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 (ΔFO ₂ ). However, little is known about the response of ΔFO ₂ to pulmonary rehabilitation (PR). The aim of the present study was (1) to investigate whether PR increases peak V' _O2 , based on whether ΔFO ₂ or V' _E at peak exercise increase after PR, and (2) to investigate whether an improvement in ΔFO ₂ 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 ΔFO ₂ 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.