Diaphragmatic Excursion is Correlated With the Improvement in Exercise Tolerance After Pulmonary Rehabilitation in Patients With Chronic Obstructive Pulmonary Disease
Abstract Background: In patients with chronic obstructive pulmonary disease (COPD), the maximum level of diaphragm excursion (DEmax) is correlated with dynamic lung hyperinflation and exercise tolerance. This study aims to clarify the utility of DEmax to predict the improvement in exercise tolerance after pulmonary rehabilitation (PR) in patients with COPD.Methods: This was a prospective cohort study. Sixty-two patients with stable COPD participated in an outpatient PR programme from April 2018 to February 2021, and 50 completed the programme. Six-minute walk distance (6MWD) was used to evaluate exercise tolerance, and ultrasonography was used to measure DEmax. Responders to PR in exercise capacity were defined as patients with an increase >30 m in 6MWD. The receiver operating characteristic (ROC) curve was used to determine the cut-off point of DEmax to predict responses to PR.Results: Baseline levels of forced expiratory volume in one second (%FEV1), 6MWD, maximum inspiratory pressure (PImax), DEmax and quadriceps muscle strength (QMS) were significantly higher, and peak dyspnoea of modified Borg (mBorg) scale was lower in responders (n = 30) than in non-responders (n = 20) to PR (p < 0.01). In multivariate analysis, DEmax was significantly correlated with an increase of >30 m in 6MWD. The area under the ROC curve of DEmax to predict responders was 0.915, with a sensitivity of 83% and a specificity of 95% at a cut-off point of 44.9 mm of DEmax.Conclusion: DEmax well predicted the improvement in exercise tolerance after PR in patients with COPD.