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

Study objective : To assess the relationship of distance ambulated dur ing the 6-min walk test (6'WT) to maximal oxygen consumption (Vo(2) ma x). Design: Multivariate analysis of patient characteristics to Vo(2) max. Setting: Pre-lung transplant evaluation. Patients: 60 patients (2 2 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). Mea surements and results: The 6'WT was performed on a level hallway surfa ce, and Vo(2) max was obtained during maximal cycle ergometry exercise testing with respiratory gas analysis. Multivariate analysis of patie nt characteristics (age, sex, weight, FEV(1), FVC, diffusing capacity for carbon monoxide (Dco), 6'WT distance ambulated, number of rests pe r 6'WT, and the maximal heart rate, blood pressure, rate-pressure prod uct, respiratory rate, oxygen saturation, rating of perceived exertion , and amount of supplemental oxygen used during the 6'WT) was performe d on two groups of 30 patients each (group A or B) who were randomly a ssigned to either group by a process of random selection using a compu ter-generated random numbers program. Distance ambulated was the stron gest independent predictor of Vo(2) max (r=0.73; p<0.0001) in both gro ups, 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 distan ce ambulated during the 6'WT to Vo(2); max, the prediction equation ob tained from the multivariate analysis of group A, Vo(2) max=0.006xdist ance (feet) +3.38, was used to estimate the Vo(2) max of the group B p atients. 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 p atient characteristics can increase the ability to predict Vo(2) max a nd account for more of the variability. Such information is valuable w hen assessing patient response to therapeutic intervention if respirat ory gas analysis is unavailable or impractical.