Changes in six-minute walking distance during pulmonary rehabilitation in patients with COPD and in healthy subjects

Background: The six-minute walking distance (6MWD) test has demonstrated validity and reliability to assess changes in functional capacity following pulmonary rehabilitation in patients with chronic obstructive lung disease. However, no attempt has been made to establish an iterative measurement of 6MWD during the overall period of pulmonary rehabilitation. Therefore, the aim of this study was to evaluate the impact of a twelve-week rehabilitation program on the iterative weekly measurement of 6MWD in chronic obstructive pulmonary disease (COPD) patients and healthy subjects.

Methods: Twenty-six patients with COPD and nine age-matched healthy subjects were studied. Measurements were taken at baseline and after twelve weeks except for the 6MWD. The exercise measurements included a six-minute walking test (6MWT) and an incremental exercise test. Oxygen saturation, heart rate, and dyspnea will be monitored during all these tests.

Results: At baseline there were significant differences between groups, except in age, body mass index, and oxygen saturation. After 12 weeks, there was no significant change in lung function in patients with COPD and healthy subjects. The 6MWD, peak oxygen uptake (.)VO(2peak) and anaerobic threshold increased significantly after training in both groups (P < 0.01). The averaged trace of the 6MWD of patients with COPD and healthy subjects was followed-up respectively by a logarithmic and linear fitting. 6MWD showed a plateau after eight weeks in patients with COPD, however, it increased continually overall in healthy subjects.

Conclusion: Both patients with COPD and healthy subjects demonstrated functional responses to training but with somewhat different patterns in quality of the improvement of the 6MWD.