Increased Oxygen Extraction by Pulmonary Rehabilitation Improves Exercise Tolerance and Ventilatory Efficiency in Advanced Chronic Obstructive Pulmonary Disease

Background: In cardiopulmonary exercise testing (CPET), oxygen uptake (V'(O2)) is calculated using the product of minute ventilation (V'(E)) and the difference between inspiratory and expiratory O-2 concentrations (Delta FO2). However, little is known about the response of Delta FO2 to pulmonary rehabilitation (PR). The aim of the present study was (1) to investigate whether PR increases peak V'(O2), based on whether Delta FO2 or V'(E) at peak exercise increase after PR, and (2) to investigate whether an improvement in Delta FO2 correlates with an improvement in ventilatory efficiency. Methods: A total of 38 patients with severe and very severe COPD, whose PR responses were evaluated by CPET, were retrospectively analyzed. Results: After PR, peak V'(O2) was increased in 14 patients. The difference in Delta FO2 at peak exercise following PR correlated with the difference in peak V'(O2) (r = 0.4884, p = 0.0019), the difference in V'(E)/V'(CO2)-nadir (r = -0.7057, p < 0.0001), and the difference in V'(E)-V'(CO2) slope (r = -0.4578, p = 0.0039), but it did not correlate with the difference in peak V'(E). Conclusions: The increased O-2 extraction following PR correlated with improved exercise tolerance and ventilatory efficiency. In advanced COPD patients, a new strategy for improving O-2 extraction ability might be effective in those in whom ventilatory ability can be only minimally increased.

Automated summary

This study found that pulmonary rehabilitation (PR) can increase peak oxygen uptake (V' (O2)) and improve exercise tolerance and ventilatory efficiency in patients with COPD. The improvement in oxygen extraction ability correlated with the difference in peak V' (O2) and ventilatory efficiency, suggesting that a new strategy for improving oxygen extraction ability may be effective in patients with limited ventilatory ability.