title: Sleep-Disordered Breathing and Vascular Function in Patients With Chronic Mountain Sickness and Healthy High-Altitude Dwellers.
abstract: 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.
  
  
  BACKGROUND
  ClinicalTrials.gov; No.: NCT01182792; URL: www.clinicaltrials.gov.
authors.affiliation: Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Emrush
authors.initials: E
authors.lastname: Rexhaj
authors.affiliation: Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Stefano F
authors.initials: SF
authors.lastname: Rimoldi
authors.affiliation: Institute of Clinical Physiology, Pisa, Italy.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Pratali
authors.affiliation: Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Roman
authors.initials: R
authors.lastname: Brenner
authors.affiliation: Center for Investigation and Research in Sleep, Lausanne-CHUV, Switzerland.
authors.forename: Daniela
authors.initials: D
authors.lastname: Andries
authors.affiliation: Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Soria
authors.affiliation: Instituto Boliviano de Biologia de Altura, La Paz, Bolivia.
authors.forename: Carlos
authors.initials: C
authors.lastname: Salinas
authors.affiliation: Instituto Boliviano de Biologia de Altura, La Paz, Bolivia.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Villena
authors.affiliation: Instituto Boliviano de Biologia de Altura, La Paz, Bolivia.
authors.forename: Catherine
authors.initials: C
authors.lastname: Romero
authors.affiliation: Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Yves
authors.initials: Y
authors.lastname: Allemann
authors.affiliation: Center for Investigation and Research in Sleep, Lausanne-CHUV, Switzerland.
authors.forename: Alban
authors.initials: A
authors.lastname: Lovis
authors.affiliation: Center for Investigation and Research in Sleep, Lausanne-CHUV, Switzerland.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Heinzer
authors.affiliation: Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland; Department of Internal Medicine, Lausanne-CHUV, Switzerland.
authors.forename: Claudio
authors.initials: C
authors.lastname: Sartori
authors.affiliation: Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland; Facultad de Ciencias, Departamento de Biología, Universidad de Tarapacá, Arica, Chile. Electronic address: urs.scherrer2@insel.ch.
authors.forename: Urs
authors.initials: U
authors.lastname: Scherrer
mesh_terms: D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000453:epidemiology* / Q000503:physiopathology; D001794:Blood Pressure; D001838:Bolivia / Q000453:epidemiology; D016022:Case-Control Studies; D002908:Chronic Disease; D017548:Echocardiography, Transesophageal; D054092:Foramen Ovale, Patent / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000503:physiopathology; D006801:Humans; D006976:Hypertension, Pulmonary / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000503:physiopathology; D000860:Hypoxia / Q000453:epidemiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000453:epidemiology* / Q000503:physiopathology
keywords: chronic mountain sickness; high altitude; pulmonary artery pressure; sleep-disordered breathing; vascular function