title: The impact of CPAP on cardiovascular biomarkers in minimally symptomatic patients with obstructive sleep apnea: a pilot feasibility randomized crossover trial.
abstract: BACKGROUND
  Previous, largely uncontrolled studies demonstrated the substantial effects of continuous positive airway pressure ventilation (CPAP) on a variety of physiologic and biochemical markers known to be risk factors for cardiovascular disease in patients with obstructive sleep apnea (OSA). In this pilot crossover study, we assessed (1) the feasibility of using CPAP in a group of minimally symptomatic patients with OSA, assessed through patient compliance and (2) CPAP therapy's effect on biomarkers in these patients.
  
  
  METHODS
  We studied patients with minimal daytime sleepiness who were referred to the University of British Columbia's Hospital Sleep Clinic with suspected OSA and an apnea-hypopnea index (AHI) > 15 events/h. Patients were randomized to either CPAP or no therapy for 4 weeks followed by a washout of 4 weeks, and then a crossover to the other intervention. Fasting morning blood and urine, 24-h blood pressure (BP) measurements, and endothelial function (peak flow-mediated dilation to nitroglycerin-mediated dilation ratio) were assessed before and after each study intervention.
  
  
  RESULTS
  Nine adult male and four female patients were studied. Mean (SD) age was 55 (7) years, mean AHI = 27.9/h, mean Epworth Sleepiness Score = 6.8 (11/13 had a score < 10), and mean BMI = 31.1 kg/m(2). Mean compliance with CPAP therapy was 5.53 h/night. Compared to no therapy, potential improvements were observed with CPAP for urinary microalbumin, norepinephrine, and epinephrine to creatinine ratios (decreased by 3.51 mg/mmol, 1.70 nmol/mmol, and 0.95 nmol/mmol, respectively); 24-h BP (systolic decreased by 3.60 mmHg, diastolic by 0.70 mmHg); homeostasis model for insulin resistance score (decreased by 1.11); and endothelial function (increased by 7.4%). However, none of the above differences was significant (p > 0.10).
  
  
  CONCLUSIONS
  In this pilot study there were potential improvements in a variety of cardiovascular biomarkers with CPAP. CPAP compliance was reasonably good even though patients were not particularly sleepy. Accordingly, larger randomized controlled trials in this area appear feasible and warranted.
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Vikram R
authors.initials: VR
authors.lastname: Comondore
authors.forename: Rupi
authors.initials: R
authors.lastname: Cheema
authors.forename: Joel
authors.initials: J
authors.lastname: Fox
authors.forename: Arsalan
authors.initials: A
authors.lastname: Butt
authors.forename: G B
authors.initials: GB
authors.lastname: John Mancini
authors.forename: John A
authors.initials: JA
authors.lastname: Fleetham
authors.forename: C Frank
authors.initials: CF
authors.lastname: Ryan
authors.forename: Sammy
authors.initials: S
authors.lastname: Chan
authors.forename: Najib T
authors.initials: NT
authors.lastname: Ayas
mesh_terms: D000419:Albuminuria / Q000652:urine*; D015415:Biomarkers / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology; D002097:C-Reactive Protein / Q000378:metabolism*; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000378:metabolism* / Q000503:physiopathology; D002395:Catecholamines / Q000652:urine*; D045422:Continuous Positive Airway Pressure; D018592:Cross-Over Studies; D004837:Epinephrine / Q000652:urine; D005260:Female; D006801:Humans; D008055:Lipids / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000652:urine; D010865:Pilot Projects; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000378:metabolism* / Q000503:physiopathology / Q000628:therapy
chemical_list: D015415:Biomarkers; D002395:Catecholamines; D008055:Lipids; D002097:C-Reactive Protein; D009638:Norepinephrine; D004837:Epinephrine
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