Diaphragm Ultrasound is an Imaging Biomarker that Distinguishes Exacerbation Status from Stable Chronic Obstructive Pulmonary Disease

Background: Evaluating the diaphragm muscle in chronic obstructive pulmonary disease (COPD) is important. However, the role of diaphragm ultrasound (DUS) in distinguishing the exacerbation status of COPD (AECOPD) is not fully understood. We set this study to evaluate the role of DUS as a biomarker for distinguishing the AECOPD. 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 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 AECOPD. 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 AECOPD after adjusting for age, sex, BMI, and lung functions. Conclusion: DUS showed the possibility of an imaging biomarker distinguishing AECOPD from stable status.