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Central and obstructive sleep apnoea during ascent to high altitude
Author(s) -
BURGESS Keith R.,
JOHNSON Pamela L.,
EDWARDS Natalie
Publication year - 2004
Publication title -
respirology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 85
eISSN - 1440-1843
pISSN - 1323-7799
DOI - 10.1111/j.1440-1843.2004.00576.x
Subject(s) - medicine , effects of high altitude on humans , polysomnography , hypoxic ventilatory response , acclimatization , altitude (triangle) , anesthesia , sleep (system call) , analysis of variance , rapid eye movement sleep , cardiology , respiratory system , apnea , ophthalmology , eye movement , anatomy , operating system , botany , geometry , mathematics , biology , computer science
Objective: The aim of the study was to investigate the relationship between central sleep apnoea (CSA) at high altitude and arterial blood gas tensions, and by inference, ventilatory responsiveness. Methodology: Fourteen normal adult volunteers were studied by polysomnography during sleep, and analysis of awake blood gases during ascent over 12 days from sealevel to 5050 m in the Nepal Himalayas. Results: Thirteen subjects developed CSA. Linear regression analysis showed tight negative correlations between mean CSA index and mean values for sleep SaO 2 , PaCO 2 and PaO 2 over the six altitudes ( r 2 ≥ 0.74 for all, P < 0.03). Paradoxically there was poor correlation between the individual data for CSA index and those parameters at the highest altitude (5050‐m) where CSA was worst ( r 2 < 0.12 for all, NS), possibly due to variation in degree of acclimatization between subjects. In addition, CSA replaced mild obstructive sleep apnoea during ascent. Obstructive sleep apnoea index fell from 5.5 ± 6.9/h in rapid eye movement sleep at sealevel to 0.1 ± 0.3/h at 5050 m ( P < 0.001, analysis of variance), while CSA index rose from 0.1 ± 0.3/h to 55.7 ± 54.4/h ( P < 0.001). Conclusion: There was a general relationship between decreasing PaCO 2 and CSA, but there were significant effects from variations in acclimatization that would make hypoxic ventilatory response an unreliable predictor of CSA in individuals.