Changes in respiratory control in humans induced by 8 h of hyperoxia

bins. Changes in respiratory control in humans induced by 8 h of hyperoxia. J Appl Physiol 89: 655–662, 2000.—In humans, 8 h of isocapnic hypoxia causes a progressive rise in ventilation associated with increases in the acute ventilatory responses to hypoxia (AHVR) and hypercapnia (AHCVR). To determine whether 8 h of hyperoxia causes the converse of these effects, three 8-h protocols were compared in 14 sub-jects: 1) poikilocapnic hyperoxia, with end-tidal PO2 (PETO2) 5 300 Torr and end-tidal PCO2 (PETCO2) uncontrolled; 2) isocap-nic hyperoxia, with PETO2 5 300 Torr and PETCO2 maintained at the subject’s normal air-breathing level; and 3) control. Ventilation was measured hourly. AHVR and AHCVR were determined before and 0.5 h after each exposure. During isocapnic hyperoxia, after an initial increase, ventilation progressively declined (P, 0.01, ANOVA). After exposure t