SIMULATION OF HUMAN THERMOREGULATION DURING WATER IMMERSION - APPLICATION TO AN AIRCRAFT CABIN WATER-SPRAY SYSTEM

A model was developed of transient changes in metabolic heat productio n and core temperature for humans subjected to cold conditions. It was modified to predict thermal effects of the upper parts of the body be ing sprayed with water from a system designed to reduce the smoke effe cts of an airplane fire. Temperature changes were computed at 25 body segments in response to water immersion, cold-air exposure, and windy conditions. Inputs to the temperature controller were: (a) temperature change signals from skin segments and (b) an integrated signal of the product of skin and head-core (hypothalamic) temperature changes. The controller stimulated changes in blood flow to skin and muscle and he at production by shivering. Two controller parameters were adjusted to obtain good predictions of temperature and heat-production experiment al data in head-out, water-immersion (0 degrees-28 degrees C) studies in humans. A water layer on the skin whose thickness decreased transie ntly due to evaporation was added to describe the effects of the water -spray system. Because the layer evaporated rapidly in a very cold and windy environment, its additional cooling effect over a 60-min exposu re period was minimal. The largest additional decrease in rectal tempe rature due to the water layer was <1 degrees C, which was in normal co nditions where total decreases were small.