title: Exacerbation of sleep apnoea by frequent central events in patients with the obstructive sleep apnoea syndrome at altitude: a randomised trial.
abstract: 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. ClinicalTrials.gov identifier NCT00514826.
authors.affiliation: Pulmonary Division, University Hospital of Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Nussbaumer-Ochsner
authors.forename: Nicole
authors.initials: N
authors.lastname: Schuepfer
authors.forename: Silvia
authors.initials: S
authors.lastname: Ulrich
authors.forename: Konrad E
authors.initials: KE
authors.lastname: Bloch
mesh_terms: D000368:Aged; D000531:Altitude; D001334:Automobile Driving; D002940:Circadian Rhythm; D003198:Computer Simulation; D045422:Continuous Positive Airway Pressure; D018592:Cross-Over Studies; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D017286:Polysomnography / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology* / Q000523:psychology / Q000628:therapy
chemical_list: D010100:Oxygen