title: Cerebral oxygenation in patients with OSA: effects of hypoxia at altitude and impact of acetazolamide.
abstract: BACKGROUND
  Sleep-disordered breathing may impair cerebral oxygenation in patients with OSA syndrome, in particular during altitude travel. We studied cerebral tissue oxygenation (CTO) at low and moderate altitude in patients with OSA and evaluated whether acetazolamide improved CTO.
  
  
  METHODS
  Eighteen patients with OSA living at < 600 m discontinued CPAP therapy during studies in Zurich (490 m) and during two sojourns of 3 days in the Swiss Alps (2 days at 1,860 m and 1 day at 2,590 m) separated by a 2-week washout period at < 600 m. Patients received acetazolamide (2 × 250 mg/d) or placebo at altitude in a randomized, double-blind, crossover design. Nocturnal polysomnography, including CTO monitoring by near-infrared spectroscopy (NIRS), was performed.
  
  
  RESULTS
  At 490 m, medians of CTO, peripheral oxygen saturation as measured by pulse oximetry (Spo2), and apnea/hypopnea index were 65%, 93%, and 57.3/h, respectively. At 2,590 m, on placebo, the corresponding values were 59%, 86%, and 86.4/h, respectively (P < .05, all corresponding comparisons). Acetazolamide increased CTO and Spo2 at 2,590 m by mean values of 2% (95% CI, 0%-4%) and 2% (95% CI, 1%-3%), respectively, and reduced the apnea/hypopnea index by 23.4/h (95% CI, 14.0-32.8/h) (P < .05, all changes). Cerebral total hemoglobin concentration, a NIRS-derived surrogate reflecting regional cerebral blood volume, increased by a similar degree in response to apneas at 490 m and 2,590 m and during acetazolamide and placebo treatment.
  
  
  CONCLUSIONS
  In patients with OSA staying at altitude, nocturnal cerebral and arterial oxygenation were reduced in association with exacerbated sleep apnea. Acetazolamide partially improved CTO, Spo2, and sleep apnea without impairing the cerebral blood flow response to apneas.
  
  
  BACKGROUND
  ClinicalTrials.gov; No.: NCT00714740; URL: www.clinicaltrials.gov.
authors.affiliation: Pulmonary Division and Sleep Disorders Centre, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Silvia
authors.initials: S
authors.lastname: Ulrich
authors.affiliation: Pulmonary Division and Sleep Disorders Centre, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Nussbaumer-Ochsner
authors.affiliation: Pulmonary Division and Sleep Disorders Centre, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Irena
authors.initials: I
authors.lastname: Vasic
authors.affiliation: Pulmonary Division and Sleep Disorders Centre, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Hasler
authors.affiliation: Pulmonary Division and Sleep Disorders Centre, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Tsogyal D
authors.initials: TD
authors.lastname: Latshang
authors.affiliation: Pulmonary Division and Sleep Disorders Centre, University Hospital Zurich, Zurich, Switzerland; Zurich Centre for Human Integrative Physiology and Zurich Centre for Interdisciplinary Sleep Research, University of Zurich, Zurich, Switzerland.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Kohler
authors.affiliation: Biomedical Optics Research Laboratory, Division of Neonatology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Muehlemann
authors.affiliation: Biomedical Optics Research Laboratory, Division of Neonatology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Wolf
authors.affiliation: Pulmonary Division and Sleep Disorders Centre, University Hospital Zurich, Zurich, Switzerland; Zurich Centre for Human Integrative Physiology and Zurich Centre for Interdisciplinary Sleep Research, University of Zurich, Zurich, Switzerland. Electronic address: konrad.bloch@usz.ch.
authors.forename: Konrad E
authors.initials: KE
authors.lastname: Bloch
mesh_terms: D000086:Acetazolamide / Q000008:administration & dosage* / Q000493:pharmacokinetics; D000328:Adult; D000368:Aged; D000531:Altitude; D000532:Altitude Sickness / Q000150:complications / Q000378:metabolism / Q000503:physiopathology*; D002257:Carbonic Anhydrase Inhibitors / Q000008:administration & dosage / Q000493:pharmacokinetics; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010101:Oxygen Consumption; D018579:Patient Selection; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000378:metabolism / Q000628:therapy*; D019265:Spectroscopy, Near-Infrared; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D000086:Acetazolamide