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

Abstract

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 O2 concentrations (ΔFO2). However, little is known about the response of ΔFO2 to pulmonary rehabilitation (PR). The aim of the present study was (1) to investigate whether PR increases peak V’O2, based on whether ΔFO2 or V’E at peak exercise increase after PR, and (2) to investigate whether an improvement in ΔFO2 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 ΔFO2 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 O2 extraction following PR correlated with improved exercise tolerance and ventilatory efficiency. In advanced COPD patients, a new strategy for improving O2 extraction ability might be effective in those in whom ventilatory ability can be only minimally increased.

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“…To date, the studies that have examined the utility of assessing ventilatory efficiency in the evaluation of COPD patients with dyspnea have been relatively few with small numbers of participants. 28,32,33,[37][38][39][40][41][42][43] Phillips and colleagues from the Canadian Research Group Canadian study of Chronic Obstructive Lung Disease (CanCOLD) were well positioned to address this question. The consortium of 9 respiratory research centers in Canada has assembled a cross-sectional cohort of Canadians over 40 years old who have undergone a battery of tests including pulmonary function testing, exercise tolerance testing, computed tomography (CT) scanning, modified Medical Research Council (mMRC) breathlessness and COPD assessment test scoring.…”

It’s Time to Run!

“…Previously, data demonstrated that exercise training improves peak oxygen consumption in heart failure patients by increasing the cardiac output with an unchanged average arteriovenous oxygen difference, suggesting the crucial role of blood flow distribution towards the periphery [17]. In this Special Issue, Miyazaki and colleagues [18] deeply investigated exertional pathophysiology conditions, specifically evaluating oxygen extraction measurements following rehabilitation in chronic obstructive pulmonary patients. The same intriguing comparison between pulmonary and cardiac patients' pathophysiologies was also performed by evaluating different parameters, such as minute ventilation for a given carbon dioxide production, which is known to also have a relevant prognostic power in heart failure patients [19].…”