The quality of sleep and periodic breathing in healthy subjects at an altitude of 3,200 m.

The medical risks of travel and stay at high altitude are well known. Many more people travel for recreation to lower but still significant altitudes. To investigate the quality of sleep and sleep-related breathing disorders (SRBD) at that altitude we performed full polysomnography in nine young volunteers at lowland (760 m above sea level) on the first and sixth night after ascent to 3,200 m. There have been few studies on such populations. The subjects were nonsmoking healthy males aged 20.3 +/- 3.5 years with normal spirometry and arterial blood gas measurements performed at low altitude. Although there was no statistically significant difference in the duration of stages and sleep quality between low altitude night and both nights at high altitude as assessed by percent of sleep spent in stage 1, 2, 3+4 NREM, and REM sleep, total sleep time (TST), and sleep efficiency; the number of arousals and awakenings doubled at high altitude. There was no periodic breathing (PB) during sleep, except in isolated central events of SRBD, at low altitude. PB appeared at altitude mostly during NREM sleep and its intensity remained stable throughout the study period. Individual variations of PB intensity were high, ranging from 0.1 to 24% of TST. There were also some episodes of obstructive apnea and hypopnea during sleep at high altitude (p < 0.001). Mean SaO2 was lower during the study nights at high altitude when compared with low altitude. There were some signs of ventilatory acclimatization as shown by a higher mean SaO2 during the sixth compared with the first night at altitude (p < 0.001). We conclude that the sleep quality at the altitude of 3,200 m remains satisfactory when compared to low altitude. There is high individual variability in intensity of PB at that altitude.