure 1 illustra tes thci i~creasedtidal volunaa, (decreased rlspiratory rate), for a given ventilation at 4 APA compared to 1 ATA, (Morrison, 3t.ai., 1976.) In trainzd surface swimnors, however, increased rainuts volumes and oxygen uptake and decreased swimming times wer* reported with cxy-helium breathing, {decreased gas density), corapared with oxy-nitrogen or oxy-argon mixtures during maximal performance, (Keb ka lo E Ponomare v, 1971. ) For gas densities less than six, relative to air at 1 ATA, aaxiaum inspiratory and expiratory flow both vary inversely with approxinately the square ro3t of gas density, prirtlarily due to turbulent flow in the airways, [Buhlmann, 1963: and Wood G Bryan, 1971.) Increased airway resistance and reduced maximum breathing capacity are also effects of high pressurs causzd by the increaszd density of the breathing gas, (Harshall, I t.al., 1956: Daugherty 6 Schaafer, 1968: Schaefer, %t.al., 1971: and Morrison E Butt, 1972.) High molecular weight gases of equal density have been found to produce similar respiratory changes, (Lord, et.al., 1966.) Phis progressive increase in expiratory resistance and d@cr+asing maxima 1 expirstory flow with depth, rather than the increase6 oxygen cost of breathing, has been suggested as the limiting respiratory factor in diving, (Glauser, et.31., 1967: and Varene, et.sl., 1971.) Added ncn-elsstic breathing rnsistance has been foucd tc r~sultin an increas~drespiratory cycls tiat, particularly for the expiration phase, with acc~mpanyingdecreased peak expiratory flow, (Cair, & otis, 1949,) The relatively shortened inspiratory phasa with rasulting higher peak inspiratory flows, Bay thus cause inspiratory uork to be greater than expiratory work for equal resistances. This is supported by Silveraan's findings, (1951) , that exercise tolerance is less with expiratory resistance than with an equal. inspiraiory resistance. In additton, the mechanic31 efficiency of extra work is less in expiration than inspiration and the expiratory reserve volume incmases with increasing rssistanc~,favoring the? muscles of expiration, (Cain E Otis, 1949.) In a study by Campbell, (1957), unct>nscious patients made no expiratory eff~rtwith expiration resistances of 15-20 cm. H20, rather, the depth of inspiration was iccreased until the elastic recoif of the chsst and lungs cvercaae the added r2sistance. D. EXTERNAL RESISTANCE At 1 ATA reduction in work capacity, oxygsn consumption, and pulmo~aryventilation with the addition of external resistance to breathing have been reported by several invzstlgators, (Silvermar, et.al., 1951: Cooper, 1960a: Craig, et-al.) At Q ATA Plorrison, et-dl., (1976), found lover oxygen up takes for given work loads while breathing from UBA than without external breathing resistance. This is an opposite effect to that resulting fr~rnthe internally gsnerated resistance of increased gas density described aarlier, and increased oxygen rec~veryconsumption values have been recorded that Bay partially axplain this, (Thompson E Sharkcy, 1966.) Bdaptatiocs to fxtercal resistance have been noted by several authors, {Goff & Bartlett, 1957: Doughterty 5; Schaef?r, 1968: and Yatson, 1972.) Maximal tolerable inhalation resistance has been given as 75 em, H20, (Freedman E Campbzll, 1970. ) Undar prolonged conditions, Janney, (1959), reconmended exhalation arid inhalatior resistances of 5 cm. H20/(liters/sec) at 1 ATA and twicr? that at 5 ATA. E. ADDITIOWAL FACTORS **There is a tremendous difference between a diver in the (dry) chaatber and a diver in water," {Bradiey, 1971.) The caus;s for this are ccld, hydroststic pressure, vet immersion, suppcrtive difficulty in jobs rquiring force application in an ess2ntially weightless environment, and psychological factors relevant to environmental hazards. The first of these, cold, is probably the most i~portant additional factor. One of the body's respDnses to excessive heat loss is an increase in metabolic rate, Oxygen uptake increasas f run 0.5 li te rs/~in. to 1.5 liters/min. during sever? shivering at rest, and continues as lonq as skin ?nd core temperatures remain low, [A~thonisen, 1969.) On land, warming may be accomplishad through exercise, but underwater, exerciss may actually increase cooling as a result of water flushing through or past the diver's suit, [Hayward, et.al., 1975.1 This heat loss occurs because the conduction of heat through water is 20 tines greater than that of air at the surface, [Keatinge, 1969.) Respiratory heat losses, especially during Heliun/Oxygen diviny operations also play an important role which may not be adequately reflectrd in chamber tzsts when combined with immersion heat loss. Cold air inh313tion results in a significant increase in inspiratory resistant.., probably as a rasult of mild local airway obstruction, (Guleria, et .a1 ., 1969.) Ir, Arctic Helium diving, atasking of the onset of shivering was found to occur during heavy work loads. In some cases contirusd exposure resulted in inadequate ventilation due to pulaonary edema, (Nuyttan, 1973.) Although ~ininizingheat loss during iamersion has received auch a ttention, (Keatinga, 1969: @ebb, 1975: and Hayward, et.al., 1975) , it remains a problam for the working diver. Although a particular UBA may not be found to be restrictive at normal work levels during chambpr t~sts,use of such apparatus by a cold, shivering diver could result in performance impairment even at low vork loads as a result of C02 retention or dyspnea, (Arithonisen, 1969.) A second iaportant additional fact or 1s hydrostatic pressure. Oper, circuit damacd underwater ~reathingapparatus supplies breathing gas to the diver at the ambient pressur2 sensed by the diaphrag~of the regulator. Because this pressure is usually not equal to the external arnbiant pressure at the level of the lung centroid, the center of pressure of the lungs, this imposes a hydrostatic imbalance upon the diver's respiratory system in addition to the resistive loading of the bre3thing apparatus. Correction iri work of breathing calculations must bs mad* for this additional external load which varies with diver inclination frats the horizontal. This correction has an important cqnsequence. slthough the effect ~f hydr~staticpressures on infialarioa and exhalation pressur2s is equcil 2nd opposits, acd thus does not alter the total uork of breathing, it may cause a large distortior, in the balacce of inspiratory and expiratory work, and an increase in the actual uork of ths respiratory muscles. In addition, excessive levels of negative pressure breathing way result in advsrse pulmonary sffects in the form of atelectasis, apparently as the result of airway closure, (Lundgr3n, 1973. ) The effect ~f imaersion on intrapultnonary pressure was studied by Jarret t, (1965) . Subjscts Here supplied breathing gas via an oral-nasal mask. The center of pressure of the i~mersedchest, (the lung centroid), was hund to lie 19 cm. blow and 7 cm. posterior to the supra-sternal notch, A d?termlnatio~of ths most comfortable breathiny gas supply prsssure during inimersion, termrd the '~upnoeicpressure, ' was made by Paton and Sand, (1947.) subjects were supplied with breathing gas usicg mouthpiece and noseclip. The eupn~eicpressure was found to be at the lzvel of the supr3-sternal notch for prone and supine positions, In the vsrtically upright position the eupzoic pressure was above the notch at rest but increased to appr~schthe notch at hkjher ventilation rates. iJithout the supportive asslst3nce of the oral-nasal mask positive mouth prlssure with mouthpiece alone did not a1low simultansous complete chest relaxaticn and retention of the mcuthpi2ce, accounting f~r differences in test results, (Jarrett, 1965. ) Thompson and HcCally, (1967) , investigated this preference of immersed subjects to breathe at a nagative pressure relative to thz chest, rather than at a msan external thoracic prpssure and confirnied Jarrettys findings, subjects breathing through mouthpiece, facemask, and h~lwet with intrapulmona ry uressure variations found large transthoracic pressurs gr3dignts subjectively more comfortable than slight incrqases in transpharyngeal prsssurE. These differences are thus a result of the influence of pressure sensations in the upper airways on th3 subjective selection of comfortable pressure. As it is not possible to position the denand valve at the lung centroid, the ichalation and exhalation effort experienced by a diver varies as a functi3n of his orlsntatf on, OfNeill, (1 97O), calculated ths hydrostatic imbalance imposed by rebreathi~gapparatus as a functior, of diver oriertatior*. In additioc, he designed a counter-lucg breathing system with two secsitive relief valves on the chest and back at lung centroid level t3 give minimum hydrostatic imbalance at all diver orientations. There has bcen no coaparable work to quantify hydrostatic pressure effects of open circuit breathing apparatus. In testing of apparatus, only the pressure-flou characteristics have normally bsen considered uhile inspiratory and expiratory work, and hydrostatic pressure imbalance have generally been igcored. Sterk, (19731, has emphasized the need for underwater breathing apparatus t+sting in situ. The inclusion of hydrostatic pressure values in work of breathing calculations is essential in calculating the relative contribution of inspiratory and expiratory work to thl total respiratory work demanded by ths underwater breathing apparatus and in developmant of satisfactory physiological design criteria. PART 111 . EREATHING APPARATUS EVALUATION The various types of UBA all have one built-in disadvantage; resistanca to gas flow, (Sterk, 1973,) k'hile a csrtain amount of resistance can be toi2rated by the diver, the fact that it is an addition81 stress flakes its minimizatior. desirabla to snsure that respiratory flow is limited priaarily by the diver's lungs, {Bradley, 1973.) This is complicated by the fact that what saams acceptable at the surfaca may not be so at depth, and tests 3f UBA nrust be adjusted according to worst case employment, A. SOURCES OF HECHAMICAL RESISTANCE najor sources of UBA irepedence are a result of poor check valve design, inadequate ~rifice size, and radical r~directionof flow. Significant variations in the ease of breathing through units of the same model, apparently the rosult of inadequate fabrication control, have been noted, (Bradley, 1973.) If it is assumed that the gases involved in the diver's breathing supply behave as ideal gases, then; P*V=n*R*T where P = absoiute pressure of the gas V = gas volume ri = total number of mol+s ~f the gas R = universal gas constant 9 = absolutl temperature of th3 gas Ideally, for the conditions of constaiit body and environraefital temperature at depth, gas density is an approximately linear function of total pressure, P. The gas density, in turn, affects tha Reynold number which govPrns whether turbulent or laeinar flow conditions sxist for a particular situation: Nr = p * d * V/A where Nr = Reynold Number p = gas decsity v = linear tube velocity of the gas d = tube diameter A = gas viscosity The large airway cross-sectional areas ard low peak flows 3f gas &ask and filt3r type respiratory protective devices aake their resistance directly proportional to the air flow rate through the canister. Small tube diameters and hic~herpeak flow rate for scuba units, however, cause their flow charact~risticsto bs ess3ntially turbulent even during quiet respiration, The pressura caused by the elasticity of rebreathing bags found in closed and seai-closed circuit scuba further adds to respiratory resistance, (Cooptr, 19603.) Suggested methods of r4sistance reduction in the lstt2r have included the provision for a second breattic? Sag and placemsnt of the 3xhaust valve as close to the mcuthpieca as possible to reducq flow lcsses, (Riegel, 1970,) In the presence of th3 turbulent flow conditions snc3untered in UBA, respiratory work increases with minute volume and absolute pressure. Demand inhalation from orifice-type SCUBA regulators essentially delivers constant mass flow per unit time for a given valve apening. Thus voluae delivery at depth coapared to surface volume delivery will be the reciprocal of the absolute depth pressure ratio. Because Ui3A exhaust valves are not simple orifices, expiration resistance at dlpth Is more difficult to estimate from surface values. A reduction in inhalation resistance is achieved in many UBA through venturi action to increase de~andvalve pressure drop relative tc the mouth prassur?. Ths initial opening resistance, however, is not affected by tha venturi, Perhaps the most importact UBA devtlopment from studics to specifically minimizs dlmand regulator breathing resistance at depth has been the pilot valve regulatcr, uhich utiliz+s a small downstream pilot valve $3 generate air flow for air supply valve activation, (Christianson, 1975: and Scubspro, 1976.) Such optimally designed regulators have dynamic inhalation and exhalation pressures with little hystzresis, stable inhalatioc resivtanct without freeflowing, and inhalation pressure essentiaily independent of operating depth. If the work of breathing becomes li~itingto man in the sea, mechanically assisted inspiration, co~siderably di~inishingrespiratory impairment at depth by d~creasing inspiratory work, my be an even better s~lutionthan 3 simply passive UBA, (Hood E Bryan, 1971: and Uhl, et.al., 1972.) B. TESTING AND STAWDBRDS Until recently, evaluation of divsr breathing apparatus was limited to the often unreliabl* subjective responses of divers, (Bradner, H., 1953: Bradlly, 1973: and Hughes, M., 1974.) Because of adaptation by the diver to the saw variations in breathing work as th3se being investigated, this has been useful only for the rioting of gross dzficiencies in respiratory demand and not for the comparative measurement cf such resistance, (Doughterty E Schaefer, 1968: and Goff & Bartlett, 1957.) With the aia towards design inprovement, standards for allowable resistance of respiratory protzctive and life support devices were suggested in 1945, (Silverman, et.al., 1951.) In a later study, Cooper, (1960b), f~undthat human r~spiration during respiratory uork agairist an external resistance closely approximates a sine wave, and thus human sirnulatior, using a sine wave pump, instead ~f physiological ttsting, is possible. Such studies forna a useful basis for similar ccmparative evalustion of UBA. Pressure and volume measurements of breathing apparatus whzn ventilated by a sine wave pump give valid estimates of the external respiratory work otherwise performed by the diver, [Cooper, 1960a.) Most of thqse simulators have relied upon catn driven piston and cylinder arrangEments. This has the advantage of bzing able to pr3duce either uniform sine waves or allow for pauses iu the breathing cycle, (Adatas, et,ai., 19 50: Nelson, @teal., 1972: and Wilson E Harrod, 1956.) The only breathing resistance standards for URA in operation are peak inhala tion and 5 xhalation pressurz limits for open circuit SCUBA establishla in ths early 1950's by U.S. Navy BIL-R-2416911, and MIL-R-1 955A. Test protocol for these limits uses a respiratory simulator at a tidal volume of 2 liters and 20 breaths per minute under hyperbaric chamber dynamic wet conditions to measure peak inhalatioc and exhalatior, pressures. Regulators meeting 8. S. Navy specificatiocs must lie within the acceptance band of peak pressure as a function of depth to 199 feet sea water, as shown in Figure 2. A need for downward revision of the established limits and possible r2place~entwith standards of extercal work of breathing, a valu-l which has especially greater significance with the neck seal helmets currently used in ccmtaerciaf. oil fiold diving, has been noted by several authors, (Coopqr, I%M: and Reimers, 19?3.! Co~p~r'sstandards spxified that the maxiinurn work of breathing for the apparatus, (kg. a. /Bin.), should not exceed one-f3urth of the minute volumz, (liters/min.) The r~camraendedrate ci raspirstory w~rkwas one-half of this, ~xpiratorywcrk percentage of ths total work of breathing should not be more than 501 at high minute volumes. Tests uere to be performed using sinusoidaf ventilation on the apparatus with tidal volum2s of 1, 2, and 3 liters and raspiratorg. frequencies of 20, 25, and 33.3 breaths per minuto respectively. U.S. Navy WL-3-24169A (SHIPS) underwater breathing apparatus acceptacce crit~ri a, Peak inspiratory and expiratosy resistance, (mm H20), as a function of dspth, (FSW.) b PER1 EXP JRRT J ON RESJ STRNCE CI PEM JNSPJRRIJON RESISTRNCE OEPTH (FSW) D+spite tht present liatited criteria for evaluation, UBA submitted to the U.S. Navy and the comercial diving industry for wnsideration and adoption continue to be unacceptable when subjected tc dynamic wet tests at depth, (Gibson, 1975 & 1976. ) Measured vantilatory powar requirsments for a recent semi-clzsed circuit UBA have oxc eeded Cmper's standards evPn at low ventilations, (Sterk, 1973.) The pi,.ot valve ragulatcr described earlier represents an achievement in minimizing diver respiratory work requiremants. The co~binedeffects of cold, exerti3n, and carboc di~xideretention must be included in establishing exparimental limits for respiratory work, (Anthonisen, 1969: Guleria, et.al., 1969: Lindbergh, 1967: Morrison, 1973: and Nuytten, 1973,) Subjects studied in hyperbaric environm2nts without using breathing apparatus exhibited pulmonary responses suggesting that divers braathing oxy-helium gas mixture at a pressure of 2,000 FSW, (an ata~sphereabout ten times as dense as surface air), may successfully perform modarate exercise, (knthonistin, et.al., 1971 .) This is, 3f course, provided that the diver's equipment does not complicate his existing stress, performance in the field has shown that the ideal IJBA hss yet tr, be att;liced. Bithin the last few years commercial diving requirements have extended to depths greater 'ha2 1,000 FSW at offshore oil rigs, (Hughes, 1974: and iiuyue~ir:, 1973.) Eany previously acceptable UBA designs havs consequently become at best marginal due to insufficient delivery volume or unacceptable r%sistanc$, (Bradley, 1973: Lindbergh, 1967: Placlnnis, 1966: and Morrison 6 Butt, 1972.) METHODS & APPARATUS PART I: RESISTIVZ WORK/STATIC TESTS Mouthpiece pressures uere measured for steady state flow rates sf, whfr~;passibl.e, 3t lsast 325 littrs/min. for a Poseid~nsingle hose open circuit dsmand rsgulator, (Poseidon Bfg.) , and a ~rieste11 two hose open circuit demand regulator, (Yoit Mfg.) , in both dry and watsr immersion tests. using the Fortran program listed in Rppendfx A this permitted work of breathing simulations for sinusoidal flow pstterns with rninuta volumes of up to approximately 100 f iters/inin. Tho UBB was mounted either in air, for dry static tests, or in a water tank at a depth of 20-30 cm., for wet static t~sts. The deniand valve was oriented as for operation in the horizo~ta1 swimming position for both regulators, This placed the exhaust valve in the vertical position for the Poseidon single hose and in th? horizontal down position for the Trieste 11 two hose UBA. A static tube for differential pressure measurement was affix9d t3 the mouthpiece of the rsgulator, This in turn was connected to a respiration aster, (Parkinson Cowan , Eng.), via flexible tubing. A 3-way control valve joined ths flowmeter to ~ithsra low pressure air supply or to a vacumE cleansr nozzle for inhalation or exhalation measur~mentsrsspectively, Th? static h?ad tube was 5 1/2 in, in length with an internal diameter varying from 1 to 1 3/8 in. At its midl~ngththere were sight 1/8 in. diameter holes equally spaced arouna the circumference and leading into a collar of rectangular cross section 3/8 in. x 1/8 in. The collar outlet was a 1/8 in. tubing fitting which connected to the dif f erantial pressure transducer. In order to correct for ths air flow resistance of the static head tube, the pressure drop acr~ssthe tube was subtracted from the measured diff~rentialpressure values. his correction was small compared to the resistance of the prts tested, (0.5% worst case), and is in accord with values for a similar ccrrection by Cooper, (1960a.) Inspiratory and expiratory pressure-flow data for the wet and dry static tests wzre plotted for 00th UBA testsd. Air flow val.ues in liters/min. wera sel~ctedat 30 lqually spaced intervals up to maximum recorded flows. Corresponding instantaneous differential pressuras wera obtained fro@the plots. These pressure-f low paired values formed the computer program test data. Pldal volumes cf fron 7.0 to 3.0 liters werz used in simulatsd work of br~athing calcul~tions, Corresponding r3spiratory frequencies at 1 ATA wfrs detercnined froin ths formula VE = -7.2 + 21.8 * VT whers VE = Vzntilatory Flow and VT = Tidal Volume, from Horrison, (1975,) A sinusoidal flow pattern was gecfrated by the coiaputer program, (Appendix A), with maximum flow equal ton timas breathing frequency times the tidal volume, Plow values ware sampled at thirty equal titee intervals thro uqhout one generated breathing cycle and differential pressure values were obtained from interpolations of the test data. iJork of breathing was simulatsd by susmation of the increment af products of flow rate times interpolated differential pressure times the tiae intervai for one complete icspiration or expiration respectively, Total work of breathing and inspiratory and expiratory work percentages of the total work of breathicy uera also calculated. PART 11: RESISTIVE WORK/DY HAflIC TESTS Flow and pressure data was collected using a mouth held Possi3on regulator and a hack mounted Trieste I1 regulator at five different breathing ~SVE~Srepresentative of physiological reguir~rn+ntsbas+d upon studias by Morrisor, et.al,, [1976), shewn earlier ir. Figure 1. These levels were approximately 1 liter VT at 10 hraaths per ralnutz, (BPH), 2 liter VT at 15 BPM, and 3 liter VT at 20, 25, and 30 BPM, resulting in ~icutevolumas cf 10, 30, 60, 75, and 90 lit2rs/minuto respectively. Breathing frequencies were selected as b~inyphysiologically in accord with ventilatory flows as described in static tist aethods. In addition to tht UBA beifig tested, the apparatus consisted of a pfieuaatic motor, (Llar/Homec No. RD-7440-A) ; 20: 1 gear reduction unit, (Boston Gear Cst, 310-20-01) ; plexiglass piston-cylinder unit of 7.75 inch bore x 3.1 inch raaxLmum stroke with '*Off ring seal, flexible hose connsctions, watar bath for UBA immersion, an3 wood and metal support assemblies. Siae and end views of the simulator are shown in Figures 3 aad 4, Additiondl external eguipaent included one 0-1 psi differential pressure transducer, (SE Labs Eng., Ltd. Type SEllSO/O.5964.25WG) ; a ~6 inch displacement transducer, (SE Labs Type SE3 53/15OMFl) ; transducgr/c~nverter, (SE Labs Figure 3 Sid~view of respiration simulator and assccia ted apparatus. Figure 4 End view of respiration simulator showing drive train. Type SEgO5); an FM tap recorder, (HewLett Packard yodel 3960 Instrumentation Recordsr) ; low pass filter, (Hockland Systems Model 432 Dual Hi/Lo Filter); and air cylindars with control valvas and pr2ssure gauges fcr pnsumatic mator acd UBA operation. The rotary gear type pneumatic motor, rated for 1500 psi, was directly ccnnecte3 to a 7 inch diameter x 1 inch thick brass flywheel in order to minimize motor spedd fluctuations with variations in the work load and thus maintain conformity with a sinusoidal flow pattern. Reduction in the speed of rotation utilized a 20:1 worm gear reduction assembly which drove tw2 4 1/2 inch diameter spur qears through a 1 1/2 inch diameter spur gear for a further 3:1 reduction, resulting in a total 60: 1 reduction in output rpm relative to the motor. Faceplates attached to the two 4 1/2 inch spur gears had holes bored for thz placement of drivc? pins. A slotted bar attached to the drive pin on each faceplate and uas fixed to the piston connecting rod. Yith rotation of the motor at a constant speed, the two 4 1/2 inch spur gears, rotating in opposite directions, caused the slotted bar to drLve the piston in uniform sinusoidal notion without torque on the connecting rod. The centers cf the faceplate holes uere at 0.82, 1.64, 2.46, 3.29, 4.11, and 4.93 centimeters from centsrs of rotation, resulting in simulator tidal volumes of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 liters respectively from the cylinder, depznding on placemsnt of tho two drive pins. A 1 1/2 inch outside diameter plexiglass pipe connected the cylinder to the +,?st USA via flexible tubing, An air cylinder provided high prassure air to the first stage of the UBA, which was imnersed in a 2' x 2' x 2' water tank. The demand valve was oriented 3s for operation in the horizontal swimming positioc fcr both ragulators. This placed the exhaust valve in the vertical position for the Poseidon singla hose and in the horizontal down position for the ~riest*11: two hose UBA, The differential pressure transducer measured the pr3 SSU~;;? at the mouthpiece relative to a'tmospher ic pressure. Changes in diver position which result in variations in hydrosts tic pressure imbalance at the lung cantroid with respect to the demand valve were raflected by chacging the valu~of the hydrostatic pressure imbalance in the computer calculation of the work of breathing. The displacament transducer, aounted on the connecting rod end of the piston-cylinder assembly, provided inforaation oc piston vefocity and thus on inhalation and exhalazion air flow. A separate air cylinder with low pressure regulator and control valves regulated the speed of the pnsuniatic motor for siaulation output of respiratory frequericies in the range of 10-30 broaths per minuts. The low pressure supply was also cocnccted to tke respiratory pump in back of tne piston. A 1, x 1' x 6" open bottom box was immersed In tho tank to a depth approximately equal to that a•’ the drmdnd valve acd wss zisc cocriected tc the cyiicd=r in hack of th~pistoc. This provided backpressurs to offset th~hydrostatic load or the simulator during oxhala tion, thus minimi zing appar3tus speed variations. Fire hazard in a comprsssed air txvirocinsnt auring proposed futurs hyperbaric testing of the apparatus decided the use of a pneumatic rather than al+ctric motor. Th? choice of this psrticulsr mode of sin@ uav- gt.neratior!, rather than through the use of cams, was made due to the difficulty and expdnse in 0btainir.g accurately milled cams, 3lthough these could be substitued at a later date, as in a simulator by Nelson, (1972.) Soma points of consi32ration with both this device and those in previous works wore backlash in tht mechanism of th>2 pump, fluctuations in motcr rotation with load vsriation, and distortion resulting fro& binding forces, Thsse sources of srror were compensated for by the dispi3csmsnt transducer ia calculating gas flow rates, A cornparisor betw~snactual arii predictsd av2raqe flow rdtas was made tc check for leaks around tne piston O-ring seal. Actual average flou rates were obtained from flow m2tar volume and time measurem*nts, Predicted flow rates nsre cillcufated from piston stroke, cylinder Dore, afid rpm. Discr?pzncies of l+ss fransduczr outputs for piston dispiaczment and diff zrerltial pressure werz collected on an FH tape recorder. Signal to noise ratios were improved by sdjusting the displscsmzct transducer p~sition to jive small positivs signals in the minimum position and zaro offsetting the dif f areritial pressure siunal using a proamplifisr. Tha pressure signal was filterad using a 10 fiz. cutoff low-pass filter. The two channels of izformation werE then sample3 at 60 times per second and 33 s2conds of 2ach tdst, {the maximum coaputer storage capacity), were digitized OL a PDP 11 computer, (Digital Equip, Corp.) This permitted analysis of at least four ccmplete breathing cycles at 1 liter tidal volume aca approximately 10 brea ths/nin, frequency, the slow3st dynamic setting, Digitizzd Jkplacemznt and prassure iriforrnation was then transmitted to an IBH 370 computer far dat3 storage and processing. Sampling rate was selscted to exceed twice t Le frequency of any desired ;nformation. The computer program, (~ppenllixB), first set up data arrays, initialized intern31 variablts, and established a time increment equal to 1/60 second, (the reciprocal of the sanapling rats.) A five point smoothing fofaula dzscribed by Lanczos, {1967), was used to calculate velocity from dispiacement data. Iritia: inspiratory or expiratory incoiaplste half cycles were rejected by testing for change in direction of vslocity, Compltto respiratory half cyclos were identified in the sane manner. Correcti~nsfor the immersed depth 3f the demand valve regulator diaphraqm and offsetting of the differential pressure values were also included. swiisiulng position hydrostatic pressure iatbalance data froln the results of Part 111 permitted calculation of variations in inspiratory and expiratory work percentages of the total work of breathing. Dsad space in ths respiration simulator cylinder and connective tubing to the UBA necsssitated an additional corrsction factor for the piston displacement values in the computer program, Compressicn of the air in the dead space with each pump exhaust, (UBA inhalation), caused a decrease ir, the ~f fective initial piston displacemsnt and thus a skewing of the sinusoidal flow. Pump intake, {UBA exhalation), resulted in a similar but slightly smaller effect in the opposite direction. zork of breathi~gwas calculate4 using the pressure-flow data by summation of the incremental products of flow rate tim+s difterantial pressure times the time interval. Tidal voluae, respiratory f rsquency, minute voluiae, resistive 3nd hydrostatic work components, and total work of breathing were also calculated for each simufdtor run. PART 111: HYDROSTATIC PRESSURE IBBALAWCE The inclusion of representative hydr~staticpressur* values in work cf breathing calculations is essential in determining of the relativa contribution of inspiratory and 2xpiratory wcrk tc the tot31 rzs~irator y uzrk. Aft hough studies were made by Patton and Sand, (l947), and Jarrett, (1965), on the position of the lung centroid, no previous investigation could be found for measurement of hydrostatic pressure values normally encountered by divers using open circuit demand UBA. Ten SCUBA divers wers photographed while swimming underwater in five approximate orientations, (horizontal, 45 degrees up a~ddown, and 90 dejrets up and down), and in an upright work position with head erect, Divers were photographed breathing frog both mouth held single hose and back mounted two hose demand regulators, The heights and weights of the tec subjects including one female, (LW) , are shown in appendix C, A marker was tapsd to the sternum of each subject immadiatoly beneath the supra-sternal n~tchas a point of refsrence. The SCUBA equipment was adjusted comfortably by ths diver. Harki~gson ths SCUBA cylinders provided a r3f~ri.rcescale for subs~quefitlrteasurrmlnt 3f enlargeaents of the photographic slides, (Pigures 5 and 6.) Lung centroid location, LC, as defined by Jarrett was determined froni body markings on the sternum, shoulder, and hip, and the distacce, 8, between lung centroid and the canter of the demand r~gulatordiaphragm, Hc, w3s msasureri for 2ach position. A bar placed horizontally in the background astablished th? diver orientation. Body angle, a, was defined as the angle between th2 horizontal referents bar and the hip-shoulder line. Angle h between the hip-shouldsr fibe and the lung centr~id-demand regulator lin2 was also measured. Values of the hydrcstatic pressure, Hd, coull thus b2 expressed as Hd = Rsin (a++) . Figure 5 Subject DH in a swimming orientation for hydrostatic pressure imbalance test usiag mouth-hsld regulator. Chest, tank, and horizontal reference markers are visible. Subject DM in a vertical working position for hydrostatic pressure imbalance test usiag back-mounted regulator. Chest, tank, and horizontal reference markers are visible. RESULTS PART 1: RESISTIVE gORK/STATIC TESTS Static pr~ssure-flow data uere obtained for ~othdry and w2t test conditions fcr Pos2idon singi? hose and Priests 11 two hose 3pen circuit deaand r-i?gulators. At 1 ATA plots of pressure, (am H20), as a functi~nof of flaw, (liters/rair:.), are shown in Figures 7 through 14. Prf ssure aeasurements were ~adefor both increasing and dmzreasing steady-sta te flows in order to record possible hysteresis in the UBB under test. The greatest variation b3tween incre3sing and decreasing ventilation for all tests up to 325 litersfmin. wds approxiiiistily 10 RE. ii2G. Tbz ayerags sf the Fncroaslng and decreasing pressure-flow values uas used in subsequlct computer simulations. LPesistai~cesincreased with vsn tilation for both regulators during expiration and for the Poseidon regulator during inhalation. The Trieste 11: two hose regulator, however, exhibited a nearly constant inspiratory resistance up to approximately 375 liters/min. in the dry test and 300 lit?rs/min. in the wet test. The highest recorded expiratory flow for the Trieste I1 in tho dry t?st was 151.5 liters/min. Greater exhaust flows in the dry condition caused exhaust Figure 7 Poseidon dry static inspiratory resistance, (am H20), as a function of ventilation, (liters/aia .) Figure 8 Poseidon dry static expirat~ry resistance, (ram H20), as a function of vectilation, (liters/min .) 1 1 I I 10 10.00 20.00 3b.00 ~0.00 SO. 00 LlTERS/HlN. ~10' Figure 9 Poseidon wet static inspiratory resistance, (!nn H20) , as a fu~ct10~of ventilation, {liters/min. ) Figura 10 Poseidon wet static expiratory resistance, (am H20), as a function of ventilation, (liters/min. ) Figure 11 Trieste I1 dry static inspiratory resistaace, (mm H20), as a function of ver.tilation, (liters/ni~.) Figure 12 Tfieste 11 dry static expiratory resistance, (am H20), as a function of vectilation, (lFters/min.) TRIESTE ORY STATIC INSPIRRTlON O INCRERSINC TRIESTE ORY STRTlC CXPIRFITIOW O INCRERSING B OECREISIWG Figurs 13 Trieste I1 wet static inspiratory resistance, (cnm H20), as a function of ventilation, (liters/min. ) Figure 14 Trieste 11 wet static expiratory resistance, (am 820) , as a function of ventilation, (litsrs/min. ) V~~VIflutter with resultant cocsiderable pressure fluctuations. Expiratory pr2ssure increases of approximately 30 mm H23 were noted with alterati~nin the orisntation of the poseidon regulator fran thz sxhauat valv? upwards to eithsr exhaust valve vertlcsl or exhaust valve d~wnvards, {Figure 10.) The mouthpiece of ths Poseid~nis perpendicular to the exhaust valve which the rvf ore remains vertical independent of th3 inclination of the div2r to th2 horizontal, Expiratory resistance is thus independent of swimming angle, If the diver were to roll to one side, ho~ever,expiratory resistance, and consequently expir3tory work of breathing woulE be affected accordingly, Complete results of the work ~f breathing as estimated from the computer analysis of the steady state pressure flow data, together uith inspiratcry and expirat~rywork values and percentages of total work, are contained in Appendix D, simulated work of breathing, (kg.m./~in,), as a function of sinus~idalventilation, (li ters/min. ) , are shown in comparison to dynamic test results for th~Poseidon in Figure 21 and for the Triestn I1 in Figure 22. Also shoun are Cooper's, (1960a), maximum and recoaamended standards for respiratory protective aevices. PART 11: RESISTIVE UORP/DYNAPlIC TESTS One ATA pressure charlcteristics of a Posdidon mouth held and a TrifSt~11 back mounted regufat~rwere measured during sinusoidal vectilations usinq a respFration simulator connected to the immersed UBA. Test canditions had tidal volumes of 1, 2, and 3 liters and ventilatory rates of up to 95.9 liters/min, for ths Poseidon and 80.1 liters/iliin. f~r the Trieste 11. Pressure acd flow data obtained fron the dynamic tests at a tidal volume of 2 liters are piotte3 in Figures 16 and 17 for the Poseidon rzgulator, and in Figures 19 and 20 for th& Yrieste I1 ragi;:atcr 3s a fu~ctloncf sample number, (6O/sec. ) Piston displacements from which these pressure and flow curves are generated are dapicted in Figures 15 and 18 for Poseidon and Trieste XI rsgulators resptctively. Data is shown in ca. as a function of sample number for both uncorrected and compression corrected displacements. Completo results of the dynamic work of breathing conputfr calculations are cor~tainedin Appendix E f~rtbe Poseidon ragulator and in Appendix F for tne Triesto 11 Figure 15 Uccorrectsd and cornprassion correc tea piston displacement, (cm.) , for Poseidon regulator, 1 ATA wet dynanric test at 2.0 iitors tidal volume and 17.7 breaths/min. respiratory frequency, Figure 16 Flow, (liters), as a function of time, (seco~cls), for Pos~idonregulator. 1 ATA wet dynamic tsst at 2.0 liters tidal volume and 17.7 breaths/min. Figure 17 Pressure, (ma H20), ds a function of time, (seconds) , for Poseidon single hose regulator. 1 ATA wet dynamic test at 2.0 liters tidal volume and 17.7 brea ths/iain. Piqurz 18 rrj,,corractad and conprtssion corrected pistcn displaceiesnt, fcm.) , f 3r Trieste I1 regulator 1 ATA we+ dy~amictest at 2.0 liters tidal voluiae and 20.8 breaths/min. respiratory frequency. Figurs 19 Flcw, (liters), hs d function of time, (seconds), for Tri2sta If regulator 1 ATA wet dynamic t,.rst at 2.0 llters tidal volume and 20.8 breaths/min. rtspiratory frequmcy. Figure 20 Pr+ssure, (~iuH2C), as a fucction of time, (seconds), for Trieste I1 two hose regulator 1 ATA vet dynamic test at 2.0 liters tidal volume and 20.8 breaths/lain. respiratory f reyueocy. tagulator. Total wcrk of br~sthi~g,(kg.m./min.), , as a fucctios of sinusoidal flax, [fitsrs/iuin.f, 2s plott-.d in Figures 21 and 22 respectively. fcspiratory and expiratory work ccmponrnts of the total wor~of br3atriicg for the two rsyulators are siailarly shown as a function of ventilation ic Fiqurss 23 and 24. The work of breathing was calcu~at~amanually for ore test run from th~pr2ssure-tim? and flow-tlme plots, (Figures 16 and 17, ar.d 19 ana 20), as a check on tn? rssuits of the comput2r calcuiations. Ths ccmputer program based calculations used an equai time interval for work of breathing apprcximaticns according to the =xpression: P = Pressure V = Volume t = Time Banual calculations for tr,2 work of hreathsnj, however, w+rs dsrived from thr summaticn of ar. nyuai vcluin? increm2nt times the dLfferential pmssure at each incrtmsnt interval throughout the braathing ha lf-cycles according to ths expression: The diffarence between tha two methods was 4.52 and was within the ~stiraatedaccuracy of the mariuai caicuiatior.. Figure 21 Htsistive wor~cf oreathing, (kg.m./mic.), as a function of vc:r.tilatio~!,(liters/ain .) , far Poseidon mouth-held open circuit underwater br~athingapparatus. Dynamic testing of apparatus immersed in water. Haximum and recommendad standards by Cocper, (1960s), are als~ shok-n. 1 fl7R U,B.R. PERFORllRNCE O CUUPER HQX. SIRNOQRO 8 COOPER RECOHHENOEO A PbSEJObN ORY SlCIlJC 6 PUSEJOON NET S'IR7JC 8 POSEJObN NE? OYNRHJC Figure 22 Resistive work of breathing, (kg. mi,as a function of v~ntilation, (lit~rs/min.], for Trieste 11 back-mountsd open circuit underwater breathing apparatus. Dynamic testing of apparatus immersed in water. Haximum and recoamended standards by Cocpor, (1960a), are also shcur,. COOPER HRX SlRf4ORRO COOPER RECbHHEtiDEO IRIESTE 11 URY STRTJC IRJESIE JJ UE7 STRTJC 1RIESTE 11 NET DINRHJC Figur2 23 Poseicion inspi ratory an3 6xniratory resistive work of breathing, (kg. m./min.) , as 3 function ~f vertilation, (liters/min. ) Dyrlamic testing of apparatus immsrsed in water, figur? 24 Trieste I1 inspiratory and expiratory resistive work cf breathing, (kg. m./min.), as a function of vectilation, (liters/min.) Dytareic testing of apparatus immersed in va ter. PlSE l DON O INSPJRRTION C1 EXP IRRT I ON IRIESTE I1 13 INSPIRRTIUN D EXPIRRTION 1-- 7 DO 20-00 YO. 00 6b.00 eb-oo ~bo.oo VENT I LRT I ON [L I TERS/W I N. I PART 111: HYDROSTATIC PRESSURE IHBALANCE Tho hydrosta tic pressure dif f srenco between the div=lr s lung caitroid acd the demacd r9gulator diaphragm ~f his open circuit UBA was measured directly from the slides for ten divers a~dare shown plottsd rtlatlv-2 t3 swiniming angle in degrees for mouth h?ld, (Figure 25), and back mounted, (Figure 26), regulators respectiveiy. The mean values of R an d were first determined for 2ach subject in the swimming position in order to obtain a mtan curve, Hd = Rsin(a+ ), representative of the group. R and valu~smeasured in 2ach positior! were slightly differnnt. With the two hose regulator this uas du? to small novements of the equipment relative to the diver, but with the single hose regulator variations resulted from movements of the a3uth and head. The Inaan R and for all ten subjects were then determined from individua 1 mean values. Standard deviations were calculated using the differences, (Hd - Hd ), between the teean curve and the individual data points m2asured from the siidzs. The mzan value of Hd when swimming was defined by the equation: Hd = 40.0 sin(a-14.5 ) + 4.3 cm. H20 for aouth held regulators, and Bd = 27.9 sin(a+33.8 ) + 2.9 cm. H20 for back mounted regulators. Those ?quations apply over the range of diver orien+ations -90. horizontal. Figure 25 variation in vertical distance betweer. lung cectroid acd demand vafv*, (cm.), as 3 function ci diver orientation with r2spect to ths horizontal for mouth-held dzmand regulator. ANGLE (DEGREES) SINGLE HOSE REG. HYDROSTRTIC HERD 0 SUBJECT TB + SUBJECT JM 13 SUBJECT HC X SUBJECT NS A SUBJECT PH X SUBJECT LT O SUBJECT OH 9 SUBJECT HW X SUBJECT OM X SUBJECT LW - HERN Figure 25 Variatic~13 vertical distacce b2tweec lucg centroid arid demand valve, (cm.), as a fuccticr, cf diver =rientation with respect to the h~rizontalf3r back-mountea demand ragulator. FINGLE (DEGREES) TWO HOSE REG. HYDROSTRTIC HERO 0 SUBJECT TB + SUBJECT JM I3 SUBJECT MC X SUBJEC7 NS A SUBJECT PH X SUBJECT LT 0 SUBJECT DH 9 SUBJECT HW X SUBJECT DM X SUBJECT LW - MERN nean hydrostatic pressure was calculatsd f rcm the data for each subject in an upright working position with head erect. A working position mean valu~of: Hd = 24.1 2 3.7 cm, HZ0 was calcuiated for a mouth held rzgulator, and Hd = 24.7 2 2.6 cm. A20 with a back mounted ragulator. ltlarly all open circuit UBA presently available are similar in the placemlnt of the demand diaphragm relativs to either rtlouthpiece for mouth held or cylinder mounting for back mounted. These results are therefore considered to be reprasentativlt of open circ ui t scuba irresp~ctiveof apparatus manufacturer or model, Static test calculations of the work of brzathinq were greater for the Poseidon rtgulator during immersion than during dry testing. Steady state pressure-flow data, (Piqurss 7 through lo), showed this tc be the result of an increase in exhalation rssistance at all ventilations. Large changes in poseidon exhalation rasistmcs were noted with variation in exhaust valve orientation, (Figure 10.) It is suggested that during immersion, the formation of bubbles and their subsequent release from the area of the exhaust ports caused increased expiratory pressure f~ra given flow rate compared to the non-immersed condition. Cooper recom~tlended that the work of breathing for r~spiratorydevices, (kg. rn. /min.) , cot exceed one-eiqhth of the ventilation, flit~rs/min,), (196Oa.) staady state irtlraersed work of breathing at 1 ATA exceeded this at approximately 81 liters/min. for the ~oseidon, (Figure 21,) Trieste XI regulator static tssts found inspiratory acd expiratory resistances, (Figures 11 through 141, and work of breathing, (Figure 22), to be greater in the dry condition than when immersed, Differecces in expiratory resistance way have been largely a result of the same exhaust valve difficulty which abbreviated the dry steady state testing. Ste3dy state wcrk of breathing undzr w2t conditions at 1 ATA for the ~riaste11 r~qulat~rexceeded Cooper Is recommended standards at approximately 92 litirs/min., (Figure 22.) ~ynauicwork of breathing at 1 ATA for the poseidon UBA exceeded Cooper's r~coetmeadationsnt approximately 51 litars/min. ventilation, plotted in Figure 21. The Trieste I1 UBA under the sans conditions exceedzd these values at all vmtilations. Purthar, at the highest flow rate tested, (3 litzrs tidal volume and 26.7 broaths/min.), the Trieste If reachsd CooperSs maxiinurn limit of the uork of breathing aqua1 to ~ne-fourthof the ventilation, as shown in ~igure22. The steady state testing of both regulators was carried out in conjunction uith the dynamic testing in order to investigate the validity of static determioations of UBA work of breathing. The obtainmsnt of similar results would indicate that UBA psrformance measurements could be made without the need for a respiration simulator. However, static work of breathing values w2re 3s much as 23.2% less than dynamic at 95.9 lit2rs/min. f~rtne P~seidonand 58.22 12ss at 80,l lit~rs/inin. for the ~rieste11. Of this diffzrencz, poseidon static inspiratory work was 42.2% lass than dynamic inspiratory work, while st3tic expiratory work was only 9.1% less than dynamic expiratory work, For th? Trieste I1 values were 75.9% lsss and 29,4% lsss re?spoctiveiy. The dynamic testing, simulating typical diver employment of the UBA, cycled the regulators through inspiratory and sxpiratory brzathing ~haseswith sinusoidal variation ic flow rate, Hysteresis losses due to damping during opening and and closing cf the tilt valv~inspiratory mechanism and water flow resistance with movement of the demand diaphragm probably caused increases in work of breathing compared with static testing estimations. Exhausting of water influx into the exhaust ports during ths first stages of exhalatior,, and non-steady state exhaust bubble formation may also have affect3d the work of breathing, Because the differences betwean static and dynamic tzst results are both large and difficult to correct, it is concluded that steady state testing is not a valid method for work of breathing evaluation of UBA. Hydrostatic pressure imbalance, as shown in Figures 23 and 24, varied with swimming orisntation by approximately -+ 40 c~.H20 when using mouth held regulators and 2 28 cm. 820 with back mounted r~gulators. In addition, hydrostatic pressure imbalance with mouth held ragulators is also afE..sctsd by head position, tfze amaunt of passible variati~r, i~crzasingas the swimming angle deviates from the horizo~tal. This is rzflected in the difference between hydrostatic pressure imbalance measured when the diver w3s swimming upward, (+40 em. R20), and the upright working position where the divclr was looking horizontally, (424 cra. H20,) Hydrostatic pressure imbalancs has a significant effect upon icspiratory and ~xpiratorywork. Figures 29 and 30 illustrate inspiratory and expiratory work as percentages of the total respiratory work for a mouth held and a back mounted regulator at 1 ATA at high ventilations plotted with respect tc swimwi~gangle. The percentages shown without hydr~statximbalance indicate the external respiratory load that would result if the dsmand valve were placed in the idsal position at the lung centroid. Percentages of total work were determined frcm the pressure-flow measurements made during the vet dynamic tests. Negative external expiratory work may rasult in a reduction in the total expLratory work and h~ncea lesser inv~lvementof the respiratory muscles, N agativz hydrostatic work exceeding the combiced internal and external resistive work, will result in braked expiration, and thus cause a Figure 27 The inspiratory work percentaqe of the total wcrk of breathinq as a function of divrr orientation with respect to the horizontal. Based on 1 ATA dynamic testing of a mouth-held open circuit regulator immersed in water, Biguro 28 Th9 inspiratory uork percentage of the total ncrk of breathing as a f unctioc of diver orie~tation with respect tc ths horizontal. Bassd on 1 ATA dynamic testinq of a back-mounted open circuit regulator imm?rsed in water. a'- POSE 1 DON TRIESTE I1 1 I I 1 1 1 30.00 -60.00 -30.00 0.00 30.00 60.00 90.00 FlNGLE (DEGREES) Figur3 29 Inspiratory and axpiratory work expressed as a perczntaqe of tbe total work of breathing. The figure shows work both with and without hydrostatic imbalance. Bassd on 1 ATA dynamic testing of a mouth-held open circuit regulator at 75.6 liters/min. ventilation imm~rsedin water. 1 R7B SINGLE HOSE: 75,6 L./Mlfl, Figure 30 Icspiratory and expiratory work expressed as a percontayz of the total ~orkof breathfng. The figure shows work both with and without hydrostatic imbalance, Based on 1 ATA dyna~ic testing of a back-mourtad open circuit regulator at 80.1 liters/min. ventilation immersed in water, EXPIRRTORY WORK IHHERSEO IflSPIRfiTORY WORK N/b IHBfiLfiNCE - \ EXPIRR1ORT WORN N/O IHBRLRNCE r 1 60.00 90.00 1 RTR TWO HOSE: 80.1 L./HIN. greater involvemect of the inspiratory muscles. This lattzr condltioc imposes an unnecessary r2spiratory load upon the diver. Zooper's suggested standards for respiratory protective devices, (1960a), included the racommcndation that at high ventilation rates the fraction of work dons in expiration should not be Bore than 50A, The effect of hydrostatic imbalance or inspiratory and sxpiratory work decreases with the Increase in UBA resistive work with *ither increasing ventilatlcn and cr increasing depth, (Figures 27 and 28.) ComparFsons of Figures 29 and 30 show that at 1 ATA the back nountsd two hose regulator provides a greater range of diver orientaticns havirg expiratcry work less thar SOX of total work of breathing. In terms of balariclng thz work of breathing between inspiration and sxpirati.311 the back mounted regulator may thus be preferable aspecially if the divar's body iriclinaticn is predominately in other than a horizontal swimming position during the dive. Whether tho divar should breaths sgaiast a positive or n2yative pressure depends to as 2xtent upon zhe ~agnitudeof thl inspiratory and expiratory resistive work of the particular deaacd regulator in use, Thus if expiratory resistive work is larger it is best to breathe against negative pressure in order tc shift part of the lold to inspiratioc, thereby making use of hydr~staticpressure imbalance to obtain the best ratio of insp~ratoryand expiratory uork. Considering Coops rvsrecommendations f ~r limiting expiratory work, and the comfort indicated pressures found hy Patcn ar,d Sand, (1947) , 3nd Thompson and IvlcCaily, (1967). it is probably best to incorporate negative pressure br3athing provided leve 1s a re not sxcessive, CONCLUSIONS The respiration simuf ator uLth sFnuso;dal vantilation used ic this investigation enables tha detarmination of the work of breathing for open circuit demand underwater breathing apparatus undsr immerse.i dynamic conditions. Test rasults thus give estimations of apparatus performance in torms of physiologically acceptable respiratory work loads and permit direct comparison bstwezn different underwater breathing apparatus. Steady state bench testing %as found to be not a valid m2thod for underwater breathing apparatus *valuation as 3 result of nor- replication of dynamic inspiratory and sxpiratory r~sistancss. Hydrostatic pressure imbalance as determined for various diver orientations using both mouth held and back aounted demand regulators was a significant factor in inspiratory and expiratory work parce3tages of tho total work of breathing. Respiration simulator measurements of the work of breathing for the underwater breathing apparatus tested 2xcaeded earii~rrecommend2d stacdards even at 1 ATA at ventilations within the physiological range of working divers. Adarns, H., B. IV. ElI G. KC, 1350, A Mew iiespiralory Pump. Australian J. Exp, Biof. Med. Sci., La: 657-006. Agostoni, E., and W. 0. 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Christie, 1954, Thz Vork of Urza thing iu Normal Stlbj4~t~.~linicdi Science, 13: 127-136. M?cld, J., 1963, The Control cz Hzsplratozy Praquzccy. Ar.nals N;w Ycrk Academy of Scienczs, 103; 724-728, Mead, J, 1955, iiesistance to Brzathing at Increased ~mbitnt Pressures. Proc. Symp. U. d, Physiol., Goff, L., ed., 112-12.3. aiudl2ton, J. ii., 1977, Evaiuation of Sherwood Solpac SRB-4100J aild Sii3-3000 Op2n Circuit Scuud iltguidtors. Mavy Experimental Diving Uait Hsport 5-77. Yiias, s., 1957, Ths Effect of Changes in daroiaetric Pressurz on Maxiuium ~reathingCapacity. J. Pnysiology, 137: 85P-86P. fiilier, J. N., O, D. danysnsteen, and E. H. Lanphier, 1971, Ventild tory Limitations on Exzrtlon at D5ptfi. Proc, 4th Symp. U. W. Physiol., Lambartsen, C., ei., 317-323, Morrison, J. fl., Y. S. Butt, J. T. Florio, and I, C. ?layo, 1976, Etfects of Increased 02-N2 3ressure and Braatninj Apparatus on Respiratory function. Undtrsea Biomed. Hes., 3: 217-234, ilorrlson, J. B., 1973, Oxygen Uptake Studies of ~iverswhen Pin svimmirig with Plaxiatun Effort at Deptns of 6-176 Fast. AE~OS~~CEMedicinz, 44: 1120-1 l2!L flozrison, J. B., and U. S. Butt, 1972, Effect of Undtrwatar Brz3thiLg Apparatus and Absolute Air 2ressura on Divers1 Ventilatory Capacity, Aerospacs H~dizine,43: 881-d86, Morrison, J. B., and J. T. Florio, 1971, Rzspiratory Punctioi: duririg a Sirnulatad Saturation 2ive to I, 500 Pzet. J. ~pplituPhysiolo3y, 30: 724-732. Nelso3, ;;. O., Ii. E. Johnsan, C. L. Lindekzn, and R, D. Taylor, 1372, Hespirator cartridge Efficiency Studies 111. A flechanical Breathing aachina to Slmuiat+ Human dzsi,irati.on. Am. Ind. Hyj. Assoc. J,, 33: 745-750. Nuytten, P., 1973, Deep Helium Diving in the iiign Arctic. Offshore Tech. Couf. Paper No. OTC 1779. 08Neil, Y. J., 1970, A Study of tnr Bredthing dydrostatics of Various Bag-Type Oiving Apparatuses and Description of the Two-Vaivt Toroidal &a Abalone Back-Houn t?d Design. E4uipmki:t for thz Worklny Divar, Marlne Tech. Soc. Symp., 183-211. Otis, A. , 1954, The Wcrk cL Brdthi~lg. Physiological Revi; us, 34: 449-453. Paton, W. D., and A. Sand, 1947, The Optimum Intrapulmonary Pr+ssures in Underwater Fes2iratioil. J. Physiclogy, 106: 119-138. Bzirnsrs, S. D., 1973, Simulation Tzsti~gof Divers ijreatnir!~ Apparatus. L', X. lied. Soc. Syiap. Hieg+l, P. S., 1970, Llter Plow and Hix SelectLon in 3emicioseu- Lircuit 5cutl3. Maririt Tech. Soc. J., I): 17-26. ai+g+l, P. S., and J. V. Harter, 1953, Deslyn of Breathing Apparatus for Diving to Grzat Depths. ASPiE Pub. 69-DL-22. Radriguez-Xarticez, P., A. V. Plascia, arad a. B. aeliins, 1973, The Effect of Environmental Temperature on Airway iiasistdrics iri tbt Asthmatic Child, P~dicitr. ads., 7: 6L7-031. 2.usss11, C. J., 1971, Some Respiratory, fletaboiiz and Caraiovascuiar R+sponses of Scuba Divzrs LO Increaszd Pressure and Cold, Ph.D, Thesis, Univ. cf Orsgon. Salzsno, J., E. il. Overfield, D. C. Hausch, H. A. Saltzman, J. A. Kylstra, J. S. Kelley, and J, K. Summitt, 1971, Arterial blood Gases, Hadrt tiat*, arid Gas Exchange durizg Best and Exercise in Hen Saturated at a Simulated Seawater D~pthaf 10d0 Feet. Proc, 4th Syap, U. d. Physiol., Lambertsen, C., ed., 34'7-35b. Schaefsr, K. E., C. R. Carzy, and J. H, Dough-lrty, Pulmonary Functior, arid Respiratory Gas Exchange during saturation-Excursioc ~iving to Pressures Equivalent to 1000 Feet of Seawater, Proc. 4th Symp. U, Y. Physiol., Lambertsen, C, , ed., 357-370. Scub3prc Bfg. Co,, 1976, Pilot Regulator Szcond Stage. Addenduu to Technical Manual for Scuba pro Rejulators, Cat, 101-d7, Ccmpton, Cal. Shiphard, h. J., 1967, Th3 Maximum Sustained Voluntary V2ntilaticn ic Exercise, Clinicai Scleccz, 32: 167-176. Sidor*r,k~, L., 1972, Hixicj of Gases iri thi Dzad Space of the Respiratory Tract. Byull, Eksp. Biol. %3., 73: 10-13. Siivtrmdn, L., G, toe, 2, ~ict~in,L. A. Saw,?rs, and A. H. Yanc?y, 1951, Alr Flow Measurements oa Humac Subjects nlth and without Hespiratory Mesistance it Sev3ral #=rk Rates. Aici,, I;d, Myj. Occ. Wed., 3: 461-4723. Sterk, Y., 1973, ~espiratoryMechanics of Avzr and Diving Bpparat us. Drukkeri j Elinkwi j~-Utraciit, Nethi rlands, Thorapscn, L, J,, and &. acChlly, 1967, 20;a 21 Transpharyngeal Pressure Gradients in Dzt2rmlug IritrclpuLmona ry Pressure during Immersion. Aerospace. a*d, 36: 931-935. Thompscn, S, H., and B. J. Sharxay, 1966, Physiological Cost and Air Flow Resistance of Respiratory Protective Devices. Lrgonomics, 9: 495-499. uhl, a. a,, C. V. Dyke, 3. 3. Cook, R, A, liorst, acd J. Fl. r,1972, Effects of Externally Imposea H~chacicai dzsistacce Oi, Breathing Dzns~Gas at bxercisa: iinechanics ~f B~aathii~g.A-.rospace iladicin.s, 43: 83b-84 1. U. S, Navy D~viriyManudi, 1973, lVavships 0994-1)01-9010, Navy Dept., kashington, D. C, Varene, P., H. Vieillefond, C. Lamaire, anu G, Saumon, 1974, Expirat cry Flow Volume Carves axid Venrila tory Limi tatior, of Husculdr Exercis~at Dzpth. Aerospace Medicin?, 45: 161-lbb. V~rosmarti, J., kl. E. Uraaley, sad N, R, Antnonisen, 1975, The Zffects of Increased Gas Dsnsity on Pulmoiiary Miichanics. Undersea Blomzd, Res., L: 1-10. datson, A. #,, 1972, Some Obsavations on the Respiratory Effort cf Baypipa Pldyiny. Proc, Pnysiol, Soc., 3P-4P. W3u5, P., 1'375, Cold Exposure. Ti12 Physioro~yof Diving and Compressed Air Work, 2nd ed,, Bennett, P. arid D. Elliott, sds., Wiilian~s, S, , 1975, Underwater Breathing Apparatus. The Physioicgy of Diving and Coiapr~,ssedAir Work, 2nd sd,, Bennett, P, and D. Elliott, tds., 34-46. Hiison, M. E., ar,d D, C. Harrod, 1956, Dev*lcpinint of Mechar?lcai Breather for Evaluatior? of R2spir-atory Equipmzn.t. A. M. A, Arch. Ind, Healtn, 13: 561-566. dood, L. u., and A. C. Bryan, 1971, :qechanlccl Lim~tatiorisot Ex.?rcise ~entilaticnat Iiicr~asidAmblerit Prassura. Pros. 4 th Symp. 3. k. Physiol., Lamt;drtser,, C., ;ti., 307-316. Wood, L. . and A. C. i3ryan, 1909, Effsct of Increased Ambient Pressure on Flow-Volumz Curva of thz Lung, J. Appliea physiology, 27: 4- 8. Laluel, tr., J. G. Jones, S. 8. Bdch, Jr., and L. Newberg, 1974, Arialog Computatior of Aivzolar Pressure and Airway i3tsi~tar.c~during Maximum Expirdtory ?log. J. Appii5a Physlolcgy, 36: 240-245. ~pp9ndi.xA Computer Progran for aesistive Uork/Static Tests // EXEC WATPIV S JOB 0.447/BEICB,KP=29, TIlE=2,RUE=PREE c. b Set up data arrays for flow rate and diff. press. DIREWSIOU A (30). B (30). C (3O), D (30), E (9). P (9) First 3 lines: Dry inspiration flaw rate Second 3 lines: Dry inspiration presstar3 Third 3 lines: Dry expiration flow rate Fourth 3 lines: Dry expiration pressure Last 2 lines: Tidal volume and Respiratory frequency OREhD(5,12) (A(3) .J=1,30). (B(K) .K=1,30), (C(L) ,L=1.30), 1 (~(8),R=1,30). (E (I).I=I,~), (P(N) ,N=I,9) FORMAT (10F7.0) f-t Set flow surface area in sq. cm. (0 SA = 3,14 * (2.54/2.00) ** 2 Y Set acamulator equal to zero w = 0, Sat work of inspiration squal t3 zero UI = 0, Set work of expiration equal to zero Pt = 0. WRIT1 (6,22) OIORIYaT ('O'.BX,'VT'.4X,'BESPAZ',3X, 'VENTM',4X,'HI',SX, 1'IIRa,6X,'IE' ,SXIaWER8,5X,'WTLI',4X,'PEREX', 3X. 'PERIN') Set tidal volume and respiratory frequency DO 1 J = 1.9 rlr = B(J) RISPBZ = ?(J) Bstablisb time increment DT = 3.00/(BISP82*30,0) Marlmum velocity VIAX = 3.14 * RtSPfiZ * VT Sample flow rate every 12 degrees DO 2 I = 1, 30 Set bench data counter lot2 Convert degrees to radians Z = (3.14/15*0) * I Plow rate RP = SII(Z) * VWAX IF (1-15) 40,40,4S ~stablishexpiratory phase valu2s vr = 2(n) vo = C(M-1) PI = D(N) PO = D(M-1) I (F - I) 50,55,60 Establish inspiratory phase values vx = A (a) vo = A(U-1) PI = B (N) PO = B(N-1) I? (RP - VI) 60,55,50 If flow rate less than bench flow rate, interpolate P = P + RP * (((R - 0)1 - 0 ) * (PI - PO) + PO) * DT GO TO 70 If flow rate aqua1 to bench flow rate, calculate W W=U+BP*PI*DT GO TO 70 If flow rate greater than bench flow rate, increment bench IF (N-30) 65,23,23 1=11+1 GO TO 35 PRITE (6,24) PORIYA!? ('0' , Plow rate exceeds approximation') 60 TO 2 I (1-35) 2,7S,2 FIE = Y/1000. a = 0. COITIEUE I1 = 9/1000. VBITlY = BBSPEZ * VT urn = @I RESPRt WtlY = PE * RESPHZ UTIY = wrH + PEE PEREX = (PEH/WT~) * 100. O PBRII = 100.0 - PEREX 25 WBITE (6,26) VT,RESPHZ, PEITI,UI,UIW.UE,UtM,iiTCI, PEREX,PEBf ll 26 ?ORHAT (SX, 1OF8 -4) a = 0. 1 COIITINUE STOP EllD SBMTEY - 0.00- 19.28- 38.55- 57.83- 77.10- 96.38-115.66-131.93-154.21-173.Y -192. 76-212.04-231. 31-250. 59-269.86-289. 34-308.42-327.69-346.97-366.2 -385.52-r)O9.8O-r)2@ .O7-l)r)3.3Wb62.62-~8I.9O-SOl. [email protected] -1.50 -57.27 -59.39 -59.39 -63.63 -63.63 -63.63 -63.63 -63.63 -63.6 -63.63 -63.63 -63.63 -64.48 -65.75 -68.72 -72.91 -71.24 -78.48 -89.0 -1Ol.8l-llU.S3-l3l.SO-lQ4. 23-161.20-1 74.77-I9O.89-2O7.86-222.7l-239.6 0.00 5.05 10.10 15.15 20.20 25.25 30.30 35-35 40.40 45.4 50eSO 55.55 60.60 65-65 70.70 75.75 80.00 85.85 90.90 95.9 101.00 106.05 111.10 116.15 121.20 126.25 131.30 136.35 141.40 151.5 0.30 1.32 2.84 3.85 5.17 6.39 7.41 8.93 9.94 11.4 12.99 14-21 15-53 17.35 19.08 20.60 22.63 29.15 26.49 27.9 29.94 32.27 34.61 36.84 39.59 42.93 45.98 49.02 53.08 61.2 1.00 1.50 2.00 2.50 3.00 3.00 3.00 3.00 3.00 14.6 17.00 18.20 18.90 19.40 22.00 26.00 30.00 34.00 ~ppendixB Computer Program f9r Resistrvo Work/Dynamlc Tests /*JOBPAR!! PSR D=HAD, PPT?=5 // EXEC PORTGCLG,REGIObl.G0=24OK //PORT.SYSI# DD * set up data arrays for displacement, diff. press., ventilation, total, resistive and hydrostatic work of inspirit ti>n, and total, resistive and hydrostatic work of expiration ODIMBMSIOM (2030), B(2000) ,VEIT (50). H (SO), YI (50) , 1WIR (SO), MI8 (50) .UB (50) ,VER (50) ,uEEi (50) JKI (SO) JKP: (50) ,n (2000) Read R~3r~staticRead Data in cm. H20 A(1) = 0.0 REID(S,11) (fi(1) .I=2,32) PORnAT (8% 2) Read digitized Sisplacement and diff. press. data DO 2 I = 1,1502 READ(5,12)A(I) ,B(I) ,C FOREAT (3 P8.0) tOllT'llOUE Sstablish time increment DT = 1.00/60.00 Surface area 3f piston in sq. cm. SA = 3.14 * (19.79/2.0) ** 2 Displacement transducer cm. conversion factor CALA = 0.0040 ~ifferentialpressure transducer mmH20 c~nversionfact~r CALG = 0.209 Zero Offset Corrected to HUE20 OPFSET = -210.0 Establish demand valve water head in am HZ0 ED = 187.0 Center Volume of Cylinder in Milliliters Lf5710. Equivalent Center Line Voltage El = L/(SA * CALA) Actual Center Line Voltage: (MAX + !lIN)/2 E2 = 619.0 Voltage Correztion E3 = El - E2 C3rrected isp placement D(1) = 2 * E2 - A(1) + E3 PRINT 30 OFORMAT (6X,'TIDVOL1 ,2X,'8ESPHZm ,2X,'VERTl•÷',YX, lUIIY', lSX, 'UIBfl',UX, 'UIBE1,UX, 'OELI',5Xo 'UERH',UX, 'UEHH1,UXo 2'PTl!l',UX, PERE EX',^^, 'PERIN'14X, 'AC') Bstablish lung centroid water hssd in mm 820 DO 3 I = 1,32 HC = B(N) Set expiratian counter equal to zero KE = 0 Set inspiration counter equal to zero KI = 0 Set resistive work of inspiration equal to zero UKIR = 0.0 Set resistive work of expiration equal to zero WKBR = 0.0 Set hydrostatic work of inspiration to zaro OKIB = 0.0 Set hydrostatic uork of sxpiration to zero UKEE = 0.0 Set complete inspiration cycle internal data count to zero UKI = 0 Set complete expiration cycle internal data count to zero BKE = 0 Sat total data count for even inspirations and expirations equal to zero rsun = 0 Set uncorrected minute work of inspirati~nequal to zero Puxn = 0. Set ancorrectad minute resistive work of inspiration equsl to zero PWXRB = 0.0 Set ancorrected minute hydrostatic uork 3f inspiration equal to zero PWIRE = 0.0 Set uncmrectad minate resistive work of expiration equal to zero PUERH = 0.0 Set unssrrected minute hydrostatic work af expiration squal to zcro PWEHH = 0.0 Set uncorrected minute work of axpiration squal to zer~ PWER = 0. Set ventilation equal to zero VEY = 0. PtEllT = 0. DO O I = 2,1402 OD (I) = D (1-1) - ((2*E2 - A (1-1) +E3) * (Bl) CALG+10330, + H 1/ (B (I) * CALG + 10330, + ED) - (2*E2 - A (I) + E3)) 2011TI HOE DO 5 I = 1, 1396 Five point sm~othingcurve variables for relocity AA = D (I) BB = D(1 + 1) CC = D (I + 2) DD = D (I + 3) EB = D(1 + 4) Velocity in cm./sec. using five point smaathing PI = ( (-2.0 * AA - BB + DD + 2.0 * EB) * CALI )/(lo * DT) IF (1-1) 35,35,40 Initial vel~cityin cm. /set. using five point smoothing VO=VI GO TO 5 Carrected flow rate in liters/sec. B? = S1 v1/1000. Cartected differential pressure in mB20 PC = B (X) * CALG - HD - O??SBT Incomplete first cycle rejection I? (RE) 45,45,65 I? (KI) 50,50,65 I? (VO) 60,5,55 IF (VI) 85,5,5 IP (YI) 5,5,100 IP(V0) 70,70,75 IF(V1) 90,90,95 XP(V1) 80,105,105 Positive t3 nogative, (VO positive and Vi negative) Finalize work of expiration for that breath, reset u~rkof expiration, finalize expiration cycle internal data coant, and increnent expiratian coan tar IP(IKB-40) 105,105,82 UBR (RE) = OKER WKlR = 0.0 OBR (KB) = PKEB aB(rtt) = am (KE) + UEH(KE) PKEH = 0.0 NKE = KG JRB (HKB) = NKE VEIIT(KE) = VEN 1IKB = 0 VEU = 0 VO = VI KI = KI + 1 negative no change, (both VO and VI negative) Add vork segment to vork of inspiration for that breath, keep c3anter the same, and increment inspiration cycle internal data count URIB = URlR - RP * PC * DT UKIB = PEIB - EC RF * DT * 19.0 llRI = DRI + 1 GO TO 5 legatire t:, positive, (VO negative and VI positive) linalire uork of inspiration for that breath, reset work of inspiration, finalize inspiration cycle internal data coant, and increment inspiration caunter I?(RRI-&O) 9O,9O, 97 WIR (XI) = IKIR Our8 = 0.0 WIB (KI) = WKIB WI(KI) = Era (KI) + arri (KI) UKIE = 0.0 RKI = KI 3KI (MI) = IKI NKI = O vo = VI KE = RE + 1 Pasitive no change, (both VO 3nd VI positive) Add work segmant to work of expiration for that breath, keep counter the same and increment inspiratian cycle internal data count YKER = wnea - RF * PC * DT PKCR = WKtB - BC * R? * Dl' * 10.0 NKE = IRE + 1 VCN = YEN + R? * DT ZONTIIIUE Calculate smallest number of even complete half cycles IF (EKE-HKI) 110,115,115 J = EKE GO TO 120 J = nur DO 6 I = 1, J rsun = Isou + JKI(I) + JKE(I) Time uncorrected minote work of inspiratim PWIA = PIIIl + OI(I) Time uncorrected ainuta resistive work 3f inspiratim PYIBN = PUIRIl 4 WIR(1) Time uncorrectea minute B ydrosta tic rork of inspirati~n PPIHU = PCTIFill + UIH(1) Tin uncorrected minute work of expirati3n PWBI = PUB8 + RE (I) Tim uncorrected minute resistive uork of expiration PWEPl = PUBRH + PIER(1) time uncorrected minute hydrostatic rork of expiration PQl!E!•÷ = PPBHIl + WBH(1) PfBlT = PIIN? + VEBT(I) COBTI ID I Ainute work of inspiration in kg. m. /.in. PI!•÷= PUIR * 0.06/(ISUWDT) Minute work of resistive inspirathn in kg. a. /.in. PIRH = PWIRU * O.O6/(XSUR*DT) Minute work of hydrostatic inspiration in kg.~./min. APPENDIX (continued) Appendix c Hydrostatic Pressurz i~baianca Subject Data HYDROSTATIC PRESSURE 1 MBALAlYCE SUBJECI' DATA Subject Hoight (cs.) TB 182.9 MC 172.7 2 El 186.1 i) H 162.6 DM 173.1 JFI 1BL.9 NS 181.6 LT 177.8 Hi? 179.7 LW 765.1 Apper;?ix 1; Steady St3t3 Estimations of the Work of ~reathingfor Single Hose and Two Hose Hegula tors, where: VT = Tidal Volume in liters RESPHZ = Respiratory Frequency in breaths/min, VEMTH = Minute Ventilation in lit~rs/mic. WT: = Work c?f Inspiration in kg. ra, /breath AIR = Binuta Hork =tf Inspiratior! in kg. nl. /pain. WE = Uork of Expiration in kg.m./breath UEPI = Minute Uork of Expiration in kg. ra./min. UTM = Total Hinute Work of Breathing in kg.ni./min. PEREX = Expiratory gork Percentage of Total Work of Breathing PERIN = Insplratory Work Percentage of Tot31 Work of Breathing VT RESPHZ BENT# WI. WfH WE!! UTM PEREX PERIN 1.00 14.60 14.60 0.02 0-35 0.11 0.47 24.34 75.66 1.50 17.00 25.50 0.04 0.60 0.26 0.85 29.98 70.02 2.00 18.20 36.40 0-05 0.95 0.47 1.42 33.00 67.00 2.50 18-90 47.25 0.07 1.35 0.73 2.09 35.22 54-78 3.00 19-40 58.20 0.10 1.85 1.08 2.93 36.88 63.12 3.00 22.00 66.00 0.10 2.30 1.38 3.67 37.49 62.51 3.00 26.00 73.00 0.12 3.23 1.94 5.17 37.54 62.46 3.00 30-00 90.00 0.15 4.37 2.63 7.00 37.55 62.45 3.00 34.00102,00 0.17 5.66 3.Y5 9-11 37.92 52.08 POSEIDON WET STATIC DATA WORK OF BREATHING ESTIBATZOBS VT RESPHZ VENTH #I UIH WE WEB WTH PEREX PERIH 7.00 14.60 14.60 0.01 0-07 0.04 0.59 0.6789.00 11.00 1.50 17.00 25.50 0.01 0.21 0.08 1.28 1.48 86.06 73.94 2.00 18-20 35-40 0.02 0.43 0.12 2.15 2.58 83.34 16.56 2.50 18.90 47.25 0.04 0.75 0.17 3.20 3.95 80.94 19.06 3.00 19.40 58.20 0.06 1.21 0.23 4.39 5-59 78-45 21.55 3.00 22.00 66.00 0.07 1.65 0.24 5.30 6.95 76.28 23.72 3.0026.0078.00 0.10 2.51 0.26 6.89 9.3'373.3226.58 3-00 30.00 90.00 0.13 3.76 0.29 8-69 12.45 69.79 30.21 3.00 34.00102.00 0.15 5.41 0.32 10.71 16.72 66.46 33.54 TRIESTE I1 DRY STATIC DATA VORK OF BREATHING ESTIBATIONS VI' RESPHZ VENTH YI YIf5 BE BEN UTX PEBEX PERIN 1.00 14.60 14.60 0.06 0.84 0.01 0.13 0.97 13.62 86.38 1-50 17oOO 25.50 0.09 1.55 0.03 0.43 1-98 21-67 78-33 2.00 18-20 36-40 0.13 2-28 0-05 0.97 3-24 29-84 70.16 2-50 18.90 47.25 0.16 2-97 OelO 1.92 4.89 39.28 60.72 3.00 19.40 58.20 flow rate exceeds approxiaation TRIESTE I1 RET STATIC DATA WORK Of BREATHIHG ESTIHATIONS BT RESPHZ VENTfl BI Urn YE BEH UTR PEREX PEBIA 1.00 14.6014.60 0.04 0-62 0.01 0.12 0.74 15.9084.10 1.50 17.00 25.50 0.06 1.05 0.02 0.38 1.43 26.53 73.47 2.00 18.20 36.40 0.08 1.48 0.05 0-85 2.33 36.5563.45 2.50 18.90 47.25 0-10 1.87 0.08 1-52 3-39 44.77 55.23 3.00 19.40 58.20 0.12 2.26 0.13 2-47 4,73 52. 17 47-83 3.0022.0066.00 0.11 2-52 0.15 3.31 5.83 56,7343.23 3.00 26.00 78.00 0.11 2.93 0.19 5-00 7.93 63.04 36.96 3.00 30.00 90.00 0.11 3.43 0.25 7-40 10-83 58-34 31-66 3-00 34,00102.00 0.13 4.31 0.32 10.99 15.29 71.84 28,16 Appandtx E Poseidon Single Hose Dynauiic Work of Breathing Calculations including fnspiratory and Expirat~~yWork Variations with Chacges in Diver orientation, where: TIDVOL = Tidal Volume in liters RESPHZ = Respiratory Frzquency in breaths/min, VENTE = flinute Ventilation in li ts rs/min. wf8 = flinuts aork of Inspiration in kg.m./min. WIRR = Hinute Inspiratory Resistive work in kg, n, /inin. VIHH = flinute Inspiratory Hydrostatic Hork in kq.a./min. ME!! = Hinute Bork of Expiration in kg. m. /@in. @ERR = flinute Expiratory ResFstivs Work in kg. m, /win. WEHB = Minute Expiratory liydrosta tic work in kg. n. /%in. YTB = Total Minute Work of Breathing in kg,m,/min. PEREX = Expiratory Work Percentage of Tot31 Vork of Breathing PERIN = Inspiratory Work Percentage of Total Work of Breathing HC = Hydrostatic Prsssure Iinbalance in cm. TWQL IE~Zvent* WI* WIRW wrnr urm umm -)(Y WTM PEREX nrrw nc 043 090 73 0 -65 0.65 0 03 0.42 a42 00 1 008 1.43 8 090 12.73 -4.23 -4-88 5.35 0 042 4.93 4 8-90 12-73 -4034 0.65 -4.99 5-46 Om42 5.01 143 8-00 12.73 -4.39 0.65 -5.04 5.51 0.42 9.09 043 90 12-73 -4.38 0.65 -5.03 051 042 1 .*3 8.00 12.73 -4.32 0-65 -4.07 5.4s 0.42 t 8.90 23 -4.21 0.65 486 5-33 0.42 am43 8-90 12.73 -4.04 O14b -4.60 6 0142 + em -7 0.65 a044 Q-42 8-00 12.73 -3.59 0.65 -4.20 4r6T 0.42 4-25 1-43 8o.O 12-73 -3.24 0-63 -3.80 43 0.42 3-9s 1 .I1 390.74 -f.9.T@ 14 6-90 12.73 -2.80 0.65 3 1-99 042 3.S7 1.11 359.- - b9,U 53:s -43 098 073 -2.49 6s -3.14 eS9 042 0.17 011 - 076 r26mm . 4 8-00 12-73 -2.06 0.65 -2.71 3.16 0.42 2.74 Irl-0 a840.b - 1-43 8-90 120t3 -1.60 0.65 -245 2.70 0-42 2.27 1.10 -5-81 -1U.Sl -1T.U 1.43 8.90 12.73 -I.II 0.6s -1 077 2.21 o 042 1-70 r .ee ror .ot -lor at 4 - 6090 12-73 t0.64 0.65 -1rZll 1 070 0.42 1.27 010 46. a -0 - 0-75 1 000 rm -8r it% kg tfS3 8% -8.3: k Et2 0.22 LIOI 40.08 -1.- 13 8-00 12.73 0.96. 0.15 0.3 1 0.81 0.42 -0~31 1.07 I..#10.41 W-SV a*** 04s -90 73 1-48 065 0.83 1 &S 80.9 12~73 2.00 0.65 1.W -0.94 Or42 -1.36 ' &rat 81- 12-73 2050 0-65 9 -1.44 042 -1d7 r. a 1dS 8r.O 12.7,3 2-90 0.65 2.33 -1093 1 73 3.43 attr 3-86 ads - 6 12 S 4r;N 0.65 4 -3&1 O4t *3-63 144-308.3* 4QI.24 20.83 --t &**l .*SO I 6 0.65 34s r-kb4 0.42 -SOW 144-34.1.- 443L.30 -90 06s 4 02s 42 -16 OI 41 0.4 -4rS6 1 I0 S -400011 L7 '3.2 kt': -4.34 0.2 -4.77 141 -421.96 S21.n 3TA - 1- 8- 12.73 3 0-6s 4.88 4 0.42 -4.93 1.03-438.71) b38.20 38-72 T:DUW RLSPWZ VCNTY VIM r 1Rn rl I~Y WCY wmr wcnr rtw PEREX PERIN MC 1-49 14-79 22-05 1-16 1.13 0 00 0-74 0.74 0-0 1-02 34-56 a-w I+-79 zit.0~ -7-27 rela -a -45 9-28 o -74 8-54 2-01 461 -66 -3 1-40 14-19 22-05 -7.45 1 16 -8 064 9-41 0174 8-72 2-01 470-32 -370032 ,-a9056 1-40 14-79 22eG5 -7-54 1-16 -8-72 9-55 0 074 8.8 1 2-01 474.50 -3N.60 -39.96 1.49 14-79 22.05 -7.53 1-18 -8.71 9-54 0-74 0.80 2-01 47bOO -374000 -39-92 1 a49 Im-79 22-05 -7.43 1 18 -8-61 9 44 0 -74 70 2-08 469-18 -36001. -39.45 1-49 84-79 22-05 -7-23 1-18 -8041 9-24 0-74 8-90 2-01 4S9-67 -SSSd? -38.54 1-49 14-79 22-05 -6.94 1-18 8 8-95 0-74 8-91 2-01 445074 -34kt4 -37oZL 1-49 14-79 12-03 -6.56 1 18 -7-74 8-57 0174 7-82 2-00 427. - 0 - 4 a -4s I.-T~ zr- o 5 -6.10 1.1a 8-10 9-74 7.3s - -0 1-40 14-79 22-05 -5-55 1-18 -6.74 7-55 0 -74 6-81 f:E dk!!& -2%- 1-49 14-79 22-05 -4.94 1-18 -6-12 6-92 0-74 6- 18 1-99 3*.-45 -24004s -28.03 8-49 14-79, 22-05 -4-25 1-18 -5-44 6-23 0-74 5-49 1-98 314.82 -214.82 -24-90 1-49 14-79 22'-05 -3-31 1- I8 -4.69 5-68 0-74 4- 74 1-97 277-91 -1TlrVl -21.49 1-49 *a-79 21-05 -2-71 1-18 -3-89 4-6b 0-74 3-93 1-96 238.08 -1 1+49 14-79 22eG5 -1-88 1-18 -3-06 3-83 - 0074 3-09 1-96 195093 : 1-49 14-79 22-05 -1-00 1- I8 -2-19 2-95 0-74 2-21 1-95 151-52 - 49 14-7s c+OS -0.11 1-le -I 2-0s 0 -74 1-30 1-94 10s-57 1-40 11-79 22-05 0-80 4-18 -0-38 1-13 0174 0-38' 1-93 58-30 41-63 -1-re lo49 14-?9 22005 1-7 1 1-18 0-53 0020 0-74 -0.54 1-92 10-63 a*-37 2 44 1-49, t*o?9 22. 0 5 2-62 be 18 1-44 -0-71 0-74 -1 -44 1-91 -31-S6 137036 8-60 3-52 1-18 -0 - 1-90 -8SrOO 1.5000 10.60 t::;. ft:3 :::z 4-36 1-18 : - Ex -325 1-89 -1 31 -68 14-66 1 14.79 21-05 5-21 1-16 4-03 -3-33 0-74 -4-07 1-88 -176-89 %%:% 18-47 Or9a A4179 25-05 6-00 1-18 4-82 -4-12 0-74 -4-67 1-87 -219099 319.99 22-07 EWlP 54-79 22-05 6-74 1-18 5-35 -em87 0.74 -Soel 1-07 -260-67 3e00.7 25-U &rlW 14.79 22-05 7-41 1- 18 6-23 -5-55 0-74 -6-29 1-86 -298.27 398oa7 280S3 &-*U l4.tO 22.05 8-01 1-18 6-63 -6-16 0-74 -6-90 1-85 -332020 r 432020 31-SO ad0 14-79 22-05 8-54 1-18 76 -6-70 0-74 -7-44 1-65 -362.16 1-49 14-19 22-05 8-09 1. I8 r-8 1 - 5 0 -74 -7.09 1-04 -3S7-69 L0e9 14.79 22-05 9.36 1-la 6-18 -7-52 0.74 -em26 1-84 -408.49 506049 37-46 1-49 14-19 22-05 9-63 1- la 6-45 -7-80 0-74 -8-54 1-84 -424.23 524.23 38.72 PIL~run c*uro.oraa cr~clo.rt4oc+ur=-?s.7 nolroo.o ta-037.0 I ~pp?cdixF Trioste 11 Two Hos.3 Dynamic Hork of Breathing Calculations including Inspiratory and Expiratory dork Variations with Changas in Divar Orientation, whers: TIDVOL = Tidal Volume in liters RESPHZ = Respiratory Frequency in b rsa ths/rnin. VENTB = ninute Ventilation in li te rs/min. UIH = Minute work of Inspiration in kg,m,/min. RIRH = ninute Inspiratory Resistive Work in kg. m. /&in. WfH3 = Minute Inspiratory Hydrostatic Work in kg. in. /min. BEPI = Minute nork of Expiration in kg.m. /mine WERH = Hinute Expiratory Resistive Uork in kg.m,/min. WEHH = Hinute Expiratory Hydrostatic nork in kg. m. /min. BT&l = Total Minute work of Breathing in kg. m. /ain. PEREX = Expiratory work Percentage of Total Work of Breathirig PERIN = Inspiratory Work Percentage of Total Work of Breathing HC = Hydrostatic Pressura Inbalance in cm. ICNTU u11 u IRW wtnm UEW WERY row u YM PEREX PERIN nc LP.06 n-77 n-77 o -3 1.~10 I -00 0-0 1-77 6.46 430.~4 00 10.96 -1.73 C.77 -2.50 3 054 1.00 2.54 1.81 19S.59 -95.59 -23.18 10.96 -1.54 0.77 -2.31 3.35 1 000 2.35 1-81 185.29 -85.29 -21.43 L0.96 -1 033 0.77 -2.10 3.13 1-00 2.13 1.80 173.60 -73.60 -19.45 LO. 96 -1 -09 0.77 ~1.96 2.89 1 .GO 1_._ee 1-60 160.56 -60.56 -17.25 10.96 -0.83 0.77 -1 055 2.63 1.00 1.63 1-80 146.34 -46.34 -Lb.Bb-- 0.96 -0.56 0.77 -1.33 2.35 1000 1.35 1.79 131.15 -31.15 -12.32 10.96 -0.27 0.77 -1 034 2.0: 1.00 1.06 1.79 114.99 -14.99 -9.63 10.96 0.03 0.77 -Go74 1.7, 1 *bO G.7s 1-78 98.14 086 -6 084 0.96 j.34 3-77 -0 043 1.44 1.00 0.44 1-78 80.78 19.22 -3.91 .Oo 96 0.66 0.77 -0.12 1.12 1.00 0.12 1.77 63-02 36-96 -1.07 0.96 0.97 0.77 0 -2 0 0.80 1.00 -0.20 1.77 45.10 54090 1-05 1.98 0.77 5 &-0 ~O-.~1.76 27.20 7201 407s 5-96 1-50 0.77 6-62 0. 17 1.00 -0.63 1-76 9 $2 90.4t -7iSir 0-96 1 oB9 0.77 1.12 -0.14 1.00 -1.14 1-75 -7.69 101.69 10.36 ,0096 2.le 0. 77 lob0 -0.43 1.00 -1.41 1-75 -24.31 124.31 13.01 96 204a 0 77 1-58 -0.7C 8-00 -1.76 1.75 -40.12 140. 96 2.70 0.77 1.93 -0 96 1.00 -1.96 1.74 -54.93 154. ,0096 2.93 0 -77 2.16 -1.19 1.00 -20 19 1.74 -66.53 16a.53 20.00 10- 96 3.14 0.77 2.37 -1040 1100 -2.40 7 -60.79 laom79 21.92 ,0. 96 3.32 0 77 2.56 -1.60 1-00 -2.59 1.73 -91.61 191.61 23.61 ,O. 96 3.47 0 77 2.70 --f-~6O--~-T.f;C~1.73-100.73 200.73 25-03 *0 2s ii 31-90 $10. :::43 &20. -16 10*2 It; '181 27. 45 27. 020 It. 008 a70 021 2*. rJ3 25 -11 24. .IS 23. '9 14.56 3-65 to. 14.18 3 a65 10. tP 13-66 3-69 10.