title: Patients with obstructive sleep apnea syndrome benefit from acetazolamide during an altitude sojourn: a randomized, placebo-controlled, double-blind trial.
abstract: BACKGROUND
  Many patients with obstructive sleep apnea syndrome (OSA) are unable or unwilling to use continuous positive airway pressure (CPAP) therapy when traveling to the mountains for work or recreation even though they risk pronounced hypoxemia and exacerbation of sleep apnea. Because the treatment of OSA at altitude has not been established, we tested the hypothesis that acetazolamide improves hypoxemia, sleep, and breathing disturbances in otherwise untreated patients with OSA at altitude.
  
  
  METHODS
  Forty-five patients with OSA on long-term CPAP, median age 64 years, living at < 600 m underwent a placebo-controlled, double-blind, crossover trial randomized for the sequence of drug and altitude exposure (490 m, 1,860 m, and 2,590 m). Patients spent two 3-day periods at altitude and a 2-week wash-out period at < 600 m. At altitude, patients discontinued CPAP and received acetazolamide 2 × 250 mg daily or placebo. Polysomnography, vigilance, and symptoms were evaluated.
  
  
  RESULTS
  At 490 m, off CPAP, median nocturnal oxygen saturation was 93%, and the apnea/hypopnea index was 51.2/h. On placebo at 1,860 m and 2,590 m, the corresponding values were 89% and 85% and 63.6/h and 86.2/h, respectively (P < .01 vs 490 m, both instances). On acetazolamide at 1,860 m and 2,590 m, oxygen saturation was higher (91% and 88%) and apnea/hypopnea indices were lower (48.0/h and 61.4/h) than on placebo (P < .01 all instances). Acetazolamide reduced nocturnal transcutaneous Pco(2), improved sleep efficiency and subjective insomnia, and prevented excessive BP elevations at altitude.
  
  
  CONCLUSIONS
  In patients with OSA discontinuing CPAP during an altitude sojourn, acetazolamide improves oxygenation, breathing disturbances, and sleep quality by stimulating ventilation. Therefore, patients with OSA may benefit from acetazolamide at altitude if CPAP therapy is not feasible.
  
  
  BACKGROUND
  ClinicalTrials.gov; No.: NCT00714740; URL: www.clinicaltrials.gov.
authors.affiliation: Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Nussbaumer-Ochsner
authors.affiliation: Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich.
authors.forename: Tsogyal D
authors.initials: TD
authors.lastname: Latshang
authors.affiliation: Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich.
authors.forename: Silvia
authors.initials: S
authors.lastname: Ulrich
authors.affiliation: Center for Human Integrative Physiology, University of Zurich, Zurich.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Kohler
authors.affiliation: Pulmonary Division, Cantonal Hospital Munsterlingen, Munsterlingen, Switzerland.
authors.forename: Robert
authors.initials: R
authors.lastname: Thurnheer
authors.affiliation: Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich. Electronic address: konrad.bloch@usz.ch.
authors.forename: Konrad E
authors.initials: KE
authors.lastname: Bloch
mesh_terms: D000086:Acetazolamide / Q000008:administration & dosage / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000531:Altitude; D001785:Blood Gas Monitoring, Transcutaneous; D002257:Carbonic Anhydrase Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000209:etiology / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D017286:Polysomnography; D012890:Sleep / Q000187:drug effects / Q000502:physiology*; D020181:Sleep Apnea, Obstructive / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D055815:Young Adult
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D000086:Acetazolamide