Effects of acute hypoxia on ventilatory response at the onset of submaximal exercise

In order to investigate the effects of acute hypoxia and accompanying hypocapnia on the ventilatory response at the onset of dynamic exercise, four healthy adult men performed 50W rectangular loads on a cycle-ergometer in normoxic (FIO2 = 0.21) and hypoxic (FIO2 = 0.11) conditions. No statistically significant differences in the initial ventilatory responses to exercise (both delta VI and delta VE assessed on a breath-by-breath basis) were found between eucapnic normoxia (PETO2 approximately 95, PETCO2 approximately 42 Torr) and hypocapnic hypoxia (PETO2 approximately 45, PETCO2 approximately 35 Torr). The present findings support the contention that the neurogenic ventilatory drive at the onset of early exercise is independent from PO2 and PCO2.