Sleep apnea-like syndrome induced by nitrous oxide inhalation in normal men.

To study the relationship between sedation and respiration under N2O, we performed polysomnographic recordings in 15 healthy men with documented normal breathing patterns during sleep. In a first study in five subjects, we found that 50% N2O in O2 compared to 50% O2 increased sleep latency to stage 2 (59 +/- 12 vs. 17 +/- 3 min), total sleep duration (59 +/- 12 vs. 26 +/- 11 min), depth of sleep and respiratory events during sleep (18 +/- 5 vs. 1 +/- 1/h of sleep). In a second study, ten subjects were exposed to N2O (30 and 50%) in O2 during two consecutive experimental periods. Eight subjects had EEG features of physiological sleep, but nevertheless exhibited a total of 181 respiratory events. Respiratory disturbance index (RDI) during sleep was similar under 30 and 50% N2O (25 +/- 7 and 25 +/- 5/h of sleep, respectively). Obstructive events predominated, except in three subjects during N2O 30% and one during N2O 50% exposure. We conclude that N2O can induce central and obstructive sleep apneas.