Abstract
Background
COPD patients undergoing pulmonary rehabilitation (PR) show various responses. The purpose of this study was to investigate the possible mechanisms and predictors of the response to PR in COPD patients.
Methods
Thirty-six stable COPD patients underwent PR including a 4-week high-intensity exercise training program, and they were evaluated by cardiopulmonary exercise testing. All patients (mean age 69 years, severe and very severe COPD 94%) were classified into four groups by whether the exercise time (Tex) or the peak oxygen uptake
increased after PR: two factors increased (both the Tex and the peak
increased); two factors decreased; time only increased (the Tex increased, but the peak
economized); and
only increased (the Tex decreased, but the peak
increased). Within all patients, the relationships between baseline variables and the post-to-pre-change ratio of the time–slope, Tex/(peak minus resting
), were investigated.
Results
Compared with the two factors increased group (n=11), in the time only increased group (n=18), the mean differences from pre-PR at peak exercise in 1) minute ventilation
(P=0.004),
(P<0.0001), and carbon dioxide output
(P<0.0001) were lower, 2)
/
(P=0.034) and
/
(P=0.006) were higher, and 3) the dead space/tidal volume ratio (VD/VT) and the dyspnea level were similar. After PR, there was no significant difference in the ratio of the observed peak heart rate (HR) to the predicted peak HR (220 – age [years]) between the two groups. A significant negative correlation with the baseline time–slope (r=−0.496, P=0.002) and a positive correlation with the baseline body mass index (BMI) (r=0.496, P=0.002) were obtained.
Conclusions
PR in COPD patients improves Tex rather than exercise tolerance, economizing oxygen requirements, resulting in reduced ventilatory requirements without cardiac loads followed by reduced exertional dyspnea. In addition, the time–slope and BMI could be used to predict PR responses beforehand.
Acknowledgments
The authors received no specific funding for this study. The authors would like to thank Mr K Tsuguchi (CMIC-PMS Co., Ltd, Tokyo, Japan), who had no relevant conflicts of interest, for performing the statistical analysis. The authors would also like to thank Ms S Ito and Ms S Sakaguchi for their help with the CPET measurements.
Disclosure
The authors report no conflicts of interest in this work.