L. Cahalin et al., THE RELATIONSHIP OF THE 6-MIN WALK TEST TO MAXIMAL OXYGEN-CONSUMPTIONIN TRANSPLANT CANDIDATES WITH END-STAGE LUNG-DISEASE, Chest, 108(2), 1995, pp. 452-459
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.