title: The relationship of the 6-min walk test to maximal oxygen consumption in transplant candidates with end-stage lung disease.
abstract: OBJECTIVE
  To assess the relationship of distance ambulated during the 6-min walk test (6'WT) to maximal oxygen consumption (VO2 max).
  
  
  METHODS
  Multivariate analysis of patient characteristics to VO2 max.
  
  
  METHODS
  Pre-lung transplant evaluation.
  
  
  METHODS
  60 patients (22 men, 38 women; mean age, 44 years) with end-stage lung disease (mean FEV1 and forced vital capacity of 0.97 and 1.93, respectively).
  
  
  RESULTS
  The 6'WT was performed on a level hallway surface, and VO2 max was obtained during maximal cycle ergometry exercise testing with respiratory gas analysis. Multivariate analysis of patient characteristics (age, sex, weight, FEV1, FVC, diffusing capacity for carbon monoxide (DCO), 6'WT distance ambulated, number of rests per 6'WT, and the maximal heart rate, blood pressure, rate-pressure product, respiratory rate, oxygen saturation, rating of perceived exertion, and amount of supplemental oxygen used during the 6'WT) was performed on two groups of 30 patients each (group A or B) who were randomly assigned to either group by a process of random selection using a computer-generated random numbers program. Distance ambulated was the strongest independent predictor of VO2 max (r = 0.73; p < 0.0001) in both groups, and adding age, weight, and pulmonary function test results (FVC, FEV1, and DCO) to the regression equation increased the correlation coefficient to 0.83. Because of the significant correlation of distance ambulated during the 6'WT to VO2 max, the prediction equation obtained from the multivariate analysis of group A, VO2 max = 0.006 x distance (feet) +3.38, was used to estimate the VO2 max of the group B patients. No significant difference was observed between the estimated (x +/- SD = 8.9 +/- 2.4 mL/kg/min) and observed (x +/- SD = 9.4 +/- 3.8 mL/kg/min) VO2 max (mean difference, 0.5 mL/kg/min; SD of the difference = 2.88).
  
  
  CONCLUSIONS
  The distance ambulated during a 6'WT can predict VO2 max in patients with end-stage lung disease. The addition of several patient characteristics can increase the ability to predict VO2 max and account for more of the variability. Such information is valuable when assessing patient response to therapeutic intervention if respiratory gas analysis is unavailable or impractical.
authors.affiliation: Lung Transplant Program, Mass General Hospital, Boston 02114, USA.
authors.forename: L
authors.initials: L
authors.lastname: Cahalin
authors.forename: P
authors.initials: P
authors.lastname: Pappagianopoulos
authors.forename: S
authors.initials: S
authors.lastname: Prevost
authors.forename: J
authors.initials: J
authors.lastname: Wain
authors.forename: L
authors.initials: L
authors.lastname: Ginns
mesh_terms: D001784:Blood Gas Analysis; D005080:Exercise Test / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D016014:Linear Models; D008171:Lung Diseases / Q000175:diagnosis / Q000503:physiopathology*; D016040:Lung Transplantation / Q000502:physiology* / Q000706:statistics & numerical data; D008297:Male; D015999:Multivariate Analysis; D010101:Oxygen Consumption / Q000502:physiology*; D011379:Prognosis; D012129:Respiratory Function Tests / Q000379:methods / Q000706:statistics & numerical data; D013997:Time Factors; D016138:Walking / Q000502:physiology*