Background: Impaired exercise capacity is one of the most important prognostic factors for patients with chronic obstructive pulmonary disease (COPD). The 6-min walk test (6MWT) is a widely used method for assessing exercise capacity in patients with COPD. However, the 6MWT requires considerable effort from patients. Therefore, a less physically demanding, but also noninvasive, method is warranted. The objective of this study was to determine the predictors of the 6MWT distance (6MWD) in patients with COPD.
Methods: This retrospective observational study enrolled 133 Japanese patients with COPD. All patients underwent the 6MWT, COPD assessment test (CAT), spirometry, respiratory muscle strength evaluation, body composition assessment, and handgrip strength (HGS) measurement. We examined the associations between the 6MWD and evaluated parameters.
Results: From single regression analysis, the 6MWD was significantly correlated with age, CAT score, several spirometric measurements (e.g., percentages of forced vital capacity, forced expiratory volume in 1 s, and carbon monoxide diffusing capacity of the lungs [%DLCO]), respiratory muscle strength parameters (e.g., percentages of maximal expiratory and inspiratory pressures), skeletal muscle mass index, and HGS. In multiple regression analysis, age, CAT score, %DLCO, and HGS were independent predictors of the 6MWD. The %DLCO and HGS were strongly correlated as predictors of the 6MWD (p < 0.001).
Conclusions: We found that HGS was significantly correlated with the 6MWD compared with spirometric measurements or respiratory muscle strength parameters in Japanese patients with COPD, suggesting that HGS could be a simple and noninvasive predictor of the 6MWD in patients with COPD.
Keywords: 6-min walk test distance; Chronic obstructive Pulmonary disease; Exercise capacity; Handgrip strength; Pulmonary function testing.
Copyright © 2019 The Japanese Respiratory Society. Published by Elsevier B.V. All rights reserved.