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Original Research: Sleep Disorders |

Cerebral Oxygenation in Patients With OSACerebral Oxygenation in OSA: Effects of Hypoxia at Altitude and Impact of Acetazolamide

Silvia Ulrich, MD; Yvonne Nussbaumer-Ochsner, MD; Irena Vasic, MD; Elisabeth Hasler, MD; Tsogyal D. Latshang, MD; Malcolm Kohler, MD; Thomas Muehlemann, PhD; Martin Wolf, PhD; Konrad E. Bloch, MD, FCCP
Author and Funding Information

From the Pulmonary Division and Sleep Disorders Centre (Drs Ulrich, Nussbaumer-Ochsner, Vasic, Hasler, Latshang, Kohler, and Bloch), and the Biomedical Optics Research Laboratory, Division of Neonatology (Drs Muehlemann and Wolf), University Hospital Zurich; and the Zurich Centre for Human Integrative Physiology and Zurich Centre for Interdisciplinary Sleep Research (Drs Kohler and Bloch), University of Zurich, Zurich, Switzerland.

CORRESPONDENCE TO: Konrad E. Bloch, MD, FCCP, Pulmonary Division and Sleep Disorders Centre, University Hospital Zurich, Rämistrasse 100, CH-8091 Zurich, Switzerland; e-mail: konrad.bloch@usz.ch


Drs Ulrich and Nussbaumer-Ochsner share first authorship of this manuscript.

FUNDING/SUPPORT: Grant support was provided by the Swiss National Science Foundation and by the Zurich Lung League.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;146(2):299-308. doi:10.1378/chest.13-2967
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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.

TRIAL REGISTRY:  ClinicalTrials.gov; No.: NCT00714740; URL: www.clinicaltrials.gov

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