Effects of hypoxia and hyperoxia on ventilatory kinetics during recovery from exercise.

The purpose of this investigation was to determine the effects of breathing hyperoxic and hypoxic gas mixtures on ventilatory kinetics in the transition from submaximal exercise to rest. Eight male subjects performed three separate single blind exercise tests at 80% of their ventilatory threshold. Inspired oxygen concentration was varied in each experimental condition: test one (55% O2 -45% N2), test two (14% O2 -76% N2), and test three (21% O2 -79% N2). Ventilation, heart rate, and gas exchange were measured every 15 s for 6 min of exercise and during 9 min of recovery from exercise. Data analysis revealed no significant (p less than 0.05) differences in the kinetics of heart rate, oxygen uptake, expired volume of carbon dioxide, or ventilation among treatments during the transition from exercise to rest. Given the belief that hyperoxia attentuates the carotid bodies and hypoxia augments carotid body chemosensitivity, these findings suggest that the carotid bodies are not important regulators of VE kinetics during recovery from exercise.