Improvements in Lung Diffusion Capacity following Pulmonary Rehabilitation in COPD with and without Ventilation Inhomogeneity

Abstract

Background: Lung diffusing capacity (D<smlcap>LCO</smlcap>) and lung volume distribution predict exercise performance and are altered in COPD patients. If pulmonary rehabilitation (PR) can modify D<smlcap>LCO</smlcap> parameters is unknown. Objectives: To investigate changes in D<smlcap>LCO</smlcap> and ventilation inhomogeneity following a PR program and their relation with functional outcomes in patients with COPD. Methods: This was a prospective, observational, multicentric study. Patients were evaluated before and after a standardized 3-week PR program. Functional assessment included body plethysmography, D<smlcap>LCO</smlcap>, transfer factor (KCO) and alveolar volume (V<smlcap>A</smlcap>), 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 V<smlcap>A</smlcap>/TLC <0.8. Results: Two 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), D<smlcap>LCO</smlcap> (0.12 ± 0.63 mmol × min^-1 kPa^-1; p < 0.01), lung function and dyspnea. Comparable improvements in D<smlcap>LCO</smlcap> were observed regardless of the severity of disease and the presence of ventilation inhomogeneity. While patients with V<smlcap>A</smlcap>/TLC <0.8 improved the D<smlcap>LCO</smlcap> increasing their V<smlcap>A</smlcap> (177 ± 69 ml; p < 0.01), patients with V<smlcap>A</smlcap>/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 D<smlcap>LCO</smlcap> at baseline was associated with lower improvements in 6MWT, the greatest difference being between subjects with very severe and mild D<smlcap>LCO</smlcap> impairment (2.7 ± 7.4 vs. 14 ± 2%; p = 0.049). Conclusions: In COPD patients undergoing a PR program, different pathophysiological mechanisms may drive improvements in D<smlcap>LCO</smlcap>, while ventilation inhomogeneity may limit improvements in exercise tolerance.

ACTIVATE: the effect of aclidinium/formoterol on hyperinflation, exercise capacity, and physical activity in patients with COPD

“… 32 Thus the combination of bronchodilation with non-pharmacological interventions, such as behavior modification programs to increase physical activity or pulmonary rehabilitation, may represent an important therapeutic approach to modifying pathophysiological characteristics and improving long-term outcomes in COPD. 2 , 10 , 13 , 36 …”

A comprehensive approach to lung function in bronchiectasis

“…For every patient, the VA measurements were normalized with plethysmographic TLC as suggested by Hughes et al [29]. The presence of ventilation inhomogeneity was considered as a VA/TLC <0.8 according to Santus et al [30] and Neder et al [31]. All bronchodilators and/or inhaled corticosteroids (ICS) were withdrawn 24 hours before the lung function testing.…”

Inhaled therapies in patients with moderate COPD in clinical practice: current thinking

“…71 , 72 Importantly, some of these benefits may be achieved by improvements in accessible alveolar lung volume, whereas patients with severe diffusion-capacity impairment and presence of ventilation inhomogeneity appear to experience smaller improvements in exercise tolerance. 73 By the addition of a long-acting anticholinergic bronchodilator to PR, clinically meaningful improvements in dyspnea and health status have been seen over PR alone. 74 Studies on the effect of dual bronchodilation in association with PR in patients with COPD are still lacking.…”