title: Physiological response to the 6-minute walk test in chronic heart failure patients versus healthy control subjects.
abstract: BACKGROUND
  The distance walked in 6 minutes (6MWD) has been reported to be linearly related to peak oxygen uptake (VO2) in cardiac diseases and in lung diseases. In these patients, the VO2 during a 6-min walk test (walkVO2) has been found to be nearly equivalent to peakVO2, but with a lower respiratory exchange ratio (RER). Whether these observations translate to the less functionally impaired patients or healthy control subjects is not exactly known.
  
  
  METHODS
  Thirty-two healthy control subjects and 15 chronic heart failure (CHF) patients performed a 6-min walk test and a maximal cardiopulmonary exercise test (CPET) both with measurements of gas exchange.
  
  
  RESULTS
  The 6MWD and peakVO2 were linearly correlated, but with an increased slope appearing above 532 m. In CHF patients, walkVO2 was similar to peakVO2, but with lower heart rate and ventilation than measured at peak exercise. In healthy control subjects, VO2, ventilation and heart rate were lower during the 6-min walk than at maximal exercise but higher than at the anaerobic threshold. The RER during the 6-min walk remained <1 in both groups.
  
  
  CONCLUSIONS
  Above 500 m, 6MWD becomes less sensitive to any increase in peakVO2. Furthermore, CHF patients and healthy control subjects exercise respectively at maximal and high VO2, but below the anaerobic threshold (as assessed by a CPET) during the 6-min walk test.
authors.affiliation: Faculty of Motricity Sciences, Université Libre de Bruxelles, Belgium gael.deboeck@ulb.ac.be.
authors.forename: Gaël
authors.initials: G
authors.lastname: Deboeck
authors.affiliation: Erasmus University Hospital, Université Libre de Bruxelles, Belgium.
authors.forename: Alain
authors.initials: A
authors.lastname: Van Muylem
authors.affiliation: Erasmus University Hospital, Université Libre de Bruxelles, Belgium.
authors.forename: Jean Luc
authors.initials: JL
authors.lastname: Vachiéry
authors.affiliation: Faculty of Medicine, Université Libre de Bruxelles, Belgium.
authors.forename: Robert
authors.initials: R
authors.lastname: Naeije
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002908:Chronic Disease; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D016138:Walking / Q000502:physiology*
keywords: 6-min walk test; chronic heart failure; exercise physiology; exercise testing; healthy subjects; oxygen consumption