Effects of Five Nights under Normobaric Hypoxia on Sleep Quality.
OBJECTIVE
The purpose of this study was to evaluate the effects of five nights' sleep under normobaric hypoxia on ventilatory acclimatization and sleep quality.


METHODS
Seven men initially slept for six nights under normoxia and then for five nights under normobaric hypoxia equivalent to a 2000-m altitude. Nocturnal polysomnograms (PSGs), arterial blood oxygen saturation (SpO2), and respiratory events were recorded on the first and fifth nights under both conditions.


RESULTS
The hypoxic ventilatory response (HVR), hypercapnic ventilatory response (HCVR), and resting end-tidal CO2 (resting PETCO2) were measured three times during the experimental period. The duration of slow-wave sleep (SWS: stage N3) and the whole-night delta (1-3 Hz) power of nonrapid eye movement (NREM) sleep EEG decreased on the first night under hypoxia. This hypoxia-induced sleep quality deterioration on the first night was accompanied by a lower mean and minimum SpO2, a longer time spent with SpO2 below 90% (<90% SpO2 time), and more episodes of respiratory disturbance. On the fifth night, the SWS duration and whole-night delta power did not differ between the conditions. Although the mean SpO2 under hypoxia was still lower than under normoxia, the minimum SpO2 increased, and the <90% SpO2 time and number of episodes of respiratory disturbance decreased during the five nights under hypoxia. The HVR increased and resting PETCO2 decreased after five nights under hypoxia.


CONCLUSIONS
The results suggest that five nights under hypoxia improves the sleep quality. This may be derived from improvements of respiratory disturbances, the minimum SpO2, and <90% SpO2 time.
1Department of Sports Sciences, Japan Institute of Sports Sciences, Nishigaoka, Kita-ku, Tokyo, JAPAN; 2Faculty of Sport Sciences, Waseda University, Mitakajima, Tokorozawa, Saitama, JAPAN; 3Director General, Japan Institute of Sports Sciences, Nishigaoka, Kita-ku, Tokyo, JAPAN.
Masako
M
Hoshikawa
Sunao
S
Uchida
Takuya
T
Osawa
Kazumi
K
Eguchi
Takuma
T
Arimitsu
Yasuhiro
Y
Suzuki
Takashi
T
Kawahara
D000222:Adaptation, Physiological; D002245:Carbon Dioxide / Q000378:metabolism; D004562:Electrocardiography; D004569:Electroencephalography; D004576:Electromyography; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000097:blood; D017286:Polysomnography; D012890:Sleep / Q000502:physiology*; D012891:Sleep Apnea Syndromes / Q000503:physiopathology; D055815:Young Adult
D002245:Carbon Dioxide; D010100:Oxygen