The body weight-walking distance product as related to lung function, anaerobic threshold and peak (V)over dot O-2 in COPD patients

The product of walking distance and body weight (D W) mimics the work of wa lking. We hypothesized the superiority of D-W to walking distance (D) alone in any correlation with lung function: anaerobic threshold(PLT) and maxima l oxygen uptake (VO2max). We further hypothesized that the D W product for a 6-min walk test (6 MWT) would correlate with the AT and VO2max because al l three are markers of exercise ability. Thirty-three male chronic obstruct ive pulmonary disease (COPD) patients with mean forced expiratory volume in 1sec (FEV1) of 1.2+0.41 (range 0.58-1.86 1) were enrolled. Six patients we re excluded due to inabiIity to achieve a maximal test. Lung function and s elf-assessed every-day activities using a oxygen-cost diagram were evaluate d before entry of the study. A maximal effort ramp-pattern cardiopulmonary exercise test (CPET) and a 6 MWT were conducted in random order. Borg score , heart rate: and O-2 Saturation with pulse oximetry (SPO2) were measured d uring both exercise tests. VO2, AT and minute ventilation were also measure d during the CPET. Correlations were sought between the distance covered in the 6 MWT, and the D W product with AT, VO2max and other variables. The av erage D and D-W were 456m and 27.5kgkm(-1), respectively. D W was superior to D alone when correlated with the VO2max and AT determined from the CPET, while modestly correlated with the change Cd) in Borg score and DeltaS(P)O (2) in the 6MWT and self-assessed every-day activities. Distance x weight p roduct was correlated with the PIT and VO2max. In addition, D W was better correlated with diffusing capacity for carbon monoxide and vital capacity t han D alone. We conclude that D W mimics the work of walking better than D and is suggested as a parameter for evaluation of patients' fitness if gas exchange measurements are not available.