Pulmonary rehabilitation for COPD improves exercise time rather than exercise tolerance: effects and mechanisms
Received 24 December 2016
Accepted for publication 9 March 2017
Published 3 April 2017 Volume 2017:12 Pages 1061—1070
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Dr Colin Mak
Peer reviewer comments 2
Editor who approved publication: Dr Richard Russell
Keisuke Miki,1 Ryoji Maekura,1 Seigo Kitada,1 Mari Miki,1 Kenji Yoshimura,1 Hiroshi Yamamoto,2 Toshiko Kawabe,2 Hiroyuki Kagawa,1 Yohei Oshitani,1 Akitoshi Satomi,1 Kohei Nishida,1 Nobuhiko Sawa,1 Kimiko Inoue2
1Department of Respiratory Medicine, 2Department of Rehabilitation Medicine, National Hospital Organization, Toneyama National Hospital, Toyonaka, Japan
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 (VO2) increased after PR: two factors increased (both the Tex and the peak VO2 increased); two factors decreased; time only increased (the Tex increased, but the peak VO2 economized); and VO2 only increased (the Tex decreased, but the peak VO2 increased). Within all patients, the relationships between baseline variables and the post-to-pre-change ratio of the time–slope, Tex/(peak minus resting VO2), 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 (VE) (P=0.004), VO2 (P<0.0001), and carbon dioxide output (VCO2) (P<0.0001) were lower, 2) VE/VO2 (P=0.034) and VE/VCO2 (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.
Keywords: cardiopulmonary exercise testing, oxygen requirement, ventilatory equivalents, body weight, carbon dioxide output
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