This is a single-center cross-sectional study designed to compare the diaphragmatic morphofunction and respiratory drive among four groups: OSA, COPD, overlap syndrome (patients with both OSA and COPD), and healthy controls. Participants will undergo overnight polysomnography (PSG), spirometry, impulse oscillometry, and diaphragm ultrasound combined with surface EMGdi measurements. The study will analyze group differences in diaphragmatic thickness, excursion, thickening fraction, and EMGdi parameters including EMGdi-rest, EMGdi-max, and EMGdi%max. The relationships between diaphragmatic indicators and respiratory parameters (FEV1, FVC, AHI, R5-R20, etc.) will also be assessed. This study aims to provide objective evidence for diaphragmatic dysfunction characterization in OSA and COPD, as well as to explore its diagnostic utility in overlap syndrome.
