• Pierachille Santus, Dejan Radovanovic, Giovanni Balzano, Matteo Pecchiari, Rita Raccanelli, Nicola Sarno, Fabiano Di Marco, Paul W Jones, and Mauro Carone.
• Department of Health Science, University of Milan, Pulmonary Rehabilitation Unit, Fondazione Salvatore Maugeri, IRCCS - Scientific Institute of Milan, Milan, Italy.
• Respiration. 2016 Jan 1; 92 (5): 295-307.

BackgroundLung diffusing capacity (DLCO) and lung volume distribution predict exercise performance and are altered in COPD patients. If pulmonary rehabilitation (PR) can modify DLCO parameters is unknown.ObjectivesTo investigate changes in DLCO and ventilation inhomogeneity following a PR program and their relation with functional outcomes in patients with COPD.MethodsThis was a prospective, observational, multicentric study. Patients were evaluated before and after a standardized 3-week PR program. Functional assessment included body plethysmography, DLCO, transfer factor (KCO) and alveolar volume (VA), gas exchange, the 6-min walking test (6MWT) and exercise-related dyspnea. Patients were categorized according to the severity of airflow limitation and presence of ventilation inhomogeneity, identified by a VA/TLC <0.8.ResultsTwo hundred and fifty patients completed the study. Baseline forced expiratory volume in 1 s (FEV1) % predicted (mean ± SD) was 50.5 ± 20.1 (76% males); 137 patients had a severe disease. General study population showed improvements in 6MWT (38 ± 55 m; p < 0.01), DLCO (0.12 ± 0.63 mmol × min-1 kPa-1; p < 0.01), lung function and dyspnea. Comparable improvements in DLCO were observed regardless of the severity of disease and the presence of ventilation inhomogeneity. While patients with VA/TLC <0.8 improved the DLCO increasing their VA (177 ± 69 ml; p < 0.01), patients with VA/TLC >0.8 improved their KCO (8.1 ± 2.8%; p = 0.019). The latter had also better baseline lung function and higher improvements in 6MWT (14.6 ± 6.7 vs. 9.0 ± 1.8%; p = 0.015). Lower DLCO at baseline was associated with lower improvements in 6MWT, the greatest difference being between subjects with very severe and mild DLCO impairment (2.7 ± 7.4 vs. 14 ± 2%; p = 0.049).ConclusionsIn COPD patients undergoing a PR program, different pathophysiological mechanisms may drive improvements in DLCO, while ventilation inhomogeneity may limit improvements in exercise tolerance.© 2016 S. Karger AG, Basel.

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