Correlation Between Diaphragmatic Excursion and Exercise Tolerance Improvement Following Pulmonary Rehabilitation in Patients with Chronic Obstructive Pulmonary Disease-Obstructive Sleep Apnea Overlap Syndrome

Honghua Shen,1,2 Yiming Xu,2 Yin Zhang,2 Lei Ren,2 Rui Chen1 1Department of Respiratory Medicine, the Second Affiliated Hospital of Soochow University, Suzhou, 215004, People’s Republic of China; 2Department of Respiratory Rehabilitation, the Fourth Rehabilitation Hospital of Shanghai, Shanghai, 200040, People’s Republic of ChinaCorrespondence: Rui Chen, Department of Respiratory Medicine, the Second Affiliated Hospital of Soochow University, Suzhou, 215004, People’s Republic of China, Email chenruigood@126.comPurpose: We assess the predictive value of diaphragm excursion (DE) in enhancing exercise tolerance following pulmonary rehabilitation (PR) among patients with COPD-OSA overlap syndrome.Material and Methods: This prospective cohort study enrolled 63 patients diagnosed with COPD-OSA overlap syndrome who actively participated in a PR program from January 2021 to May 2023. Among these, 58 patients successfully completed the 20-week PR program, with exercise tolerance assessed through the measurement of six-minute walk distance (6MWD), and DE evaluated by ultrasonography. The responder to PR in terms of exercise ability was defined as a patient who showed an increase of > 30m in 6MWD. The cutoff value for predicting PR response based on DE was determined using receiver operating characteristic (ROC) curves.Results: Following the PR program, significant improvements were observed in mMRC, 6MWD, DE during deep breathing, and diaphragm thickness fraction (DTF). Of the participants, 33 patients (57%) were classified as responders, while 25 patients (43%) were considered non-responders. Baseline values of FEV1% predicted, 6MWD, DE during deep breathing, DTF, and PaO2 exhibited a significant elevation in responders as compared to non-responders. The changes of 6MWD were positively associated with the baseline values of DTF and DE during deep breathing, FEV1% predicted and PaO2, while negatively correlated with baseline value of mMRC. The predictive performance in terms of the area under the ROC curve for determining responder’s DTF was found to be 0.769, accompanied by a sensitivity of 85% and specificity of 68%, using a cutoff value at 17.26%. Moreover, it was observed that DE during deep breathing could predict the area under the ROC curve for responders to be 0.753, with a sensitivity of 91% and specificity of 56% at a cutoff value of 3.61cm.Conclusion: Diaphragm excursion serves as a valuable predictor for determining the enhancement of exercise tolerance following PR in patients with COPD-OSA overlap syndrome.Trial Registration: ChiCTR1800020257, www.chictr.org.cn/index.aspx.Keywords: pulmonary rehabilitation, COPD-OSA overlap syndrome, diaphragm excursion, diaphragm thickness fraction, six-minute walk distance