title: Continuous positive airway pressure improves exercise capacity and heart rate recovery in obstructive sleep apnea.
abstract: BACKGROUND
  There is a relationship between obstructive sleep apnea (OSA) and heart failure (HF). Peak oxygen consumption (peak VO(2)), heart rate recovery, and N-terminal-pro-BNP (NT-proBNP) are strong prognostic predictors in HF. The effects of nasal continuous positive airway pressure (nCPAP) on these parameters in OSA patients are not well defined.
  
  
  METHODS
  Forty patients with newly diagnosed OSA [apnea-hypopnea index (AHI) 37 (20-65) h(-1)] underwent cardiopulmonary exercise testing for assessment of peak VO(2) and heart rate recovery at one (HRR-1) and two (HRR-2) minutes after exercise termination as well as NT-proBNP measurement at baseline and after 7.9+/-1.4 months of effective nCPAP (nightly usage>3.5 h). The effects of nCPAP were compared in patients with mild-to-moderate (AHI<30 h(-1); n=16) vs. severe (AHI>or=30 h(-1); n=24) OSA.
  
  
  RESULTS
  In the group as a whole, peak VO(2) (baseline: 31.9+/-9.3 vs. follow-up: 33.7+/-9.0 ml/kg/min; p=0.02) and HRR-2 [38 (32-43) vs. 42 (32-47) bpm; p=0.01] but not HRR-1 [22 (15-26) vs. 22 (16-27) bpm; p=0.16] improved from baseline to follow-up. The effect on peak VO(2) was mainly driven by a trend towards an increase in patients with mild-to-moderate OSA (31.8+/-10.7 vs. 33.9+/-10.2 ml/kg/min; p=0.08), whereas an effect on HRR-1 [20 (15-23) vs. 21 (16-26) bpm; p=0.03] and HRR-2 [38 (29-42) vs. 42 (33-47) bpm; p=0.004] was observed only in those with severe OSA. NT-proBNP levels remained unchanged [21 (11-45) vs. 26 (5-52) pg/ml; p=0.6].
  
  
  CONCLUSIONS
  Treatment with nCPAP is associated with an improvement in peak VO(2) and heart rate recovery in patients with OSA.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Kantonsspital St. Gallen, Switzerland. micha.maeder@baker.edu.au
authors.forename: Micha T
authors.initials: MT
authors.lastname: Maeder
authors.forename: Peter
authors.initials: P
authors.lastname: Ammann
authors.forename: Thomas
authors.initials: T
authors.lastname: Münzer
authors.forename: Otto D
authors.initials: OD
authors.lastname: Schoch
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Korte
authors.forename: Christoph
authors.initials: C
authors.lastname: Hürny
authors.forename: Jonathan
authors.initials: J
authors.lastname: Myers
authors.forename: Hans
authors.initials: H
authors.lastname: Rickli
mesh_terms: D016022:Case-Control Studies; D045422:Continuous Positive Airway Pressure; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000097:blood; D010100:Oxygen / Q000378:metabolism; D010446:Peptide Fragments / Q000097:blood; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology / Q000628:therapy*
chemical_list: D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain; D010100:Oxygen