Thermoregulatory, cardiovascular, and psychophysical response to alcohol in men in 40°C water

The goals of the study were to test the hypotheses that ethyl alcohol (ETOH) in low-to-moderate doses would alter thermoregulation and/or disrupt the normal relationship between physiological and psychophysical indexes of heat stress during 40°C water immersion and to characterize the cardiovascular response to the combined stimuli of heat, water immersion, and ETOH. Six healthy men underwent three trials of 21 min of immersion in water at 40.0 ± 0.1°C after consuming 0, 0.27, or 0.54 g ETOH/kg. Esophageal temperature (T(es)) rose by ~1.0°C during immersion for each trial. Per unit of T(es) rise, changes during immersion in skin temperature, sweat rate, heart rate, systolic and diastolic blood pressure, and psychophysical assessments of comfort and overheating did not differ significantly by trial. Across trials, there was an apparent threshold for activation of thermoregulatory responses at an ~0.5°C increase in T(es) occurring after ~9 min of immersion. This threshold was identified psychophysically by increased ratings of overheating and decreased comfort. Above the threshold, there was an attenuation of the rate of increase of T(es). Cardiovascular stress was mild (rate-pressure product ~12,000) and not significantly increased by ETOH. Hypotension and tachycardia when subjects stood to exit the tub were observed. The data suggest that ETOH at the doses administered does not affect thermoregulatory, cardiovascular, or psychophysical indexes of heat stress during 40°C water immersion.