EFFECT OF ZOLPIDEM ON SLEEP AND VENTILATORY PATTERNS AT SIMULATED ALTITUDE OF 4,000 METERS

The purpose of this study was to assess the effect of zolpidem 10 mg, a new imidazopyridine hypnotic drug, on sleep and respiratory patterns at a simulated altitude of 4,000 meters. Eight male subjects spent th ree nights in a decompression chamber. The first study night was spent at the ambient pressure corresponding to sea level. The two other nig hts were spent at a simulated altitude of 4,000 meters with either zol pidem or a placebo in random order according to a double-blind, crosso ver design. All subjects showed periodic breathing (PB) during sleep a t simulated high altitude. Furthermore, altitude was associated with d ecreases in total sleep time (TST), slow-wave sleep (SWS), and REM sle ep, and with significant increases in Stage 1 duration and in the arou sal index. Most arousals were synchronous with the hyperpneic phase of PB. The main finding of our study is that zolpidem improved sleep cha racteristics at high altitude, inducing a decrease in sleep onset late ncy (placebo, 22 +/- 12 min versus zolpidem, 10 +/- 6 min), an increas e in SWS duration (placebo, 46 +/- 28 min versus zolpidem, 69 +/- 28 m in), and a reduction in the arousal index during SWS (placebo, 7.4 +/- 4.1 per h versus zolpidem: 2.4 +/- 1.0 per h). Furthermore, none of t he respiratory parameters were significantly affected by zolpidem in a ny sleep stage. in conclusion, zolpidem improved sleep quality at high altitude without adversely affecting respiration.