Respiratory changes and structure of sleep in young high-altitude dwellers in the Andes of Peru.

Sleep organisation in eight young [mean (SD); 20.9 (2.6) years] Peruvian high-altitude residents was studied in a laboratory in Cerro de Pasco at 4300 m. Electroencephalograms, electromyograms, electro-oculograms, electrocardiograms, respiratory movements and arterial oxygen saturation were recorded on an 8-channel Medilog recorder and analysed later in England. Haematocrits ranged from 48% to 64% [57.9 (5.6)%]. The amount of slow wave rapid eye movement (REM) sleep was similar to that reported in young lowlanders sleeping at sea level but very different to the disturbed sleep in visitors sleeping at high altitude. All the Peruvians showed episodes of periodic breathing and respiratory apnoeas [29 (15) night-1] resulting in marked arterial oxygen desaturation [81 (4.5)%; changes of 6 (2.5)%]. These events occurred either during stage 2 or REM sleep and were more frequent in those with lower haematocrits. The amount of wakefulness during the night was 2-3 times greater than would be expected in an age-matched lowland population at sea level. The awakenings were strongly associated with apnoeas (P < 0.02) but were negatively correlated with haematocrit, although this was only significant for seven of the subjects (P < 0.05).