[Sleep and breathing at altitude of 3800 m--the acclimatization effect]

Periodic breathing (PB) is a very common phenomenon occurring during sleep at high altitude. It consists of repetitive apneas or hypopneas of central origin and clusters of hyperpneic breaths. The aim of this study was to analyze sleep structure and periodic breathing in shift workers of a gold mine situated in Tien-Schan Mountains at 3800 m. In 12 subjects aged 36.1 +/- 9.3 yrs, polysomnography (PSG) was performed twice, on the night after the first working shift or during the day following first night shift, and the second PSG at the end of the first week of work. After one week, significant increase in REM sleep was noticed (5.2 +/- 4.0% vs. 12.0 +/- 6.7%, p < 0.05). There were no differences in sleep pattern between night sleep and sleep during daytime. During first PSG periodic breathing was seen in all subjects and occupied 14.7 +/- 16.6% of total sleep time. After one week PB decreased in 8 subjects however, in 4 subjects an increase in PB was observed (15.4 +/- 11.2 vs. 29.0 +/- 11.8% of sleep time).

Sleep at altitude is characterized by reduction of REM sleep, which improves after a week of acclimatization. There are great individual variations in duration of periodic breathing; in some subjects an increase in PB can be seen.