title: Oxygen kinetics during 6-minute walk tests in patients with cardiovascular and pulmonary disease.
abstract: BACKGROUND
  The 6-Minute Walk Test (6MWT) is representative of daily-life activities and reflects the functional capacity of patients. The change of oxygen uptake (VO2) in the initial phase of low-intensity exercise (VO2 kinetics) can be used to assess submaximal exercise performance of patients.The objective of the following study was to analyse VO2 kinetics in patients with different pulmonary and cardiovascular diseases. In addition, we investigated the extent to which VO2 kinetics at the onset of the 6MWT were associated with exercise capacity, morbidity and mortality.
  
  
  METHODS
  VO2 kinetics of 204 patients and 16 healthy controls were obtained using mobile telemetric cardiopulmonary monitoring during a 6MWT. A new mean response time (MRT) index (wMRT) was developed to quantify VO2 kinetics by correcting MRT for work rate. The differences in wMRT between disease categories as well as the association between wMRT and patients' exercise capacity and outcome - time to hospitalization/death- were tested.
  
  
  RESULTS
  The assessment of a robust wMRT was feasible in 86% (244/284) patients. wMRT was increased in patients compared to healthy controls (p <0.001). wMRT was largest in patients with pulmonary arterial hypertension (PAH). There were significant associations between wMRT and exercise capacity in all patients. High wMRT was found to be associated with a high rate of death and re-hospitalization in patients with CHF (p = 0.024). In patients with pulmonary diseases and pulmonary hypertension wMRT was not associated with outcome (p = 0.952).
  
  
  CONCLUSIONS
  Submaximal exercise performance of patients is reduced. O2 kinetics at the onset of exercise are associated with exercise capacity in all patients. wMRT was found to be an important prognostic factor in patients with congestive heart failure (CHF), but not with pulmonary diseases.
authors.forename: Lukas
authors.initials: L
authors.lastname: Kern
authors.forename: Sophie
authors.initials: S
authors.lastname: Condrau
authors.forename: Florent
authors.initials: F
authors.lastname: Baty
authors.forename: Jan
authors.initials: J
authors.lastname: Wiegand
authors.forename: Arno J R
authors.initials: AJ
authors.lastname: van Gestel
authors.forename: Andrea
authors.initials: A
authors.lastname: Azzola
authors.forename: Michael
authors.initials: M
authors.lastname: Tamm
authors.affiliation: Division of Pulmonary Medicine, Hospital St, Gallen, CH-9002 St, Gallen, Switzerland. martin.brutsche@kssg.ch.
authors.forename: Martin
authors.initials: M
authors.lastname: Brutsche
mesh_terms: D000328:Adult; D000368:Aged; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006333:Heart Failure / Q000401:mortality / Q000503:physiopathology*; D006339:Heart Rate; D006760:Hospitalization; D006801:Humans; D006976:Hypertension, Pulmonary / Q000401:mortality / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000493:pharmacokinetics*; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange; D056152:Respiratory Rate; D013686:Telemetry; D013990:Tidal Volume; D016138:Walking / Q000502:physiology*
chemical_list: D010100:Oxygen