Effects of severe heat stress on respiration and metabolic rate in resting man.

The effects on metabolic gas exchange, pulmonary ventilation, respiratory rate, heart rate, and end-tidal carbon dioxide tension of increases in deep body temperature of 2 degrees C were studied in adult male human subjects at rest. The increase in pulmonary ventilation (49%) was accompanied by a reduction in end-tidal carbon dioxide tension (17%). Heart rate rose by 85%. The increase in oxygen consumption expressed as a function of body surface area was found to be similar in all experiments (19%), irrespective of the value of the resting oxygen consumption in the control period. There was an associated 18% increase in carbon dioxide production. The results support a hypothesis that the increase in metabolism occurring during heat stress is limited solely to that part of the metabolism defined as basal.