Preflight Heat Stress and Recovery
AIR FORCE AEROSPACE MEDICAL RESEARCH LAB WRIGHT-PATTERSON AFB OH
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Changes in physiological responses during heat stress as experienced in summer preflight operations have been studied with four sitting, resting subjects wearing Air Force standard fighter clothing assemblies. After exposure to chamber temperatures of 45, 50, and 55 deg C 25 mmHg water vapor pressure and 1.1 msec air velocity for either 30 or 60 minute periods, the temperatures were lowered rapidly 5 minutes to 15, 20, and 25 deg C, respectively, for a 30-minute poststress recovery period. Skin temperature, rectal temperatures, heart rates, body heat storages, sweat and evaporation rates were determined and graphically presented. The time required to return to prestress baseline physiological values for all thermal stress conditions is given in tabular form. As expected, recovery time was a function of the ambient recovery temperature level that followed the heat exposure. The recovery temperature should not be lower than 20 deg C if discomfort is to be avoided. Heart rate decrease appears to be a reliable indicator for recovery. The rectal temperature remained at an elevated level after all other measured physiological responses returned to baseline level. In an additional series, applying identical heat stresses, the subjects head was ventilated with 2.5 CFM dry air at 10 deg C. In comparison to the experiments without head ventilation, reduced skin temperatures and increased evaporation rates were observed.
- Stress Physiology