Ultrasonography as a way of evaluating the diaphragm muscle in patients with chronic obstructive pulmonary disease

Abstract

The respiratory muscles in chronic obstructive pulmonary disease (COPD) patients have reduced strength and resistance, leading to loss of the functional ability of these muscles. Lung hyperinflation is one of the main alterations, and air trapping is the main factor limiting diaphragmatic mobility (DM) in these patients; however, its correlation with functional parameters, exercise capacity, and indicators of disease severity remains underexplored. This study aimed to assess DM in stable COPD patients and relate the findings with parameters such as the 6-minute walk test distance, forced expiratory volume in 1 second (FEV1)%predicted, residual volume (RV)%predicted, and dyspnea. An observational cohort study was conducted to measure DM using ultrasound both at rest (DMrest) and during deep inspiration (DMmax). Forty-nine patients with stable COPD were included in this study. There was a correlation between DMmax and FEV1%predicted (R = 0.36; P = .012), RV%predicted (r = -0.42; P = .01), RV/total lung capacity (r = -0.61; P < .001), and distance reached in the 6MWT (R = 0.46; P = .001). Patients with a modified Medical Research Council score <2 exhibited greater DM than those with a score ≥2 (mean difference = 13.20 ± 4.6 mm; P = .0059). Similarly, patients with a Body Mass Index, Airflow Obstruction, Dyspnea and Exercise Capacity index ≤4 showed greater DM (61.95 mm) than those with a Body Mass Index, Airflow Obstruction, Dyspnea and Exercise Capacity index >4 (47.89 mm; mean difference = 14.05 ± 5.3 mm; 95% confidence interval = 25.09-3.01 mm). DM is correlated with bronchial obstruction (FEV1), lung hyperinflation (RV and RV/total lung capacity), exercise capacity, and dyspnea in patients with COPD, suggesting its utility as an evaluative tool in this population.