Diaphragm Ultrasound Distinguishes Exacerbation From Stable Status in Chronic Obstructive Pulmonary Disease

Background: The importance of evaluating the diaphragm muscle in chronic obstructive pulmonary disease (COPD) is widely accepted. However, the role of diaphragm ultrasound (DUS) in COPD is not fully understood. We set this study to evaluate the role of DUS for distinguishing the status of COPD. Methods: COPD patients who underwent DUS were enrolled between March 2020 and November 2020. The diaphragm thickening fraction (TF max ) and diaphragm excursion (DE max ) during maximal deep breathing were measured. Patients were divided into exacerbation and stable groups. Demographics, lung function, and DUS findings were compared between the two groups. Receiver operating characteristic (ROC) curve and univariate/multivariate logistic regression analyses were performed. Results: Fifty-five patients were enrolled. The exacerbation group had a lower body mass index (BMI) (20.9 vs. 24.2, p = 0.003), lower TF max (94.8 ± 8.2% vs. 158.4 ± 83.5%, p = 0.010), and lower DE max (30.8 ± 11.1 mm vs. 40.5 ± 12.5 mm, p = 0.007) compared to stable group. The areas under the TF max (0.745) and DE max (0.721) curves indicated fair results for distinguishing exacerbation. The patients were divided into low and high TF max and DE max groups based on calculated cut-off values. Low TF max (odds ratio [OR] 8.40; 95% confidence interval [CI] 1.55–45.56) and low DE max (OR 11.51; 95% CI 1.15–115.56) were associated with exacerbation after adjusting for age, sex, BMI, forced vital capacity and forced expiratory volume in 1 sec. Conclusion: TF max and DE max distinguished exacerbation from stable status. We describe the DUS cut-off values for determining an exacerbation status in this study.