THE RELATIONSHIP OF THE 6-MIN WALK TEST TO MAXIMAL OXYGEN-CONSUMPTION IN TRANSPLANT CANDIDATES WITH END-STAGE LUNG-DISEASE

Study objective : To assess the relationship of distance ambulated during the Design: Multivariate analysis of patient characteristics to Vo(2) max. Setting: Pre-lung transplant evaluation. Patients: 60 patients (22 men, 38 women; mean age, 44 years) with end-stage lung disease (mean FEV(1) and forced vital capacity of 0.97 and 1.93, respectively). Measurements and results: The 6'WT was performed on a level hallway surface, and Vo(2) max was obtained during maximal cycle ergometry exercise testing with respiratory gas analysis. Multivariate analysis of patient characteristics (age, sex, weight, FEV(1), 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 Vo(2) max (r=0.73; p<0.0001) in both groups, and adding age, weight, and pulmonary function test results (FVC, FEV(1), 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 Vo(2); max, the prediction equation obtained from the multivariate analysis of group A, Vo(2) max=0.006xdistance (feet) +3.38, was used to estimate the Vo(2) 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) Vo(2) max (mean difference, 0.5 ml/kg/min; SD of the difference=2.88). Conclusions: The distance ambulated during a 6'WT can predict Vo(2) max in patients with end-stage lung disease. The addition of several patient characteristics can increase the ability to predict Vo(2) 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.