Increased Oxygen Consumption Ability With Pulmonary Rehabilitation Improves Submaximal Exercise Capacity in Advanced COPD

Abstract

Background:

Improving the anaerobic threshold (AT) provides benefits by avoiding overload, especially for patients with advanced COPD. However, the variables related to improving AT are poorly known. The aim of this study was to investigate which variables are related to improved AT after pulmonary rehabilitation (PR) using cardiopulmonary exercise testing (CPET).

Methods:

Stable patients with severe and very severe COPD who performed 4-week PR and whose ATs were identified both before and after PR were selected; they were divided into two groups based on whether the AT increased after PR, and their responses were compared.

Results:

In the 26 eligible subjects, there was no correlation between the mean change from baseline after PR in the inspired minus expired mean O₂ concentrations (ΔFO₂) and minute ventilation (V˙_E) at peak exercise. Compared with the AT no-increase group, the AT increase group, at peak exercise, showed significant increases in peak oxygen uptake (V˙_O2 ) and ΔFO₂ but not in V˙_E, after PR. The increase in V˙_O2 at the AT after PR was well correlated with the mean change after PR in ΔFO₂ at peak exercise (r = 0.66, P < .001), rather than V˙_E. Of all the peaks and throughout exercise variables, ΔFO₂ at peak exercise was identified as one of the variables more closely correlated with improved AT after PR.

Conclusions:

Improvement of ΔFO₂ at peak exercise, rather than V˙_E, correlated with an increased AT in subjects with advanced COPD, which suggests that improving ΔFO₂ independent of V˙_E may be a useful strategy to individualize PR.