title: Heart rate recovery post 6-minute walking test in obstructive sleep apnea: cycle ergometry versus 6-minute walking test in OSA patients.
abstract: OBJECTIVE
  To examine the clinical usefulness of heart rate recovery (HRR) post 6-minute walking test (6MWT) as a simple marker of cardiovascular risk in obstructive sleep apnea (OSA) patients in comparison to HRR post cycle ergometry, the validated and more sophisticated protocol.
  
  
  METHODS
  Seventy-four participants underwent full overnight polysomnography, cycle ergometry and 6MWT. The HRR at 1, 2 and 3 min (HRR-1, HRR-2 and HRR-3) 6MWT was compared to HRR at 1, 2, and 3 min post cycle ergometry in normal subjects and in moderate and severe OSA patients before and after 6-month CPAP treatment.
  
  
  RESULTS
  The HRR-1, HRR-2 and HRR-3 in 6MWT were significantly different between normal, moderate and severe OSA patients with higher rates achieved in normal. The higher the severity of OSA the lower the HRR was. There were also no differences found between work rate and distance walked during cycle ergometry or 6MWT, respectively, concerning normal, moderate and severe OSA patients. Heart rate recovery was further associated with minimum saturation of oxygen during sleep independently of the duration of apnea episodes of BMI and ESS. The treatment with CPAP had a beneficial effect on HRR both post-6MWT and post cycle ergometry.
  
  
  CONCLUSIONS
  Autonomic nervous system dysfunction in OSA can be found even with submaximal exertion. Heart rate recovery post-6MWT, such as HRR post cycle ergometry, was significantly impaired in OSA patients in comparison to normals and was favorably influenced from CPAP treatment. Furthermore, it was found to be more sensitive compared with distance walked in 6MWT in discriminating severity of OSA. The HRR post-6MWT was found to be an easily measured and reliable marker of OSA severity both before and after CPAP treatment.
authors.affiliation: 1st Respiratory Medicine Department, National and Kapodistrian University of Athens, Medical School, "Sotiria" Chest Diseases Hospital, Athens, Greece, kg.cholidou@yahoo.gr.
authors.forename: Kyriaki G
authors.initials: KG
authors.lastname: Cholidou
authors.forename: Effrosyni D
authors.initials: ED
authors.lastname: Manali
authors.forename: Fotis
authors.initials: F
authors.lastname: Kapsimalis
authors.forename: Ioannis D
authors.initials: ID
authors.lastname: Kostakis
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Vougas
authors.forename: Davina
authors.initials: D
authors.lastname: Simoes
authors.forename: Evaggelos
authors.initials: E
authors.lastname: Markozannes
authors.forename: Ioannis
authors.initials: I
authors.lastname: Vogiatzis
authors.forename: Petros
authors.initials: P
authors.lastname: Bakakos
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Koulouris
authors.forename: Manos
authors.initials: M
authors.lastname: Alchanatis
mesh_terms: D000328:Adult; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D020127:Recovery of Function / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D016138:Walking