Pulmonary rehabilitation for COPD improves exercise time rather than exercise tolerance: effects and mechanisms.

Miki K, Maekura R, Kitada S, Miki M, Yoshimura K, Yamamoto H,
Kawabe T, Kagawa H, Oshitani Y, Satomi A, Nishida K, Sawa N,
Inoue K

Int J Chron Obstruct Pulmon Dis. 2017 Apr 3;12:1061-1070

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 [Formula: see text] increased after PR: two
factors increased (both the Tex and the peak [Formula: see text] increased); two
factors decreased; time only increased (the Tex increased, but the peak [Formula:
see text] economized); and [Formula: see text] only increased (the Tex decreased,
but the peak [Formula: see text] increased). Within all patients, the
relationships between baseline variables and the post-to-pre-change ratio of the
time-slope, Tex/(peak minus resting [Formula: see text]), 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 [Formula: see text] (P=0.004), [Formula: see text] (P<0.0001),
and carbon dioxide output [Formula: see text] (P<0.0001) were lower, 2) [Formula:
see text]/ [Formula: see text] (P=0.034) and [Formula: see text]/ [Formula: see
text] (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.