Abstract
Background: The course of acclimatization at high altitude over several weeks is not extensively studied. We performed repeated physiological assessments in healthy lowlanders staying for 3 weeks at 3200m.
Methods: 16 healthy volunteers (23-33y) underwent sleep studies during 1 night in Bishkek (760m), and during nights 1, 7 and 21 at Tuja-Ashu (3200m), Kyrgyzstan. Reaction time (psychomotor vigilance test), postural control (center of gravity displacement on balance board) and subjective sleep quality (visual analog scale, 0-100 with increasing quality) were assessed.
Results: Compared to 760m, mean nocturnal oxygen saturation dropped in the first night at 3200m and increased subsequently. Postural control worsened over more than a week and recovered after 21 day. Reaction time and subjective sleep quality were not affected.
760m | 3200m (Night 1) | 3200m (Night 7) | 3200m (Night 21) | |
Mean nocturnal SpO2, % | 95 (94;97) | 86* (85;89) | 89* § (87;90) | 90* § ∞ (88;91) |
Nocturnal oxygen desaturation index, 1/h | 1.0 (0.3;2.2) | 6.5* (4.5;12.1) | 5.7* § (3.6;8.7) | 6.4* (4.2;11.1) |
Subjective sleep quality, % | 70 (48;77) | 55 (27;79) | 73 (46;84) | 63 (45;81) |
Reaction time, ms | 226 (212;231) | 236 (210;259) | 237 (212;244) | 228 (212;246) |
Center of gravity displacement, cm | 24.7 (22.4;26.1) | 26.9* (25.1;28.6) | 28.0* (25.1;29.5) | 26.6 (23.6;29.1) |
Medians (quartiles); * p<0.05 vs. 760m; § p<0.05 vs. Night 1, 3200m; ∞ p<0.05 vs. Night 7, 3200m.
Conclusion: In healthy lowlanders staying at 3200m respiratory acclimatization extends over at least 3 weeks. Hypoxia impairs postural control for at least one week while reaction time and subjective sleep quality are not measurably affected despite persistent mild nocturnal periodic breathing.
- Copyright ©the authors 2016