Physiological and psychological effects of heat stress simulating cockpit conditions.

It is generally accepted that physiologically tolerable heat stress can adversely affect human performance, but it is difficult to predict the impact of a specific environment. Experiments were designed to determine the effects of thermal conditions similar to those occurring in aircraft cockpits in warm climates, where both high air temperatures and radiant heat play important roles. Subjects (n = 13) were exposed to heat for 2 h, had a 30-min break, then repeated the exposure. Conditions were Tdb = 35 degrees C and Twhb = 26 degrees C, with or without use of infrared lamps which raised globe temperature to 47 degrees C. Measurements included skin, rectal, and esophageal temperatures, heart rate, weight loss, and hematocrit. Subjective Fatigue Estimates (SFE) and Repetitive Psychometric Measures (RPM) were performed before, during, and after each heat stress. Both thermal conditions were physiologically compensable but induced marked subjective fatigue and altered the learning curve for some subtests of the RPM. Similar conditions in aircraft can be associated with impaired performance, particularly in new or emergency situations.