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Exacerbation of sleep apnoea by frequent central events in patients with the obstructive sleep apnoea syndrome at altitude: a randomised trial
  1. Yvonne Nussbaumer-Ochsner1,
  2. Nicole Schuepfer1,2,
  3. Silvia Ulrich1,
  4. Konrad E Bloch1
  1. 1Pulmonary Division, University Hospital of Zurich, Zurich Center for Integrative Human Physiology, University of Zurich, Switzerland
  2. 2Institute of Human Movement Sciences and Sports, Federal Institute of Technology, Zurich, Switzerland
  1. Correspondence to Konrad E Bloch, Pulmonary Division, University Hospital of Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland; konrad.bloch{at}


Background Many patients with the obstructive sleep apnoea syndrome (OSA) travel to the mountains for recreational and professional activities while temporarily discontinuing continuous positive airway pressure (CPAP) treatment. A study was undertaken to evaluate the hypothesis that altitude would aggravate their hypoxaemia, sleep-related breathing disturbances and impair daytime performance.

Methods Thirty-four patients with OSA of median age 62 years (IQR 57–65), median apnoea/hypopnoea index (AHI) 47.5 events/h (IQR 32.4–72.8), residing at <600 m were enrolled. A crossover trial randomised for the sequence of altitude exposure was carried out: patients spent 1 day in Zurich (490 m) and 4 days in the Swiss Alps at 1860 m and 2590 m (2 days each) during which continuous positive airway pressure was discontinued. Daily evaluations included polysomnography, symptom questionnaires, physical examination and driving simulator tests.

Results Polysomnography revealed median oxygen saturations at 490 m and in the first and second nights at 1860 and 2590 m, respectively, of 94%, 90%, 90%, 86% and 87% (p<0.01 between altitudes). Corresponding median AHI were 47.5, 85.1, 74.6, 90.0 and 90.9 events/h (p<0.01 between altitudes) with ratios of central to obstructive events of 0.1, 0.8, 1.0, 1.9 and 1.9 (p<0.01 between altitudes). Tracking performance during simulated driving was significantly impaired at 2590 m compared with 490 m. Systolic blood pressure and cardiac arrhythmias were increased at altitude.

Conclusions Altitude exposure in untreated patients with OSA aggravates hypoxaemia, increases sleep-related breathing disturbances due to frequent central apnoeas/hypopnoeas, impairs driving simulator performance and induces cardiovascular stress. These findings have implications for counselling and treating patients with OSA planning to travel to high altitude. identifier NCT00514826.

  • Hypoxia
  • sleep apnoea
  • control of breathing
  • periodic breathing
  • altitude

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  • Funding Swiss National Science Foundation, Lung Leagues of Zurich and of Schaffhausen, Switzerland.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the ethics committee of the University Hospital of Zurich.

  • Provenance and peer review Not commissioned; externally peer reviewed.