VENTILATORY RESPONSES TO SUSTAINED EUCAPNIC HYPOXIA IN HEALTHY-MALES DURING WAKEFULNESS AND NREM SLEEP

The effects of sustained eucapnic hypoxia (SEH, 20 minutes SaO(2), sim ilar to 80%) on ventilation and supraglottic airflow resistance (Rua) plus genioglossal (gg) and diaphragmatic (di) electromyograms (EMGs) w ere compared during wakefulness and nonrapid eye movement (NREM) sleep in six healthy normal male subjects. ;Early augmentation of Ventilati on was followed; by decline or roll-off in both states. The augmentati on of ventilation was less in sleep than wakefulness (e.g., after 5 mi nutes hypoxia, 140% and 167% of baseline, respectively, p < 0.05). Thi s appeared to be due to three factors: I) sleep-related increases in R ua [the ventilatory responses to SEH (sleep vs. awake) were inversely related to changes in Rua (sleep vs. awake) (p < 0.05)], 2. reduced ce ntral neural drive (inspiratory phasic EMG di after 5 minutes SEH, 111 % and 121% of baseline, p < 0.05), and 3) failure to increase respirat ory frequency during SEH sleep. There was also a nonsignificant trend to a biphasic response in EMG gg and a small increase in Rua during SE H.