Study of the effect of prior sustained hypoxia on the ventilatory response to exercise in humans

An 8‐h period of hypoxia results in a lowering of end‐tidal PCO2 that persists following the return to breathing room air. This study sought to determine whether the ventilatory response to air‐breathing exercise was altered by such an exposure. Eight subjects were studied on two days. On one day, the subjects were exposed to 8 h of isocapnic hypoxia (end‐tidal PO2 55 Torr) and on the other day, the subjects were exposed to 8 h of euoxia as a control. Before and after each exposure, the subjects undertook an incremental exercise test to exhaustion. Repeated measures ANOVA on end‐tidal PCO2 indicated that the reduction in end‐tidal PCO2 (~3 Torr) following hypoxia remained constant during exercise. We conclude that the small increment in the ratio of ventilation to metabolism induced by 8 h of hypoxia persists at the higher metabolic rates occasioned by muscular exercise.