AD-A280 253

DOT/FAA/AM'94/10 The Effects of Cold

Exposure onWetAircraft Passengers:

Office of Aviation MedicneWashington, D.C. 20591 A Review

Robert P. GarnerBruce C. WilcoxHarvey M. EnglandVan B. Nakagawara

Civil Acromedical Institute

Federal Aviation Adminiscration

Oklahoma City, Oklahoma 73125

DTICMay 19)4 ELECTE f

JUN 1 3 1994D

Final Report

This document is available to the public

through the National Technical InformationService, Springfield, Virginia 22161.

U.S. Department

of Transportation

Federal Avintlnn

94-18213 , - Administration

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This document is disseminated under the sponsorship ofthe U.S. Department of Transportation in the il.erest of

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1. Reort No. 2. Government Arnaesion No. 3. Recipient' Catalog No.

DOT/FKAAIAM-94110I

4. Title and Subtitle 5. Report Date

Effects of Cold Exposure on Wet Aircraft Passengers: A Review May 1994S. Performing Organization Code

7. Author(s) 8. Pt~orming Organization Report No.

Robert P. Garner, Bruce C. Wilcox, Harvey M. England, andVan B. Nakagawara ._ _ .

9. Performlng OrganizatiOn Name and A44fess "Accesion For 10. Work Unit No. (TRAIS)

FAA Civil Aeromedical Institute NTIS CRA&IP.O. Box 25082 DTIC TAB , lOklahoma City, OK 73125 Unannounced o 11. Contract or Grant No.

Justification

12. Sponaoring Agency name and Addresa By .3. Type of Report and Period Covered

Office of AMiation Medicine Distribution IFederal Aviation Administration Availability Codes800 Independence Avenue, S.W. Aalblt oe

Washington, DC 20591 Avail and I orDist Special 14. SDoonorlng Agency CodeL415, Suippiemental Notes

16. Abstract

The incorporation of a cabin water spray system (CWSS) aboard commercial passenger aircraft has beensuggested as a mechanism of reducing passenger death and injury from the fire and smoke commonlyassociated with aircraft accidents. A potential health risk associated with a CWSS is the physiologicalstress that would be imposed upon an individual by being wet from a CWSS in the aircraft cabin and thenevacuated into a cold environment. The severity of this type of exposure would be proportional to thedegree to which the individual was doused with water and the wind speed and inversely proportionally tothe ambient temperature. The physiological responses to partial wetting and subscqumnt exposure to coldenvironmental conditions have not been studied. The effects of cold exposure as well as the degree ofprotection provided to the individual, particularly the cardiorespiratory system, by CWSS would need tobe fully investigated to determine if the survilv. benefits of a CWSS outweigh the potential health risks.

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Aviation Thermoregulation Hypothermia Document is available to the public through theNational Technical Information Service,Springfield, Virginia 22161.

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EFFECTS OF COLD EXPOSURE ON WETAIRCRAFT PASSENGERS: A REVIEW

INTRODUCTION central and peripheral sensors and evokes responses tomaintain thermal balance.

Body heat balance is one of the most well regulated The preoptic area of the hypothalamus has recep-control systems of human physiology. In a dry envi- tors that are sensitive to both heat and cold (2). Thisronment at temperatures between 60 and 130"F, area of the brain is often referred to as "the body'sregulatory mechanisms are capable of maintaining thermostat." Activation of these receptors evokes in-normal body temperature of 98.6 s 1.4"F (1). To tense thermoregulatory responses. Similarly, the pe-complement this control system, humans have deved- ripheral receptors sense the presence of either heat oroped behavior patterns allowing them to live in envi- cold. These include receptors in the skin and someronmenes of extreme heat and cold. The purpose of internal organs. The majority of peripheral tempera-this review is to consider the physiological responses ture receptors are sensitive to cold. The hypothalamusof humans removed from a controlled environment, integrates the input from both preoptic and periph-the interior of a passenger aircraft, and exposed to the eral receptors and transmits signals to the periphery toelements after saturation with moisture from a cabin evoke the appropriate response to maintain heat bal-water spray system (CWSS), proposed for fighting ance.onboard fires while improving passenger evacuationtime. Mechanisms Involved in Body Temperature

To predict thc responses of an individual, an un- Homeostasisderstanding of the physiological response to thermal The human body is constantly undergoing heatstress is required. These responses must be evaluated flux. The control system for body heat balance func-with respect to pertinent physiological and environ- tions so that body heat is lost or dissipated in warmmental conditions. Specifically, the focus is on an environments and conserved in cold environments toemergency situation aboard an aircraft in which a keep internal core temperature relatively constant (3,CWSS is activated. 4). Temperature homeostasis occurs when heat loss

equals heat gain. This relationship can be considered

Control System for Body Temperature in the following terms (5).Homeostasis AH = M ± Cd ± Cv ± R - E (Equation 1)

As is true for most physiological control sys- whereteins, temperature regulation depends upon nega- AH = Change ir body heat contenttive feedback mechanisms. A negative feedback M - Metabolismcontrol system is defined by the output of the Cd - Conductionsystem suppressing or inhibiting the activity of the Cv = Convectionsystem. For control of body temperature, this re- R - Radiationquires receptors at the periphery to send signals E - Evaporationback to the brain, which must integrate the infor- Each of the variables on the right side of the abovemation and evoke the appropriate response. For equation requires a gradient, over which energy can bebody temperature control, this system is compli- exchanged. Each mechanism of heat transfer is brieflycated by the temperature at the body surface being described below and discussed with respect to itslower than the internal core temperature. To rec- contribution to heat exchange in body temperatureoncile this discrepancy, a particular area of the regulation.brain, the hypothalAmus, integrates input from both

Metabolism. The body is constantly producing serve body heat. In general, the body attempts toheat as a by-product of cellular metabolism. In a warm increase heat production, while trying to minimizeenvironment, excess metabolic heat is lost through a heat loss. To minimize hear loss, cutaneous vasocon-combination of radiation, conduction, convection, striction reduces the amount of blood flow to the skin,and evaporation. In a cool environment, metabolic thereby reducing the amount of heat that can be lostheat can actually be increased by shivering, to help at the body's surface through radiation, convection,maintain body temperature at an appropriate level, and conduction (7). Piloerection of body surface hair

Radiation. Radiation refers to the loss or gain of occurs to trap a layer of warm air next to the skin andheat by infrared heat waves. Normally, people exist in provide insulation. This mechanism is an ineffectivean environment in which the temperature is below means of conserving body heat in humans.their body temperature and therefore lose heat to the For maintaining normal body core temperature,environment via radiation. regulatory mechanisms for increased heat production

Conduction. Refers to the transfer of body heat are more numerous and more effective than mecha-directly toor from anothericbject. Usually, theamount nisms operating to minimize heat loss. Increases inof heat lost or gained by the body in this manner is bcdy heat production are elicited byboth indirect andminimal. direct means. Increased secretions of both epineph-

Convection. Refers to the special case of heat con- rine and norepinephrine results in an increased basalduction to air molecules at the body's surface. The air metabolism, thus increasing metabolic heat produc-molecules are carried away from the body by air tion (8, 9). The release of these catecholamines iscurrents. characteristic of a generalized stress response. Fur-

Evaporation. Evaporation of one milliliter (ml) of thermore, there is increased secretion of thyroid stimu-water results in a heat loss of 0.58 kilocalorie (kcal)'. lating hormone (TSH) from the anterior pituitary.Humans lose a minimum of 600 ml of water a day Increases in TSH result in increased activity of thefrom the skin and lungs by evaporation, regardless of thyroid gland and the accompanying release of thy-environmental conditions. As can be seen from Equa- roxine, which increases basal metabolic rate. Althoughtion I, evaporative mechanisms of thermal regulation not a completely conscious act, individuals have thearc only effective as a means of heat dissipation. In a tendency to increase motor activity when exposed tovery hot environment, evaporative heat loss can be the cold in order to enhance heat production. In responseonly way in which the body can eliminate excess heat. to a drop in body temperature, shivering occurs.However, evaporative heat loss decreases as relative Shivering is a result of increased skeletal muscle tonehumidity2 increases. It is for this reason that a hot, and can multiply body heat production four to fivehumid environment is so dangerous when performing times (10). Another mechanism of body heat conser-physical activity. vation is the transfer of heat to deep veins in the limbs,

which are parallel and in close proximity to arteries.Mechanisms Activated by M.derate Body This is referred to as counter-current heat exchangeCooling (11, 12). The extent to which the above responses

When an individual is exposed to a cool or cold would occur is dependent upon the intensity of theenvironment, specific physiological responses are cold stimulus present. Figure 1 presents a simplifiedevoked. Initially, cold induced stimulation of the schematic of the negative feedback system controllingcutaneous thermal receptors sends signals to central body temperature in a cold environment.thermoregulatory areas, triggering responses to con-

'A kilocalorie is defined as the amount of heat required to raise 1 kilogram of water I "C.'Relative humidity is defined as the ratio of the mol fraction of water vapor present in a volume of air to the tool fraction present

in saturated air, both at the same temperature and pressure (6).

2

Set Points

" ~Central

S~Integrator

Exercise Metabolism Vasoconstriction

Limbs Muscles RespirationSkinSHeeat

Heat ProductionConservation Ls

BodyTemperature

Convective/Evaporative

S' '!- Cold

!Environment

Figure 1. Simplified schematic of the negative feedback system which attempts to regulate bodytemperature dUring exposure to a cold environment. For an individual sprayed with water, it is importantto note that the degree of convective and evaporative heat ioss occurring will depend upon the watersaturation level and enviionmental factors, such as temperature and wind speed.

-3

Impact of CWSS on Aircraft Pasengtrs as burns, broken bones, blood loss, etc., can markedlyIn assessing the affect ofa CWSS on aircraft passen- influence an individual's physiological response to a

gers it should be realized that no two individuals, given stimulus.crashes, or crash environments are identical. There- The Emergency Situation. Cabin water spray sys-fore, certain assumptions must be made to evaluate tems are relevant to passenger survival in postcrashand predict the thermoregulatory challenge individu- fire situations. Even in accidents in which individualsals would face after exposure to a CWSS. The impact survive impact forces, fire and smoke are a major causeof a CWSS must be considered with respect to indi- of passenger death. People are killed by burning fuelvidual differences in passengers, the emergency situa- and aircraft structure, in addition to the associatedtion triggering the activation of the CWSS, and the smoke and toxic fumes. Conceptually, a postcrashenvironment that passengers will be exposed to after cabin water spray system would retard the spread ofevacuation from the aircraft. Each of these variables is fire in the aircraft cabin, thus allowing greater oppor-discussed below. tunity for passenger evacuation (14, 15). The passen-

The Passenger. For the purposes of this review, the gers may become wet from the water spray systemairline passengers are considered to be healthy adult during this time period. The effect of this wetting onindividuals who have no significant physiological body temperature regulation would depend upon aimpairments and will respond to cold exposure con- number of factors, including: 1) the degree of wetting,sistently with the physiological responses previously 2) clothing, 3) the ambient temperature and winddescribed. However, it should be recognized that speed of the environment into which the individualsaboard any given passenger flight there will be a were evacuated, and 4) the length of time they re-heterogeneous population of individuals whose indi- mained in the hostile environment before being placedvidual characteristics will influence the physiological in safe, thermo-regulated surroundings.responses to cold exposure. Factors influencing an The Evacuation Environment. Seasonal varia-individual's response to a cold environment include: tions of the ambient temperature influence the rate ofage, sex, ethnic background, body frame size and body body heat loss. In spring, summer, and early autumn,composition, physical conditioning, and basal meta- or in areas where temperatures remain warm, bodybolic rate. The person's food, fluid, and alcohol con- heat loss resulting from exposure to a CWSS wouldsumption will also help determine the response to not appear to pose a significant problem. For thecold. In addition to these influences, persons suffering purposes of this discussion, it is assumed that thefrom any type of disease or physical handicap need passengers will be evacuated from the aircraft cabintheir response to a cold environment to be considered into a cool or cold environment. Only a few accidentswith respect to the particular pathology or impair- with postcrash fire have occurred in sub-freezingment from which they suffer. conditions. An outline of the factorf influencing the

Assuming that a significant majority of individuals magnitude of the physiological response to cold wateron a passenger aircraft that crashes would consider the immersion, cold diy conditions, and the hypotheticalexperience highly stressful, the physiological responses situation of being sprayed and introduced into a coldassociated wi~h the generalized stress response of this tnvironment is presented, in Table 1.situation include many of the responses that are elic- The colder the ambient temperature, the greaterited by exposure to cold (13). Catecholamine levels the body heat loss. Potentially, even relatively briefand metabolic rates would increase, and motor activ- exposure to extremely cold environment may result inity levels, associated with bracing for impact and cold injury, frostbite or hypothermia (Appendix I).evacuation, would also be ele-.,ated. This is important The reason is that in extremely cold air the rate of heatbecause much of the "reserve" of the thermoregula- loss by convection becomes vcry large since the coldtory control system is already activated. Furthermore, air is capable of removing all the heat that canthe impact of crash induced injury on thermoregula- diffuse through tl'e subcutaneous insulation of thetory mechanisms should be considered. Injuries such skin. Furthermore, the physiological stress of the

4

Influences Dry Water Immersion Spray

BehavioralExercise -------------------------------. X ........-------------- X ----------------------- X

EnvironmentalAir Temperature -------------------- X -------------------------------------------------- XHumidity ----------------------------- X -------------------------------------------------- XWater Temperature -------------------------------------------. X ---------------------- XWind Velocity ---------------------- X -------------------------------------------------- X

IndividualBasal Metabolism -------------- X - --------------- X - --------------XBody Composition ----------------- X ----------------------- X ----------------------- XBody Somatotype - ----------- X - --------------X- -------------- XPathological Conditions ---------- X ----------------------- X ----------------------- XPhysical Condition (Fitness) ----- X ----------------------- X ----------------------- X

SituationalClothing ------------------------------ X -------------------------------------------------- XExposure Time ---------------------- X ----------------------- X ------------------------ X

Table 1. A listing of some of the factors that will influence an individual's response to cold exposure.Behavioral and situational influences can be manipulated so that probability of injuries, such as frostbite,can be reduced when exposed to a cold environment.

cold environment will be increased by exposure mois- associated with an emergency landing, occurs in ature from a CWSS. If an individual's clothing be- more remote area, the chances of clinical problems

comes wet, it is no longer an effective means of arising from exposure would be greatly increased.preventing heat loss from the body, due to the high Clinical manifestations of exposure such as above-

heat conductivity of the water. In fact, wet clothing freezing cold injury, frostbite, and hypothermia couldmay actually enhance the rate at which heat is lost be expected to be positively correlated with the amountfrom the body. Body heat los: would be further of time required to deliver rescue personne! to theaugmented by any air flow present in the evacuation crash site, the ambient temperature, and the windenvironment. The influence of wind speed on heat speed at the evacuation site.loss from the body has been well characterized and isdefined as windchill (Appendix 1I). For these reasons, Application of Available Datapassenger evacuation from the aircraft cabin into a The physiological responses and dangers ofpassen-

cold environment after exposure to a CWSS poses a gets doused by a CWSS during evacuation from anpotential threat to the individual's well-being. The aircraft cabin can be approximated for a given set ofextent to which this is a problem depends a great deal environmental variables by applying what is presentlyupon the availability of appropriate rescue services known about cold exposure to this specific situation.and medical facilities. For example, a sprayed person who evacuates into

If the air-raft CWSS activation occurs during take- a 32'F environment with a wiid of 15 miles per hour

off or landing at an airport that had rescue facilities will face a severe thermoregulatory challenge. In thisimmediately available, the health risk resulting from situation, the effective ambient temperature is 13"F.exposui.- can be considered minimal. Exposed indi- A 15'F ambient temperature with a 15 mph windvidtiak could be taken directly to health care facilities, rec,,h- in an effective ambient temperature of-14"F.be treated, and monitored. If activation, like that Frostbite occurs at a tissue temperature of about -2"F.

5

If protective measures are not taken, the chance for The degree of protection a CWSS actually offers thefrostbite injury is very real, particularly to the body respiratory system should be determined. Specifically,extremities or expused skin. If emergency medical the impact of a CWSS should be evaluated in terms ofattention is not forthcoming, core body temperatures the degree of protection it provides lung anatomy andcould decline to hypothermic levels. biochemicals necessary for breathing. Consideration

lfan evacuation were to occur into an environment should also be given to what other physiologicalbelow -5'F at a wind speed of 15 mph. mechanisms challenges are presented by the CWSS itself, e.g.,for survival in the cold, would have to be 2vailable. inhalation of dissolved toxins, superheated water va-This combination of temperature and wind speed por, etc. This research would allow assessment of bothresults in an effective ambient temperature of-37"F; the short term and long term benefits offered by aexposed flesh freezes in less than one minute. There- CWSS to an individual's respiratory function.fore, unless rescue personnel are at the crash siteimmediately, severe cases of frostbite and hypother- REFERENCESmia would occur.

In each of these situations, the effective ambient 1. Guyton A.C. Body Temperature, Temperaturetemperature would be further lowered by any evapo- Regulation and Fever. In Guyton A.C. Textbook of

ration of CWSS water from the skin and clothes. It is Medical Physiology, 7th. Ed. W.B. Saunders Co.,

difficult to estimate how severe an effect this, and Philadelphia, 1986, pp. 849-860.

other levels of exposure, would have on the average 2. Hori T., Kiyohara T. & Nakashima, T.Thermosensitive neurons in the brain - the role in

person. homeostatic functions. In Mercer, J.B. (ed.) Ther-mal Physiology, Elsevier Science Publishers, New

CONCLUSIONS AND RECOMMENDATIONS York, 1989, pp. 3-12.3. Rowell, L.B. Human adjustments and adaptations

The focus of this paper has been the effect of cold toheat stes Here adduhowsIn aotis nsto heat stress - where and how? In Folinsbee L.J.,

exposure on individuals that have been doused by a WagnerJ.A., BorgiaJ.F., Drinkwater B.L., GlinerCWSS. Rese:rch studies have not :dt-quately ad- J.A., and Bedi J.F. (eds.) Environmental Stress:dressed the effect of conductive and evaporative heat Individual Human Adaptations, Academic Pressloss due to a person being doused with water and then Inc., New York, 1978, pp. 3-27.introduced into a cool or cold environment. The 4. Buskirk E.R. Cold stress: a selective review. Inpossibility of cold injury occurring during this type of Folinsbee L.J., Wagner J.A., Borgia J.F.,exposure is substantial. Since it would be inappropri- Drinkwater B.L., Gliner ].A., & Bedi J.F. (eds.)ate to expose individuals to conditions that could Environmental Stress: Individual Human Adapta-

tions, Academit. Press Inc., New York, 1978, pp.actually induce cold injury, experiments need to be 249-266.designed to develop models to help predict the sever-ity] of cold injury expected under variable environ- 5. Adams T. & Iampietro P.F. Temperature Regula-

of pfoldras enge rcoting tion. In Falls H.B. (ed.) Exercise Physiology, Aca-mental conditions and levels of passenger clothing demic Press, New York, 1968, pp. 173-196.water saturation. These efforts are importart becausethe potential for enhanced accident survivability pro- 6. Bligh J. & Johnson K.G. Glossary of terms for

thermal physiology. I Appl. Physiol. 35:941-961,vided by a CWSS probably outweighs the risk of 1973.serious harm from environmental exposure. Currently, 7. Grayson, J. Responses of the microcirculation thowever, it is not possible to quantify this risk conm- ho raysnd cl Renronments. o n thm onm E

arison.hot and cold environments. In Schonbaum, E. &parison. Lomax, F. (eds.) Thermoregulation: Physiology and

There are a number of other questions pertinent to Biochemistry, Pergamon Press, Inc., New York,physiological issue: that should be assessed in evaluat- 1990, pp. 221-234.ing the advantages and disadvantages of a CWSS in 8. Ga!e C.C. Neuroendocrineaspectsoftherm- gu-protecting aircraft passengers from fire and smoke. lation. AnnualRex. Physiol. 35:391-430, 1973.

6

9. Therminarias A., Flore P., Oddou-Chirpaz M.F., 13. Guyton A.C. The autonomic nevous system; theGharib C., & Gauquelin, G. Hormonal responses adrenal medulla. In Guyton A.C. Textbook ofMedi-to exercise during moderate cold exposure in young cal Physiology, 7th. Ed. W.B. Saunders C . Phila-vs. middle-aged adults. I Appl. Physiol. 73:1564- delphia, 1986, pp. 686-696.1571, 1992. 14. Barthelmess, S. The Manchester accident - the

10. Kleinebeckel, D. & Klussmann, F.W. Shivering. final chapter. Flight Saftty Digest 8:1-10, 1989.In Schonbaum E. & Lomax P. (eds.) Thermoregu- 15. Hill, R., Marker, T., & Sarkos. Evaluation andLation: Physioloy andBiochemistry, Pergamon Press, optimization of an on-board water spray fire sup-Inc., New York, 1990, pp. 235-253. pression system in aircraft. Water Mist Fire Sup-

11. Tikuisis P., Gonzalez R.R., & Pandolf K.B. Pre- pression Workshop. March 1-2, 1993. Proceed-diction of human thermoregulatory responses and ings pp. 93-103. NISTIR 5207.endurance time in water at 20 and 24"C. Aviat.Space Environ. Med 59:742-748, 1988.

12. Raman E. & Roberts M. Heat savings from alter-ations of venous distribution versus counter-cur-rent heat exchange in extremities. In Mercer, J.B.(ed.) ThermalPhysiology, Elsevier Science Publish-ers, New York, 1989, pp. 167-172.

7

APPENDIX A

CLINICAL MANIFESTATIONS OF COLD blood flow, and the red blood cells cannot remainEXPOsURE suspended in the small, slowly moving volume of the

cooling serum. As the red blood cells settle in theFrostbite vessels, clotting occurs, farther obstructing the flow

Frostbite occurs when the skin temperature ap- of blood. Eventually, these processes totally halt cir-proaches the freezing point of water. The areas most culation to the exposed tissue.readily affected by frostbite are the apical areas of thebody: hands, fingers, toes, ears, nose, and chin. Mild Hypothermiacases produce numbness, prickling and itching. As the Hypothermia is defined as a body core temperaturecondition worsens, paresthesia and stiffness occur. at or below 95"F. Figure 2 graphically depicts theThe first clinical sign of frostbite is pale tissue color physiological responses associated with exposure to aIf untreated, tissue coloration progresses to a red- severely cold environment. The time required for eachviolet hue and eventually turns black, as the tissue response to manifest itself will vary with the environ-dies. After recovery from severe frostbite, the skin and mental variables, such as temperature, windchill, wa-nails of an affected extremity may grow back, but ter immersion, etc.permanent loss of motion may result. In the most Shivering starts when the core temperature starts tosevere cases, amputation of the affected area may be drop from the normal temperature of 98.6"F. Whenrequired. Although frostbite is usually regarded as an the body temperature drops to approximately 95"F,external problem, in cases of extreme exposure it can an individual begins to feel confused and disorien-occur in the lungs and nasal passageways. tated. If core temperature continues to fall, amnesia

The factors that affect the development of frostbite may occur. At a core temperature of approximatelyare temperature, windchill, humidity, duration of 91.5'F, shivering ceases and the skeletal muscles mayexposure, and, to some extent, altitude. Frostbite can become rigid. Cardiac arrhythmias may also becomeoccur without an associated drop in core temperature manifest at this point. It is important to note thatof the organism. The diuration and type of cold expo- when shivering stops, the body has lost the battle tosure are the most important factors to be conwidered. maintain its internal temperature and the person willComing into direct contact with certain materials can need medical assistance to recover.cause almost instantaneous frostbite injury. Touching At a core temperature below 91.5"F, the personcold wood or fabrics is not as dangerous as direct becomes semi-conscious and loses awareness of thecontact with cold metal, especially if the skin is wet or surroundings. The pupils of the eyes usually dilate.damp. This fact may be particularly relevant during Unconsciousness occurs at a body core temperature ofevacuation from an aircraft and subsequent environ- 86"F. Tendon reflexes are greatly diminished and wil!mental exposure after being doused by a CWSS. completely disappear if the core temperature contin-

Mechanistically, frostbite damage is caused by the ues to drop. Further reduction in core temperature tofreezing of cellular cytoplasm. As the cell water crys- 82.5'F induces ventricular Fibrillation and death soontallizes, cellular enzymes and membranes are damaged follows. As illustrated in Figure 2, an unabated dropor destroyed. More importantly, this freezing ob- in core temperature r( sults in death from cardiovaqcu-structs the blood supply to the tissue. The endothelial lar failure. However, renorts exist of individuals beingcells lining the capillaries and small veins in frostbit- resuscitated after their body core temperature fell toten tissues are damaged by the cold in such a manner 68"F. Ther-fore, even a person with no visibl. signs ofthat they allow the blood serum to leak into the life should not be pronounced dead until vital signssurrounding tissues. Loss of this fluid diminishes ate not evident at an increased body temperature.

A]

Sensation of ColdShivering 98.6

Mental ConfusionLoss of Physical Orientation 95

.C Possibility of Amnesia

Cessation of ShiveringMuscle Rigidity I

a_ Cardiac Arrhythmias

Dilated PupilsSemi-Consciousness under 91.5

Unconsciousnessco Loss of Tendon Reflexes 86

Ventricular FibrillationDeath 82.5

Increasing Exposure Time )"

Figure 2. Progression of physiological responses when exposed to cold conditions for an extended periodof time. The time required for each set of responses to occur will depend upon the severity of theenvironmental conditions.

Both immersion and dry conditions have been monitored. There has been a lack of research examin-

used to study hypothermia. In immersion studies, the ing the effects of a cold, windy environment on a wetprimary focus has been the interaction of temperature individual. Unfortunately, this scenario is most perti-and exposure time. To evaluate hypothermia in dr1' nent to possibledeleteriouseffectsofaCWSSon bodyconditions, wind speed, air temperature, and humid- temperature regulation.ity are varied and the impact on core temperature

A2

APPENDIX B

WINDCH ILL

"Windchill is a term used for the additional effect on body temperature as a cold environmen-cooling effect produced by the wind. Air around a tal temperature with no air movement. For ex-person is warmed by coming into contact with the ample, a temperature of 23'F with a 25 mph wind

skin through the process of convection. When the is equivalent to a temperature of -10F in the

newly-warmed air is moved away, cool air moves in amount of heat that will be lost from the body.to take its place and begins the process of removing Figure 3 is a graph showing how wind speed and

heat from the skin. For this reason, a mild tem- actual air temperature combine to produce an

perature with a high wind speed can have the same equivalent temperature.

Windchill ChartEquivalent Temperature in terms of 0 mph

50

5 mph

S 25-- 15 mph

--- -25 mph

t-,, -25 - -...2 -. .. 35 mph

-50-

-5 --. 45 mph

-75 .7

35 30 25 20 15 10 5 0 -5

Ambient Temperature (OF)

Figure 3. Impact of wind speed on equivalent temperature at ambient temperatures from 0 to35"7. The most drastic reduction in equivalent temperature is elicited by a breeze of only 15mph. Reduction of equivalent temperature at higher wind speeds is not as profound.

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