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Original Research: Sleep Disorders |

Sleep-Disordered Breathing and Vascular Function in Patients With Chronic Mountain Sickness and Healthy High-Altitude Dwellers

Emrush Rexhaj, MD; Stefano F. Rimoldi, MD; Lorenza Pratali, MD; Roman Brenner, MD; Daniela Andries, BS; Rodrigo Soria, MD; Carlos Salinas, MD; Mercedes Villena, MD; Catherine Romero, BS; Yves Allemann, MD; Alban Lovis, MD; Raphaël Heinzer, MD; Claudio Sartori, MD; Urs Scherrer, MD
Author and Funding Information

Drs Heinzer, Sartori, and Scherrer contributed equally to this manuscript.

FUNDING/SUPPORT: This work was supported by grants from the Swiss National Science Foundation and the Placide Nicod Foundation.

CORRESPONDENCE TO: Urs Scherrer, MD, Swiss Cardiovascular Center Bern, University Hospital, Bern, Switzerland CH-3010


Copyright 2016, American College of Chest Physicians. All Rights Reserved.


Chest. 2016;149(4):991-998. doi:10.1378/chest.15-1450
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Background  Chronic mountain sickness (CMS) is often associated with vascular dysfunction, but the underlying mechanism is unknown. Sleep-disordered breathing (SDB) frequently occurs at high altitude. At low altitude, SDB causes vascular dysfunction. Moreover, in SDB, transient elevations of right-sided cardiac pressure may cause right-to-left shunting in the presence of a patent foramen ovale (PFO) and, in turn, further aggravate hypoxemia and pulmonary hypertension. We speculated that SDB and nocturnal hypoxemia are more pronounced in patients with CMS compared with healthy high-altitude dwellers, and are related to vascular dysfunction.

Methods  We performed overnight sleep recordings, and measured systemic and pulmonary artery pressure in 23 patients with CMS (mean ± SD age, 52.8 ± 9.8 y) and 12 healthy control subjects (47.8 ± 7.8 y) at 3,600 m. In a subgroup of 15 subjects with SDB, we assessed the presence of a PFO with transesophageal echocardiography.

Results  The major new findings were that in patients with CMS, (1) SDB and nocturnal hypoxemia was more severe (P < .01) than in control subjects (apnea-hypopnea index [AHI], 38.9 ± 25.5 vs 14.3 ± 7.8 number of events per hour [nb/h]; arterial oxygen saturation, 80.2% ± 3.6% vs 86.8% ± 1.7%, CMS vs control group), and (2) AHI was directly correlated with systemic blood pressure (r = 0.5216; P = .001) and pulmonary artery pressure (r = 0.4497; P = .024). PFO was associated with more severe SDB (AHI, 48.8 ± 24.7 vs 14.8 ± 7.3 nb/h; P = .013, PFO vs no PFO) and hypoxemia.

Conclusions  SDB and nocturnal hypoxemia are more severe in patients with CMS than in control subjects and are associated with systemic and pulmonary vascular dysfunction. The presence of a PFO appeared to further aggravate SDB. Closure of the PFO may improve SDB, hypoxemia, and vascular dysfunction in patients with CMS.

Trial Registry  ClinicalTrials.gov; No.: NCT01182792; URL: www.clinicaltrials.gov;

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