BREATHING DURING WAKEFULNESS AND NREM SLEEP IN HUMANS WITHOUT AN UPPER AIRWAY

The increase in PCO2 that occurs during sleep may reflect an inadequat e ventilatory compensation to an increase in upper airway resistance. To address this question in humans, we examined changes in breathing d uring wakefulness and non-rapid-eye-movement sleep In eight laryngecto mized subjects who breathed through a tracheal stoma. In these subject s, any sleep-related Increase in upper airway resistance could not aff ect ventilation. Healthy subjects breathing via an intact upper airway were studied as controls. The mean increase in end-tidal PCO2 from wa kefulness to sleep was 2.7 +/- 2.6 (SD) Torr (P = 0.05) in laryngectom ized subjects and 1.6 +/- 1.4 Torr (P = 0.02) in control subjects. Dur ing wakefulness, ventilation was lower in laryngectomized subjects com pared with control subjects, although this difference was not statisti cally significant (6.8 +/- 1.9 vs. 7.4 +/- 1.2 1/min; P > 0.05). Durin g sleep, tile fall in ventilation was similar in the two groups (1.1 /- 2.1 vs. 0.8 +/- 2.1 l/min; P > 0.05). Our observations are not cons istent with the view that increases in upper airway resistance are obl igatory for sleep-related CO2 retention in humans.