Prognostic assessment of the COPD patient: it is time to consider respiratory muscle ultrasound

BACKGROUND: Diaphragm and intercostal muscle dysfunction is common in patients with chronic obstructive pulmonary disease (COPD) due to high airway resistance and generalized skeletal muscle atrophy. Ultrasound is a noninvasive test that provides real-time assessment of respiratory muscle movement and function. METHODS: This single-center, prospective study was conducted at the respiratory medicine and ultrasound departments of a tertiary hospital over a period of 17 months, from January 2024 to June 2025. The research evaluated diaphragmatic and intercostal muscle thickness, thickening fraction, shear wave elastography parameters, and diaphragmatic mobility in COPD patients. Participants were stratified into high-risk and low-risk groups based on the clinical Body-Mass Index, airflow Obstruction, Dyspnea, and Exercise Capacity Index (BODE) for subsequent data analysis. A repeatability assessment was conducted on 50 healthy controls prior to the study to establish the reliability of the ultrasound parameters for respiratory muscle evaluation. RESULTS: Between January 2024 and June 2025, ninety-six COPD patients with 50 healthy subjects were included, and the inter-observer reproducibility for diaphragm thickness of end-inspiratory (DTei), diaphragm thickness of end-expiratory (DTee), diaphragm thickening fraction (DTF), diaphragm excursion (DE), diaphragm shear wave velocity (D-SWV), diaphragm young’s elastic modulus (D-E), intercostal muscle thickness (ICMT), intercostal muscle thickening fraction (ICMTF), intercostal shear wave velocity (ICM-SWV) and intercostal young’s elastic modulus (ICM-E) were 0.948, 0.953, 0.893, 0.877, 0.857, 0.897, 0.969, 0.851, 0.903, and 0.912, respectively. Among the two-dimensional parameters, DTei (P = 0.004), DTF (P = 0.003), DE (P = 0.002), and ICMTF (P = 0.021) were independent influences in diagnosing a population at high risk for BODE, the AUC was 0.939 Among the shear wave elasticity parameters, mean SWV of the intercostal muscles (P = 0.021) was an independent influencing factor, and shear wave elasticity combined with two-dimensional parameters diagnosed an AUC of 0.960. CONCLUSIONS: Respiratory muscle ultrasound demonstrates good capability in distinguishing between low-risk and high-risk BODE scores in patients with COPD. Whilst it cannot replace pulmonary function testing, respiratory muscle ultrasound serves as an effective tool for assessing future risk in COPD patients, thereby providing additional information for clinical evaluation.