REPORT NO. NADC-89009.60

AD-A210 123

EVALUATION OF THERMAL STRESS INDUCED BYHELICOPTER AIRCREW CHEMICAL, BIOLOGICAL,

RADIOLOGICAL (CBR) PROTECTIVE ENSEMBLE

Jonathan Kaufman, Katherine Dejneka, Stephen MorrisseyAir Vehicle and Crew Systems Technology Department (Code 6023)

NAVAL AIR DEVELOPMENT CENTERWarminster, PA 18974-5000

D T IC Alvah Bittner, Jr.

S ELECTE _ BATTELLE, HARC

JUL 17 1983 Seattle, WA 98105-5423

15 JUNE 1988

FINAL REPORTPeriod Covering 3 November 1987 to 17 December 1987

Task No. 85310001Project No. A531531A0015

Work Unit No. CLO-202Program Element No. 62462N

Approved for Public Release; Distribution is Unlimited

'x•j-C'~i&'-/2L' ~Prepared for

NAVAL AIR SYSTEMS COMMAND' (AIR-5311)Department of the NavyWashington, DC 20361

NOTICES

REPORT NUMBERING SYSTEM - The numbering of technical project reports issued by the NavalAir Development Center is arranged for specific Identification purposes. Each numberconsists of the Center acronym, the calendar year in which the number was assigned, thesequence number of the report within the specific calendar year. and the official 2-digitcorrespondence code of the Command Officer or the Functional Department responsible forthe report. For example: Report No. NADC 88020-60 Indicates the twentieth Center report forthe year 1988 and prepared by the Air Vehicle and Crew Systems Technology Department. Thenumerical codes are as follows:

CODE OFFICE OR DEPARTMENT

00 Commander, Naval Air Development Center

01 Technical Director, Naval Air Development Center05 Computer Department

10 AntiSubmarino Warfare Systems Department

20 Tactical Air Systems Department

30 Warfare Systems Analysis Department40 Communication Navigation Technology Department

so Mission Avionics Technology Department

60 Air Vehicle A Crew Systems Technology Department

70 Systems & Software Technology Department

80 Engineering Siqpport Group

90 Test & Evaluation Group

PRODUCT ENDORSEMENT - The discussion or instructions concerning commercial productsherein do not constitute an endorsement by the Government nor do they convey or imply thelicense or right to use such products.

APPROVED BY: DATE:

W. F. MORONE\.

CAP', 'S,(., L'.3- NAV\Y

4t

Unclassified

REPORT DOC IUMENTATION PAGE Fj~orm 88foe

la REPOR' SECjR TY' CASS:F;CA-iONr 10 RESTRICTIVE VARKcNGS

Unclassrfied'a SECjR.'- CLASS * CA- Cý',.,-7,03?0STR.E.;.7QN A.A ,A8-TY 0 ;

2b DCLA~icCA'~N D~N~A0'; SCED~Approved for Plublic Release:2b DCLASIFA~iO DOvNGWCY%- SC D-EDistribution is UNlimited

4 PERFORMT.,G ORGA%.Z4,O% REPORT Nu~t3ERS, 5 MONITORING ORGAN.ZATON REPOR- NN'BERS

NAlC-89009-60

6a NAVE OF PE R4OR7V ORGA'. ZA' O% bD 0, CE S VbQ 3C, a NAME OF MON 7OR %Cj ORGAN A- 0N

Air Vehicle and Crew Systems OfI dpiicable)Technology Department I 6023

6c ADDRESS (City State. and ZIP Code) 7o ADDRESS (City. State and ZIP Code)

NAVAL AJR DEVELOPMENT CENTERWarminster, PA 18974-5000

Ela NAV! 0i ; DN SPONSOR BD 0o ; C; ~b 9 PPOCiPE'VENW iNj'R-E.A'E DEN- CA'~i. NORCANZA-ON j (if adpl.Cable)NAVAL AIR SYSTEMS COMMAND j AIR-531 1

8c ADDRESS (City. State, and ZIP Code) r soA1cE OF CND'N!CN.'*-PROrGRA,. "~,C 'AlljPDepartmrent of tte Navy fELEMllE NT NO NO 12OjCCSO N

Washington. DC 20360 62462,N 'A531531A- 853100001 CLO0202S10015

11 TITE (includeC Security Coassfiaor,,n

(U) Evaluation of Thermal Stress Induced by H~elicopter Aircrew Chemic". eidloical, Radiological (CORl Protectiv Ensemble

12 PERSONA, ALJTm.ORIS)

J. W. Kautman*. K. Y. Deineka*¶ S Morrissey", and A Biltner, Jr13a TYPE 0; REPORT 3C I'VE CU.EF:iJ 4 DATE 0; REFOR7 (Year.Mumh 0j)) Od 5~A

F'inal rROMo 11/3/87 TO 12/17/88 1988 June 15 2916 SuPP.EMEN7ARY NOTATION

*NAVAIROEVCEN *ANAL'fTICS, Inc., Willow Grove, PA 1 909

COS4., CODES IS S4SJECT TERMS (Continue 01 reverso of necessary and *denlfi4 by block nui,5'l1`,D G~j ý, P, Hyvethermia Physinolgy

06 10 Chemical Warfare IS01t111111Hest Tolerance

19 A85-RAC' (Contsnje on toiverse it necessafy and identify by block 1,uImiOCV

* LN!T-RP!!CTQ The Ao`22P-9(Vj Chemical. Biological. Radiological (CBRI Protecive Assembly for helicopter arpews has beenevaluated for the additional theimal stress it Imports to users in a holl eonwonment The standard airoew flfe kv~pwv system forhelicopters. based on thew CWU-27/P flight coverall, was employed as the experimente control. METMQQ5. Two environmentaconditions wero studied: 1) a simulated hot woraft inlqiow (holl. with ciwtoer temperatume maintaineod at dry bulb teWratures (Tdb

=32.8 -±0.1 "C; and a wet bulb, temprnature (T.0) - 25 0 t 0-50C. and 2) a oontlol environment Irmol). with chamber temperaturesimantained at Tdb - 20.q 0 11C and Toot - 15.0 t 0.5C.)Three males, aged 24-35 years. were exposed twice to each

garment/envwronment conditidri cmbneition. #wr a total of eight exposures each,' except for one subtect whio was studied in ooconditions only once in each of toa configurations. for a total of cix runs. Teat duratios were designed for 480 miwnue RE$V&T$Comparison by ensemble show Significant diffeences lp<0 050 observed lor exposure durations. while rectal temroeraturpt %weesaginifcan~tly ddfferent (0<005) between eonselbles only in hot conditions. Ambient conoditions signicNmor*1 ripeled on nearty almeasured parameters, r~qCAj-WQ The results indicate that the CBR ensoemble repejwents a wnitin factor. in perfrmance in ahot enwonment.

20 0 STR RUTION AVA;,AB;LITY OF A8STRAC' 21 ABSTRALT SECURITY CLASS4IcATiO%

0 JNCLASS19 ED UNLIV"E C SAVE AS PC- Q i'ir r juju¶ as nclasaffied22& NAV' 01 Pi iPONS B.E IND ý'A '20

TELE'iOE lp~ciudo Arooi (0dal) U,('I

Jonathan Kaufman (25 42565 6023

DID Form 1473. JUN 86 Prveaoui ood,bcOins are obsofete- AS

SIN 0102-LF-014-660O3

SECURIih CLASSI~CATIC)% CQ THiSI PAGE

DD Form 1473. JUN 86 ~s r~u

NADC-89009-60CONTENTh

TA BLES ............................................................. iv

FIG URES ........................................................... iv

INTRODUCTION ......... ................................ 1

MATERIALS AND METHODS ............ 1SUBJECTS .. ........................................ 1MATERIALS ........ ................................ 1METHODS AND PROCEDURES .......................... 2TEST PROCEDURES .. ................................. 2COGNITIVE AND PSYCHOMOTOR TESTS ................. .4PHYSIOLOGICAL INDICIES ............................ 4STATISTICAL ANALYSIS .............................. 5

RESULTS ........................... 5VOLUNTARY DURATION TIME .......................... 5RECTAL TEMPERATURE ............................... 5HEART RATE ....................................... 6MEAN SKIN TEMPERATURE ............................. 6THERMAL GRADIENTS ................................ 6HEAT STORAGE . ..................................... 6SWEAT RATE .. ...................................... 6COGNITIVE AND PSYCHOMOTOR DATA ................... 7SUBJECTIVE RESPONSES ............................... 7

DISCUSSION ................... .......................... 7

CONCLUS .IONS ........................................... 10

ACKNOWLEDGEMENTS ......................................... 11

REFERENCES ............................................ ..11.

TI3

j tII

Dt t-j1'

NADC-89009-60TABLES

Table Eg

1 Physical Characteristics of Subjects ....................... 132 Clothing Configurations .................................... 133 Mean Values, Duration, Tre, Tsk, and S ..................... 144 Mean Values, Urine Specific Gravity, Water Consumption,

Total Sweat Rate, % Sweat Evaporation, Body Weight Change,and % Total Body Weight Change ............................. 15

5 Mean values, Baddeley reasoning and vertical addition ...... 156 Mean rates of change, subjective criteria .................. 16

FIGURES

FiF-ure Pg

1 A/P22P-9(V) Chemical, Biological, Radiological ProtectiveAssembly .. ......... ....................... ................ 17

2 Environment, Suit, and Trial Effects on Voluntary ExposureDurations . ................................................. 18

3 Environment and Trial Effects on Mean-Rectal Temperature .. 194 Environment Induced Changes in Rectal Temperature ......... 205 Rectal Temperature vs. Time, By Configurations ............ 216 Mean Skin Temperature vs. Time, By Configurations ......... 22

iv

NADC-89009-60INTRODUCTION

The use of chemical weapons in modern warfare has alerted the Navy tothe need to provide adequate chemical protection for its aircrewsthroughout all stages of a mission. This has proven to be a daunting task,however, because of the thermal burden such systems have placed on users inthe past. Designs for garments intended for in-flight use have proven to becumbersome, reduce dexterity, and evoke thermal stress after a short timein use (6,14).

The development of the A/P22P-9(V) Chemical, Biological, RadiolcgicalProtective Assembly (CBR) was believed to have ameliorated a number ofthese problems. This system combines an impermeable ventilated mask(modified United Kingdom MoD AR-5 respirator) with a semipermeablecharcoal-impregnated undergarment (USAF MK-I). With the decrease in bulkcompared with earlier ensembles along with ventilation of the head and neckand a semipermeable undergarment, the CBR ensemble is intended to permituse for extended periods..

The, purpose of this study was to evaluate the thermal load imposed onusers of this system under hot and humid conditions and, if possible,quantify decrements in mission-related cognitive and psychomotorperformance. This study attempted to simulate conditions which might beexperienced within a helicopter during military operations (11,19). Trialdurations of up to eight hours were used to simulate the sustainedoperations anticipated in a wartime situation.

MATERIALS AND METHODS

Three males (Table 1) volunteered to participate in the testing oftwo equipment configurations, both tested under hot and cool conditions fora total of four test conditions, after being fully informed of the detailsof the experimental protocol and associated risks.

SUBJECTS: Weight was recorded prior to each test run. Body surface area(BSA) was calculated (5) from the mean weight and height of each subject.Percent body fat was determined from estimates of body density (4), whichwere computed from skinfold measurements obtained with Lange SkinfoldCalipers (CambrifJge Scientific Inc., Cambridge, MD) and the equation ofLohman (17).

MATERIALS: Two ensembles were employed in this study: 1) the Aviation LifeSupport System (ALSS); and 2) the A/P22P-9(V) Chemical, Biological,Radiological (CBR) Protective Assembly. A list of the individual clothingitems which comprise each ensemble is given in Table 2. While cottonundergarments a.e not standard items in the ALSS configuration, they wereincluded in this study in order to minimize the number of variables.

Cotton undergarments and glove liners are intended to reduce skinirritation and to minimize the contamination of the chemical liner byperspiration. The chemical liner is a liquid-repelent garment coated on theinner surface with activated charcoal. Polyethelyne socks and butyl glovesare intended to provide chemical agent-impermeable barriers at theextremities. The MCK-3/P mask, CQK-2/P ventilator, and A/P37S-l intercom,

NADC-89009-60comprising the above-the-neck portion of the A/P22P-9(V) assembly, providehead, eye, and respiratory protection for users. A bromo-butyl hoodencloses these items and covers the head and neck regions, extending pastthe neck to provide a seal against agent penetration. This hood is intendedto be worn below the helmet.

Two items were not worn by subjects in this study: disposablefootware covers and aircrewman's cape. These items are intended for use byaircrews enroute from a shelter to the aircraft and are to be discardedprior to entering the aircraft. Since they will contribute very little tothe heat stress experienced by aircrews, the items were not Included in theensembles studied.

METHODS AND PROCEDURES: All tests were begun in the morning, and wereintended to last up to eight hours. Each test simultaneously exposed twosubjects to the experimental conditions, with subject pairings randomized.It was intended that each subject use each test garment in both hot andcool. conditions. These exposures were to be repeated, resulting in eachsubject having a total of eight exposures. Two subjects successfullycompleted all eight runs. Due to lower back pain, one of the subjects wasstudied in cool conditions only once in each of the configurations, for atotal of six runs.

Acclimatization, i.e., the physiological adaptation to environmentalstress, provides a greater capacity for individuals to tolerate heatstress. Since it was not possible to fully acclimatize subjects prior tothe start of testing and it would be difficult to compare the results fromsubjects with varying degrees of acclimatization, minimizingacclimatization appeared to assure the oest data. In addition, the resultswould represent a worst case situation, somewhat akin to a unit being movedfrom a cool environment to the tropics. Testing was performed in Novemberand December, with a minimum time interval between any tests for a givensubject of two days, so that acclimatization effects could be minimized.

Test Procedures: Subjects reported to the laboratory on the morning of atest and were given physical examinations by the attending flight surgeon.After voiding, a urinalysis was performed, a blood sample was obtained fromthe antecubital vein for the determination of hemoglobin content (AmesSeralyzer, Elkhart, Ind. , model 5110A) and hematocrit, and each subjuct'sbaseline weight was obtained on a scale accurate to ± lOg (Scalm-Tronix,Wheaton, IL, model 6006SP). Heat flux/temperature transducers were attachedto the following body sites: (A) forehead; (B) left upper chest; (C) leftdistal upper arm; (D) dorsum of left hand; (E) right anterior thigh; (F)left posterior thigh; (G) right shin; (H) right foot; (J) right proximalupper arm; and (K) left lower back. These transducers consisted of athermopile heat flux transducer with a thermistor located in the center(Hamburg Associates, Jupiter, FL). Analog signals from the heatflux/thermistor transducers were amplified (Biolnstrumentation Assoc. , SanDiego, CA, model HF-12/Temp-14) and stored in the laboratory's computer(HMB MSLI-Micro 1123, Orange, CA) for later analysis. A rectal thermocouple(Sensortek, Clifton, NJ, model RET-l) was inserted 8-10 cm anterior to theanal sphincter and ECG electrodes were placed on subjects at this time.

2

NADC-89009-60Subjects were then dressed in the appropriate equipment

configuration, i.e., the standard aircrew life support system assembly forhelicopters (ALSS) or CBR, for that run (Table 2). On the external suitsurface of both garments, type T thermocouples were placed on sitescorresponding to the location of the heat flux/thermistor transducers.Thermocouple voltages were converted to a ± 5 V analog signal (TC.4isolated signal conditioners, Bendec, Santa Ana, CA) and stored in thelaboratory's computer. Upon completion of dressing, subjects were weighed,followed by a rest period of 20 minutes which enabled temperature and heartrate (HP.) to return to a resting condition before commencing that day'strial. The laboratory temperature was maintained at approximately 20*C(68°F) to minimize thermal stress during dressing.

Following the conclusion of the rest period, subjects entered thechamber. Hot conditions for these tests were Tair - 33oC with a relativehumidity (RH) of 70%, while cool conditions were Tair - 21°C and RH - 40%.Runs consisted of an initial 60 minute rest period upon entry into thechamber followed by a repeated cycle of: a) 7 minutes of subjectiveassessment of physiological condition, cognitive testing, i.e., Baddeleyreasoning and vertical addition of 3 two digit numbers, and rest; b) 7minutes of psychomotor testing, i.e., play three rounds on a video game(Atari Jet-Fighter); c) 7 minutes of physical exercise, i.e., 30 W of workon a bicycle ergometer (Bosch GmbH, Berlin, Germany, model ERG 551). This21 minute cycle was repeated until termination of a given run. Individualswere requested to remain in the chamber for eight hours, unless their runwas terminated early due to a rectal temperature (Tre) exceeding 39°C, arate of Tre increase of 0.6C/5 minute period, HR exceeding 90% of themaximum predicted for age, or the subject, flight surgeon, or principalinvestigator requesting termination.

During the first 120 minutes in the chamber subjects had adcess to 2liters of water in their canteen: After this time the canteen was removedfrom the chamber and no further drinking was permitted. This regimen wasestablished tn correspond to the concern of possible contamination bychemical agents due to drinking straw insertion into the mask, thereforeindividuals would probably have only potable drinking water for the periodprior to the actual start of a mission (e.g., time in the ready room,etc.).

Subjective sensations were evaluated by means of scales for fatigue,skin wetness, temperature, and comfort. Subjects were instructed to place amark along a 112mm lIne indicating their subjective feeling for each of thescales. Extremes were indicated on each line by such terms as "extremelyenergetic", i.e., the most pleasant, on the left, versus "extremelyexhausted", i.e., the least pleasant, on the right. Given values were themarked distance from the left origin in millimeters and the rate of changeof the distance determined from the final and initial values. The rateswere obtained from:

(1) Rate - (Vf - Vp)/t (mm/min.)

where V - the final reported value for a given category, V - the valueobtained prior to dressing, and t - the time elapsed when tJe final valuewas obtained.

3

NADC-89009-60Cognitive and Psychomotor Tests: Changes in cognitive performance wereevaluated with tests of vertical addition and the Baddeley reasoning test(2,3). Vertical addition required subjects to sum as many columns of three2-digit numbers as possible in 90 seconds. The Baddeley reasoning test wasa true/false test, with questions in the form of:

"Trut or False A follows B B:A" (2).

This test'was constructed of 31 questions/page, and subjects were permitted90 seconds in which to answer as many as possible. Results from thevertical addition and Baddeley reasoning tests were recorded by both thetotal number attempted and those answered correztly. If suojects completedall 31 questions in less than 90 seconds, the time required for completionwas recorded, with analysis based on extrapolation to 90 seconds for 'boththe number of correct and completed questions. Both the subjectivesensation evaluations and the cognitive function tasks were administeredprior to dressing, every 30 minutes during testing, and after the subjectshad completed the post-test physical examination.

Physiological Indices: Mean weighted skin temperature (Tsk) wascalculated using the equation:

(2) Tsk - O.I(TA) + O.1 2 5 (TB+TK) + O.0 7 (Tj+TC) + 0.06(TD)+ 0.1 2 5 (TE) + 0.15(TG) + O. 1 2 5 (TE+TF)/ 2

+ 0.05(TH) (OC)

where T, are the measured skin temperatures at locations i - A - K (13).Mean weighted skin surface heat flux (HF), i.e., the amount.of energycrossing the skin surface, was calculated from the equation:

(3) HF - O.l(HFA) + 0.1 2 5(HFB+HFK) + 0,O7(HFj+HFC) + O.06(HFD)+ 0.125(HFE) + O.lS(HFG) + O.125(HFE+HFF)/ 2 2 )+ O.05(HFH) (W/m

where HF are the measured heat fluxes at locations i - A • K (13). Therate of heat storage, i.e., the quantity of heat retained in the body, wasdetermined from:

(4) S - (LTre/At)(60 x 0.97 x Mb)/3SA (W/ml)

where ATre is the change in Tre over the test period ('C), At is theduration of the test period (minutes), 60 is a conversion factor from hoursto minutes, 0.97 represents the specific heat of body tissue (W x hr/kg x"C), Mb is the lean body mass, and BSA is the body surface are& (9).

Total sweat rate (m..) was deterrined by the difference between thepost-test nude weight, corrected for fluid and food intake, and the pre-test weight from:

(5) msw - (NW2 - NWI)/At/BSA

where NW is nude weight and 1 & 2 signify pre- and post-test valuesrespectively. In one instance, a subjec. had the need to urinate during arun. The urine was collected and weighed, with the post-test wei6ht

4

NADC-89009-60corrected for the urine weight. The change in garment weight (AGW) due tothe uptake of sweat was determined by:

(6) AGW - (CW2-NW2) - (CWI-NWl)

where CW is clothed weight. The percentage of sweat evaporated (%E) wascalculated from:

(7) %E - (maw - AGW)/msw (%).

Statistical Analysis: Data for the individual dependent variables wasanalyzed using repeated measures analysis of variance (ANOVA). Analyses ofsignificant changes within runs were also performed with paired-sample t-tests. Differences were considered significant at the level of p<O.05.

RESULTS

The results of this study indicate that the CBR configurationproduced increased heat stress when worn in a het versus cool environmentor when compared with the ALSS configuration in either environment.Environment and subject variations were other variables which provedsignificant in the physiological differences observed between runs.Repeated exposure to the conditions appeared to affect cool trial results,though results of the hot trials were unaffected by repetition. The meandata for the dependent variables of voluntary duration time, Tre, Tsk, andS are given in Table 3 with Tre and Tsk plotted in Figures 5 and 6. Meandata for initial urine specific gravity, total'water consumption, totalweight loss, %E, msw, and % body weight lost are reported in Table 4.

Voluntary Duration Tire: Because of the great variance in the length oftime subjects would stay in the various conditions, the exposure durationtime data was transformed using natural logarithms. Results of the ANOVAshow pronounced differences in exposure duration times between the hot andcool conditions (p < 0.01), between equipment er-embles (p < 0.01),subjects (p < 0.01), and to some extent, between replications (p < 0.05).

The temperature of the-environment, i.e., hot or cool, was found tobe a significant main factor (p < 0.01), with subjects having asignificantly lower tolerance time in the hot conditions regardless ofequipment ensemble. The effect of equipment ensemble was highly significant(p < 0.01), with use of the ALSS configuration resulting in longerdurations for subjects ir. all conditions (Table g). There was a significanttriple order interaction between clothing type, replication, andtemperature, which is apparent in Figure 2.

Rectal Temperature: Pooled' data was plotted in Figures 3 and 4 and showsthat: 1) Final Tre is much higher in the hot conditions than in the cool,conditions; 2) Increases in T over the time of the study are greater inthe hot environment than in tKe cool environment; and 3) Use of the CBRsuit resulted in higher Tre's in all conditions when compared with the ALSSat the same time (Figure 9). In addition, T 's resulting from use of theCBR Ensemble in the hot condition were signflicantly greater than the ALSSthroughout the course of trials (p < 0.05) (Figure 5). Differences betweenTre's obiserved foi- CBR trials in the hot and cool conditions were found to

5

NADC-o9009-60

be significant from minute 121 through the end of the trials (p < 0.05).The ANOVA revealed that across equipment ensembles, Tr was significantlyhigher in the hot environment than in the cool (p < 0. 1), and there was asignificantly greater change in (Final Tre - Initial Tre) in the hotenvironments (p < 0.01) There was a significant interaction between thereplication and hot environments (p < 0.04). These interactions are shownin Figure 3.

Heart Rate: Comparisons of final HR's indicate that significant differencesexisted between ALSScool and the hot ALSS and CBR runs. No other final HRdifferences were significant. Only initial HR differences between the cooland hot ALSS runs were found to be different, though even this differencewas 'of'questionable physiological importance. Mean values for HR are givenin Table 3.

Mean Skin Temperature: Behavior of Tsk is given in Table 3 and plotted inFigure 6. This data shows a response pattern similar to that of Tre, i.e.,a higher Tsk found at the end of all conditions and with higher Tsk's inthe hot condition than in the cool condition. The, only significantdifference that was revealed by the ANOVA was that final Tsk in the hottrials was significantly higher than final Tsk in the cold trials (p <0.01). There were no significant differences in Tsk due to equipmentensemble or between the two replications. This finding argues against any

physiological acclimatization having occurred between the two replicationsor across the experiment. Comparison of Tsk's between hot and coolconditions over trial duration show significatat differences fromapproximately the beginning through the end of trials. Significantdifferences in Tsk between ensembles appeared toward the end of trials (p <0.05) in both environments.

Thermal Gradients: The thermal gradient en:amined in this study, Tre - Tsk,was studied along the time course of runs. No significant differences wereaiscerned between ensembles in the same environmental conditions,i.e., hotor cool. However, comparing ensembles in different environmentsdemonstrated significant differences resulting across environmentalconditions (p < 0.05), with larger gradients observed in the coolenvironment.

Heat Storage: Environment, i.e., hot versus cool, appears to be responsiblefor the differences observed in this study (p < 0.01). No significantdifferences were observed between garments within an environmentalcondition. Mean S values are given in Table 3.

Sweat Rate: The m w's calculated for the ALSShot trials compared with the

ALSScool and CBRcool trials indicated sign~ificant differences (p < 0.05),as did cumparing CBRhot to ALSScool (p <0.05). Pre-test urine specificgravity showed no statistical differences between configurations,indicating equivalent hydratior levels upon entry into the laboratory.Water consumption was observed to be significantly different betweenALSShot and the two cool conditions (p < 0.05), though not between CBRhotand the cool conditions. No statistically significant difference betweenCBRhot and ALSShot mean water consumption was observed. A statisticalanalysis of evaporative losses could not be made due to missing data. Themean total weight losses, percentage of total body weight lost as sweat,

6

NADC-89009-60percentage of weight lost as evaporation, and total water consumption foreach configuration are given in Table 4.

Cognitive and Psychomotor Data: No effects on either cognitive orpsychomotor testing were discerned as a result of exposure to theexperimental conditions. Neither differences in environmental conditionsnor clothing configurations resulted in any observed changes in Atarisccres or the number of attempts and correct responses to the verticaladdition and Baddeley reasoning tasks (Table 5).

Subjective Responses: Couparing 3quipment, ensembles on the basis ofsubjective criteria zhows that the rate of onset of unpleasant sensationswith ALSShot to be significantly greater than either the ALSS cool orCBRC 0 9 1 (p < 0.04) (Table 6). This was true for all four subjectivecriteria used in this study, i.e., fatigue, wetness, temperature, andcomfort. No significant difference was observed between CBRhot and theother 'ensembles for any of the subjective criteria.

DISCUSSION

The purpose of this study was to determine the impact of wearing theCBR ensemble on thermal homeostasis. It is clear from the analysis ofexposure duration, Tre, and Tsk that the CBR ensemble induces heat stressunder the test conditions. This'stress isparticularly pronounced underconditions of high heat and humidity. Thornton, et al (18') found similarresults, though the stress experienced by their subjects appears to beconsiderably'less than that, observed in this study.

While final temperatures did not vary. significancly betweenconfigurations during hot runs, the differences in onset rates and exposuredurations indicate that the CBR ensemble produced significantly'greaterthermal stress on personnel. The elevated starting Tre observed in the CBRruns was probably a result of'heat storage during dressing with the CBRensemble, heat which was not dissipated ditring the cool down period priorto chamber entry. Tnese results are not surprising consideting the bulk andresulting insulation of the CBR ensemble compared with the ALSSconfiguration. While the MK-I undergarment.is permeable to water vapor, theCBRensemble was found to permit less whole body ventilation, based on mean%E, than the ALSS ensemble and would be expected to result in reducedexposure durations and increased Tre's and Tak's' (10, 14, 18).

The state of hydration must be considered when interpreting thephysiological changes (16). Initial hydration state appears to beequivalent among subjects, based on the initial specific gravities of urinesamples, therefore hydration does not appear be a factor in the observeddifferences. As neither water consumption, Msw, nor the percentege of bodyweight lost through sweating were significantly different between ensemblesin the hot environment, evaporation at the garment surface clearly must beplaying a major role in controlling Tre. It appears that the CBR ensembleis inhibiting the transfer of moisture to the outer garment surface, thusreducing effective heat transfer.

The significant triple order interaction between clothing type,replicatLon, and environmental temperature, is believed to be an artifact

7

NADC-89009-60from experimental procedures. The artifact is thought to have occurredbecause subjects quickly became uncomfortable in the hot conditions, andsubjects in the first replication chose to voluntarily stop trials beforetheir physiological measures indicated a significant heat load. By thesecond replication, subjects were more tolerant of the hot conditions andso their exposure durations were longer and more closely related to thephysiological measures of heat stress. A second factor influencing theinteraction effect is the experimental time limit, since with the ALSSgarment in the cool condition some subjects were removed at 480 minutes,even though both subjective and physiological indices suggested that theycould have endured longer exposures. It is believed that if either of thesetwo factors were eliminated, the interaction effects would be non-significant. Similarly, the significant interaction between the replicationand hot environments for Tre is alst due to this "early out' phenomenon.

The lack of a significant clothing effect on final Tre was ofparticular interest. This non-significant effect indicates that subjectswere reaching s•'ilar final Tre's. However, use of the ALSS ensemble,versus the CBR, led to subjects staying for significantly longer periods oftime before trials were stopped either by the subject or Tre - 39.0°C. Thelack of difference in T can thus be viewed as indicating that the trialswere terminated at smim ar physiological states, though the time to reachsuch a state differed. This may also serve as an explanation for the lackof observed final rsk differences between garments. In addition, thadifferences in rates of change of subjective responses observed betweenclothing configurations may be more a function of exposure duration thanany other factor. It may be that the additional time spent in the ALSShotcompared with the CBRhot is responsible for any perceived differencesbetween these and the ALSScool and CBRcool, respectively.

The relatively small mean exposure duration for the CBR ensemble inhot runs, i.e., 155 minutes, suggests that use of this ensemble may presenta serious impediment to sustained operations due to inability to toleratethe induced stresses. Exposure durations were limited by both high Tre'sand subjective tolerance. Extreme fatigue and discomfort were the causesfor trials to be terminated for subjective reasons. This shows that theonset of high thermal stress, as indicated by final Tre, is brought on at asignificantly faster rate by the CBR ensemble versus the ALSS during heatexposures. Hydration, and thus the blood volume available to muscles (7,16), probably accounted for some of the differences observed in exposuredurations, since blood is preferentialy supplied to muscle tissue duringexercise in heat (15). Reduced hydration, and consequently a reduced bloodvolume, would reduce the muscle blood volume and would ultimately lead tofatigue and exhaustion (7).

It can b,; argued that the hot conditions used in this study arethemselves limiting, as indicated by the mean duration observed for ALSSruns, i.e., 219 minutes. The range of durations for these runs (177-285minutes), however, overlap the observed durations in cool runs for both theALSS (236-480 minutes) and CBR (173-414 minutes). This contrasts with therange observed for CURhot runs (142-175 minutes). This suggests that whilethe ALSS in the heat can be expected to allow perform~nce comparable tocool conditions, the CBR will restrict operatio n to a much shorter time,i.e., less than 3 hours. Though other factors, such as physical

8

NADC-89009-60conditi ning and heat acclimation, would likely increase the durationsobservel for either of the hot runs, it would appear that the CBR ensemblerepreseats a significant impediment to sustained military operations.

Tqis is further supported by the observation that while there isevidencý of habituation with the ALSS under both conditions and the CBRunder c)ol conditions (Figure 2), no such conditioning is witnessed for theCBR ens mble under heat conditions. This suggests that the maximumperformance has been elicited for the CBR ensemble under the hot conditionsof this test.

Tie energy expenditure and cyclic nature of the work load were chosento mode0 helicopter crew missions. Measurements of in-flight work loads(11,19) of helicopter pilots indicate that the energy requirements ofpilotin are low, i.e., approximately 1.5 times or less than at rest. Workloads o' 30W are within this range (20). The cyclic nature of tasks used inthis stady' were an attempt to model the periodic nature of tasks, e.g.,level flight followed by hovering, experienced while flying. Cycling oftasks might suggest that physiological measurements obtained will reflectthe duration of each cycle, thus the physiological responses beingidiosyncratic to a given situation. Mairiaux, et al. (12) have shown thatcycle time is not reflected in changes in Tre but does impact on Tsk andmsw. Si ililar results were found in this study (Figures 5 and 6), thoughit appe rs that the CBR ensemble tended to damp out the response. Thissuggest that the state of hydration will, over time, be affecced andsubsequ ntly lead to an increase in Tre. In addition, modification of Tskwill haie an impact on cognitive and psychomotor performance.

T-e lack of significant changes in the cognitive and psychomotorperformance tasks may be the result of either a lack of test aensitivity(3) or insufficient physiological changes (1) to induce cognitive andpsychomotor deficits. The Atari task has been previously studied and shownto be a sensitive test for performance changes (3), but an earlier heatstress study (8) also resulted in inconclusive changes with regard to Atariperformince. Similarly, the cognitive function tests used have previouslybeen seisitive indicators of cognitive changes (2). Therefore, the resultsfrom th s study suggest that the lack of significant differences are theconsequ nce of inadequate physiological change to elicit a performancechange.

Iý addition to the physiological and psychological indices observedin thisistudy, the functioning of equipment was also monitored. A number ofpotenti lly serious equipment faults were witnessed during this study. Theentire ater supply system presented problems in that subjects complainedit was ifficult to obtain an adequate water flow during drinking. Oneindicat on of the difficulty experienced by subjects attempting to drinkfrom th CBR canteen system was the fact that mean water consumption wasapproxi ately 8 times greater in the hot versus cool ALSS runs, whilenearly qual for the CBR runs. It was found necessary to either use bothhands t squeeze the canteen or to place the canteen on the top of thehelmet f one was to obtain a satisfactory flow of water. Either of thesemethods would probably be untenable in a combat situation since drinkingwould tmus require total concentration, forcing the user to stop performing

9

NADC-89009-60other tasks, if drinking could be accomplished at all in the crampedenvironment of a cockpit.

The breathing filters may also present users with difficulties in ahumid environment. On two separate occasions, new filter cartridges exposedto a 35*C, 70% RH environment for three hours greatly restricted airflow,though the cartridges were not found to be dirty upon visual inspection andthe ventilator operated properly. In both cases, filters were changed topermit the subjects to breath unimpaired. It was determined that thecartridges increased in weight by >35 g, which was believed to be absorbedwater. The air passing through the effected cartridges was described as"warm and moist".

Other problems which were experienced in this study included the fitof the mask and the 9V battery in the communication device. Subjects withcertain facial shapes (2 of 8 volunteers) were found to have difficulty ingetting a good mask fit despite numerous fitting attempts by trainedpersonnel, resulting in considerable leakage occurring around the facialseal. The communication device was found to impose a sufficient electricalload on the battery to require fresh batteries before each trial. This wasafter only very infrequent use of the communication device over an eighthour period. !attery changes while the system is in use appear impracticaldue to the design of the intercom, therefore some means of reducing thepower drain needs to be examined, particularly since more frequentcommunications would decrease battery life.

The results of this study indicate that the CBR ensemble imposes aconsiderable thermal stress on the user, and apparently limits the durationof its use to under three hours on a continuous basis under conditionssimilar to this study. This could present serious problems in a waxtimescenario, when numerous sorties per day would be expected from individuals,requiring the CBR ensemble to be continuously worn, for many hours. Onepossible way of reducing the thermal stress might be imposing lengthy restperiods, much greater than 7 minutes, between activity cycles (12), asituation which was not examined in this study. This would reduce thenumber of perszýnnel available for missions, but might reduce the number ofheat casualties. It is also important to address the equipment weaknessesobserved in'this study, since these design flaws could create potentiallyfatal situations in a chemically contaminated environment for individualsusing the CBR protective zystem.

1) The A/P22P-9(V) ensemble imposes significant heat stress on personnelwearing this ensemble in the hot test ronditions. This suggests thatoperations in hot environments should be limited to relatively shortdurations, i.e., less than 3 hours, when this ensemble is in use.

2) In a cool environment, the A/P 22P-9(V) ensemble imposes no greaterthermal stress than a standard flight suit ensemble.

3) Design changes should be made to correct the problems with the watersupply, breathing filters, and intercom which represent potential hazardsto users of the A/P22P-9(V) ensemble.

10

NADC-89009-60ACKNOULEDGEMENTS

It is the authors' pleasure to acknowledge the invaluablecontributions made by the subjects of this study, whose perseverancedespite personal discomfort made this work possible. We would also like toacknowleage the contributions of the personnel of Code 6025 for medicalsupport, Walter Soroka and Rodney Pursell for keeping the equipmentworking, Nancy Holden, Christopher Zech, and Robert Muller for projectsupport, and Gregory Askew for instrumentation support.

REFERENCES

1. Allan JR and Gibson TM. Seperation of the effects of raised skin andcore temperature on performance of a pursuit rotor task. Aviat. SpaceEnviron. Med. 1979; 50:678-682.

2. Baddeley AD, Cuccaro WJ, Egstrom GH, Weltman G, and Willis MA'. Cognitiveefficiency of divers working in cold water. Human Factors 1975: 17:446-454.

3. Bittner AC, Carter RC, Kennedy RS, Harbeson MM, and Krause M.Performance evaluation tests for environmental research (PETER): Evaluationof 114 measures. Perceptual and Motor Skills 1986; 63:683-708.

4. Brozek J, Grande F, Anderson JT, and Keys A. Densiometric analyses ofbody composition: revision of some quantitative assumptions. Ann. NY Acad.Sci. 1963; 110:113-140.

5. DuBois EF and DuBois D. Measurement of surface area of man. Arch. Int.Med. 1915; 15:868.

6. Fine BJ and Kobrick JL. Effect of heat and chemical protective clothingon cognitive performance. Aviat. Space Environ. Med. 1987; 58:149-154.

7. Harrison MH. Effects of thermal stress and exercise on blood volume inhumans. Physiological Reviews 1985; 65:149-209.

8. Kaufman JW. Heat stress evaluation of anti-exposure' flight gear. NavalAir Development Center. NADC-85061-60, May, 1985.

9. Kolka MA, Levine L, Cadarette BS, Rock PB, Sawka MN, and Pandolf KB.Effects of heat acclimation on atropine-impaired thermoregulation. Aviat.Space Environ. Med. 1984; 55:1107-1110.

10. Light IM, Gibson MG, and Avery AI. Sweat evaporation and thermalcomfort wearing helicopter passenger immersion suits. Ergonomics 1987;30:793-803.

11. Littell DE and Joy RJT. Energy cost of piloting fixed- and rotary-wingaircraft. J. Appl. Physiol. 1969; 26:282-285.

12. Mairiaux PH, Libert JP, Candas V, and Vogt JJ. Physiological andperceptual responses to cyclic heat stress variations. Aviat. SpaceEnviron. Med. 1984; 55:935-940.

11

NADC-89009-6013. Olesen BW. How many sites are necessary to estimate a mean skintemperature? In: Hales JRS (ed.). Thermal Physiology. New York: RavenPress, 1984; p. 33-38.

14. Pimental NA, Cosimini HM, Sawka MN, and Wenger CB. Effectiveness of anair-cooled vest using selected air temperature and humidity combinationsAviat. Space Environ. Med. 1987; 58:119-124.

15. Savard GK, Nielsen B, Laszczynska J, Larsen BE, and Saltin B. Muscleblood flow is not reduced in humans during moderate exercise and heatstress. J. Appl. Physiol. 1988; 64:649-657.

16. Sawka MN,.Francesconi RP, Pimental NA, and Pandolf KB. Hydration andvascular fluid shifts during exercise in the heat. J. Appl. Physiol.:Respirat. Environ. Exercise Physiol. 1984; 56:91-96.

17. Sinning WE, Dolny DG, Little KD, Cunningham LN, Racanielli A, SiconolfiSF, and Sholes JL. Validity of "generalized" equations for body compositionanalysis in male athletes. Med. Sci. Sporcs Exerc. 1985; 17:124-130.

18. Thornton R, Brown GA, and Redman PJ. The effect of the UK aircrewcher•ical defense assembly on thermal strain. Aviat. Space Environ. Med.1985; 56:208-211.

19. Thornton R, Brown GA, and Higenbottam C. The energy expenditure 'ofhelicopter pilots. Aviat. Space Environ. Med. 1984; 55:746-750.

20. Webb p. Work, heat, and oxygen cost. In: Parker JF and West VR (eds.)Bioastronautics Data Book. National Aeron. and Space 'Admin., 1972; NASA SP-3006.

12

/

NADC-89009-60TABLE 1: Physical characteristics of subjects.

Subject Age Height Weight %Body Fat Surface Area(yrs) (m) (kg) (22)

°......... ........ o.o.o........ ...........................

A 23 1.65 65.2 15 1.72

B 24 1.68 63.3 14 1.72

D 35 1.76 92.3 20 2.09

TABLE 2. Equipment configurations worn during tests.

Configuration Protective Garment & ancillaryequipment

Standard Flight a. CWU.27/P flight coverallEnsemble b. cotton long underwear(ALSS) c. flyer's boots

d. flyer's gloves, GS/FRP-2e. CWU-23/P survival vestf. LPU-21C/P flotation deviceg. HGU-60/P helmet

A/P 22P-9(V) a. All items in standard flight ensembleEnsemble b. MCK-3/P CBR protective mask

c. MK-l chemical linerd. CQK-2/P CBR protectise ventilatore. cotton glovesf. 'butyl rubber glovesg. polyethylene socksh. canteen, MIL C 43603i. A/P37S-1 CBR protective intercom

13

NADC-89009-60/TABLE 3. Mean values of erposure duration, rectal temperature (Tre) mean eightad skin tampereuro

ak)' end heat stores. (S), by configuration, resulting fron exposure to ezperimental conditions. The

C onfigurations denoted below are: CDP - A/P 221-9(V) ensemble; ALSS - standard flight suit ensemble.

Values reported are means and standard errors of tLe mean (SDI).

Configuration Exposure Tre Tak Heart S

Duration CC) (C) Rats (w/s2)

(minutes) (beets/mWn)

i f i f i f

CBoRbt mean 155 37.7 38.7 33.5 36.9 84 131 12.2

S;£ 5.3 0.2 0.2 0.1 0.3 4 7 1.5

ALSShot mean 219 37.2 38.6 31.0 36.9 80 139 12.5

Sim 17.9 0.2 0.2 0.3 0.2 2 a 1.2

CBR mean 305 37.2 .37.5 32.3 33.8 91 102 2.8coolI

S IN 41.2 0.2 0.2 0.5 0.2 2 7 1.1

ALSS: el mean 382 37.2 37.4 32,7 33.6 82 19 1.3

SEM 40.3 0.3 0.3 0.3 0.3 5 10 0.4

14

/

NADC-89009-60TABLE 4. Mean values of initial urine specific gravity, water consumption. total sweat rate (Maw).

percentage of sweat evaporated (2E), body weight change, and 2 of total body weight Change, by

configuration, obtained during study. The configurations denoted below are: CBk - A/P 22P-9(V) ensemble;

A.SS - standard flight suit ensemble. Values reported are means and standard errors of the mean (SEM).

Configuration Initial Water M 21 Weight ZBody

Specific Intake ($/min/kg,.ody) Loss Wt. Loss

Gravity (kg) (kg)

CBRhot mean 1.024 0.37 3.50 31.2 1.04 1.3

SD4 0.0008 0.10 0.62 15.3 0.23 0.1

ASS hot mean 1.024 0.79 3.87 41.0 3.57 2.1

SL'l 0.0011 0.27 0.67 12.5 0.29 0.3

CBRool mean 1.026 0.35 1.75 50.7 1.02 1.3

Sul 0.0015 0.29 0.23 11.4 0.23 0.1

ALSSco mean 1.027 0.10 1.26 79.0 0.84 1.1

SEM 0.0011 0.05 0.10 7.9 0.10 0.1

TAiBLE S. Mean values of number of correct responses and attempts for the Baddeley reasoning test and

vertical addition task, by configuration. The configurations denoted below are: CDR - A/P 22P-9(V)

ensemble; ALSS - standard flight suit ensemble. Values reported are means and standard errors of the

"mean (SEM).

Configuration Baddeley Reasoning Vertical Addition

correct attemptl correct attempts

Cmehat mean 18 20 24 15

SEO 1.1 1.0 0.8 0.8

ALSShot mean 19 20 13 14

SOY 0.7 1.2 0.5 0.4

C1 cool -an 21 22 14 15

SLM 1.1 1.1 0.8 0.7

ALSS mean 21 21 14 14cool

SEH 0.7 0.6 0.7 0.6

15

NADC-89009-60TABLE 6. Mean rates at which subjective criteria changed during exposures. Subjectiv• sensations were

evaliated on the basis of 4 ca5egories: fatigue, skin wetness, temperature, end ccmf;:rt. Te rates were

obtained froc,: Rate - (Vf - V P)/t . where Vf . the final reported value for a given Icategory. V - the

value obtained pricr to dressing, and t - the time elapsed when the final value was Obtained. The values

are measured in millimeters fromn the left limit of the scale (see text). The configurations denoted

below are: CBR - A/P 22P-9CV) ersemble; ALSS - standard flight suit ensemble. Values reported are seans

and standard errors of the mean (SEM).

Configuration Rate Im/minute)

Fatigue Skin Temperature Caofort

Wetness

CBRhot mean 0.27 0.39 0.25 0.30

SA 0.10 0.09 0.05 0.10

ALSSho. mean 0.37 0.46 0.36 0.37

SEM 0.09 0.08 0.08 0.10

CBc mean 0.19 0.20 0.13 0.21

SLN 0.07 0.07 0.04 0.06

ALSS mean 0.18 0.23 0.14 0.20

5E11 0 07 0.03 0.05 0.06

16

NADC-89009-60

Itz

Figure 1. The A/P 22P-9(V) Chemical, Biological, Radiological (CBR) protective ensemole as worn inthis study.

17

NADC-89009-60

500

400

w300z

D) 200a I- 0" CBR TRIAL 1

.m. CBR TRIAL 2

0C. FLIGHT TRIAL 1

LU.0 I FLIGHT TRIAL 2

100I I

HOT COOL

Figure 2. Environment suit, and triO efects on voluntary exposure durations.

18

NADC-89009-60

38.5-

38.00

-r 37.5

-6- TRIAL. 1

LU TRIAL 20.- 37.0

36.51HOT COOL

Figur6 3. Environment and trial effects on mean rectal temperature (Tre *C).

19

NADC-89009-60

39-

C. "38.5H-o0* COOL

LU.

37.5LUJ

371INITIAL FINAL

Figure 4. Environmentally induced changes in rectal temperature (Tre °C)

20

NADC-89009-60

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