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The effectiveness of microclimate cooling systems in alleviating the thermal burden imposed upon soldiers by the wearing of chemical protective clothing under varying environmental conditions has been examined in a series of studies conducted by the U.S. Army Research Institute of Environmental Medicine on the copper manikin, in the climatic chambers and in the field. Liquid-cooled undergarments (LCU) and and air-cooled vests (ACV) were tested under environmental conditions from 29 C, 85% rh to 52 C, 25% rh. These parameters were chosen to simulate conditions which may be encountered in either armored vehicles, or in desert or tropic climates. We have reviewed seven studies using LCU (including two ice-cooled vests) and six studies using ACV. LCU tests investigated the effect on cooling when the proportion of total skin surface covered by the LCU was varied. ACV tests examined the effects on cooling during different combinations of air temperature, humidity and air flow rates. Additionally, these combinations were tested at low and moderate metabolic rates. The findings from these LCU and ACV studies demonstrate that a) cooling can be increased with a greater body surface coverage by a LCU and b) evaporate cooling with an ACV is enhanced at low metabolic rates with optimal combinations of air flow rates and dry bulb/dew point temperatures, resulting in the ex tension of tolerance time.

The purpose of this study was to determine safe encapsulation time limits in four hot environments including a simulated solar heat load and thereby generate an equation predicting safe time limits for hot environments. Eight male subjects were studied during encapsulation in a Chemical Warfare Agent Protective Patient Wrap in each of four environments. Rectal temperature, mean skin temperature, mean body temperature air temperature and dew point temperature within the wrap and wrap temperature were measured every minute. Metabolic rate was measured during encapsulation by partitional calorimetry. The data shows that safe encapsulation time is severely limited in Hot/Dry and Hot/ Wet environments when a solar heat load is included.

The effectiveness of microclimate cooling systems in alleviating the thermal burden imposed upon soldiers by the wearing of chemical protective clothing under varying environmental conditions has been examined in a series of studies conducted by the U.S. Army Research Institute of Environmental Medicine on the copper manikin, in the climatic chambers and in the field. Liquid-cooled undergarments (LCU) and air-cooled vests (ACV) were tested under environmental conditions from 29 C, 85% rh to 52 C, 25% rh. These parameters were chosen to stimulate conditions which may be encountered in either armored vehicles,or in desert or tropic climates. We have reviewed seven studies using LCU (including two ice-cooled vests) and six studies using ACV. LXU tests investigated the effect on cooling when the proportion of total skin surface covered by the LCU was varied. ACV tests examined the effects on cooling during different combinations of air temperature, humidity and air flow rates. Additionally, these combinations were tested at low and moderate metabolic rates. The findings from these LCU and ACV studies demonstrate that a) cooling can be increased with a greater body surface coverage by a LCU and b) evaporative cooling with an ACV is enhanced at low metabolic rates with optimal combinations of air flow rates and dry bulb/dew point temperatures, resulting in the extension of tolerance time. The application of these findings to industrial work situations is apparent.

Systemic atropine enhances forearm cutaneous blood flow (FBF) but depresses forearm sweating (m sub s) in warm environments, as previously shown in our laboratory. To further examine thermoregulatory consequences of this increased FBF, four healthy males were studied during 30 minutes of seated exercise. Esophageal (T sub es) and mean skin (T sub sk) temperatures, m sub s metabolism (M), heart rate (HR) and FBF were measured during control and following 2 mg (im) atropine. All eight skin temperatures increased with atropine which implies widespread cutaneous vasodilation. The enhanced sensible heat loss with atropine during constant intensity exercise caused T sub es to decrease, resulting in a further significant m sub s depression. The decreased central drive did not result in peripheral vasoconstriction, suggesting that the dilation was peripherally controlled and non-responsive to the thermoregulatory controller. Keywords: Cholinergic blockade.