VENTILATORY RESPONSE TO HYPOXIA IN ELDERLY HUMANS

In young adults the ventilatory response to 25 min of isocapnic hypoxia (SaO2 = 80%) is characterized by an initial increase in ventilation followed by a decline. The increase and decline are proportional. Because older adults have been reported to have reduced initial ventilatory responses to hypoxia, we compared responses to hypoxia in 14 older (mean age 62) and 15 younger (mean age 29) subjects. There was no difference. Both groups demonstrated a similar initial increase in ventilation with hypoxia and a similar subsequent decline due to a decline in tidal volume. In both groups the size of the initial increase was proportional to the subsequent decline. In both groups hyperoxia immediately after 25 min of hypoxia transiently depressed ventilation, while hyperoxia after room air breathing did not. We conclude that the ventilatory response to 25 min of hypoxia is independent of age in normal humans.