title: Effects of obstructive sleep apnea on hemodynamic parameters in patients entering cardiac rehabilitation.
abstract: OBJECTIVE
  Obstructive sleep apnea (OSA) is a prevalent form of sleep-disordered breathing. Evidence suggests that OSA may lead to cardiac remodeling, although the literature is equivocal. Previous literature suggests a high percentage of individuals entering a cardiac rehabilitation (CR) program also have OSA. The objective of this study was to determine whether resting hemodynamic variables were altered in OSA subjects entering CR compared with those without OSA, as determined by impedance cardiography.
  
  
  METHODS
  Subjects entering an early outpatient CR program were screened for OSA using an at-home screening device and verified by a sleep physician. Subjects were divided into an OSA group (n = 48) or a control group (n = 25) on the basis of the screening results. Hemodynamic variables were measured during supine rest using impedance cardiography. A 6-minute walk test was performed to assess functional capacity.
  
  
  RESULTS
  The proportion of cardiac diagnoses was similar between groups. Overall, 66% of the subjects were positive for OSA. Subject groups did not differ by age, body mass index, heart rate, diastolic blood pressure, or functional capacity. Cardiac output, cardiac index, stroke volume, contractility index, and left cardiac work index were all significantly decreased in the OSA group compared with the control group (P < .05).
  
  
  CONCLUSIONS
  Findings suggest that OSA results in decreased cardiac function in patients entering CR, likely because of pressure and volume changes associated with apneic events. This may place those individuals at a disadvantage in recovering from their cardiac event, and place them at increased risk for secondary complications.
authors.affiliation: Department of Kinesiology, James Madison University, Harrisonburg, Virginia (Dr Hargens and Ms Shafer); Departments of Physical Therapy (Dr Aron) and Health and Human Performance (Dr Newsome), Radford University, Radford, Virginia; Department of Cardiac Rehabilitation, Carilion Clinic, Roanoke, Virginia (Dr Austin); and Department of Kinesiology and Nutrition (Ms Shafer), University of Illinois at Chicago.
authors.forename: Trent A
authors.initials: TA
authors.lastname: Hargens
authors.forename: Adrian
authors.initials: A
authors.lastname: Aron
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Newsome
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Austin
authors.forename: Brooke M
authors.initials: BM
authors.lastname: Shafer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D000072038:Cardiac Rehabilitation; D002307:Cardiography, Impedance; D002318:Cardiovascular Diseases / Q000150:complications / Q000503:physiopathology; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000503:physiopathology*; D013318:Stroke Volume / Q000502:physiology