This cross-sectional observational study aims to assess the diaphragmatic morphofunction and respiratory drive characteristics among patients with obstructive sleep apnea (OSA), chronic obstructive pulmonary disease (COPD), overlap syndrome (OS), and healthy controls. Using ultrasound imaging and surface diaphragm electromyography (EMGdi), the study will explore group differences in diaphragmatic morphology, function, and respiratory drive indicators, and evaluate their clinical significance in disease differentiation and severity assessment.
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.
Study Type
OBSERVATIONAL
Enrollment
80
Non-invasive assessment of diaphragmatic morphofunction and respiratory drive using ultrasound imaging and diaphragm electromyography (EMG). This evaluation will be performed once per participant without any therapeutic intervention.
The First Affiliated Hospital of Nanjing Medical University
Nanjing, Jiangsu, China
RECRUITINGDiaphragmatic electromyography (EMGdi-rest) at baseline
To assess resting diaphragmatic electromyographic activity (µV) across OSA, COPD, Overlap, and control groups using surface and esophageal EMG.
Time frame: Baseline (at enrollment)
Diaphragmatic EMG during maximal inspiration (EMGdi-max)
To assess maximal inspiratory diaphragmatic EMG activity (µV) using voluntary effort tests with surface and esophageal EMG.
Time frame: Baseline (at enrollment)
Relative inspiratory EMG effort (EMGdi%max)
To calculate the ratio of EMGdi-rest to EMGdi-max as a percentage, reflecting the relative inspiratory effort.
Time frame: Baseline (at enrollment)
Diaphragmatic excursion measured by ultrasound during deep breathing
To evaluate diaphragmatic mobility (cm) during deep breathing using standardized ultrasound protocols.
Time frame: Baseline (at enrollment)
Respiratory impedance parameter R5
To compare small airway resistance (kPa·s·L-¹) between groups using impulse oscillometry.
Time frame: Baseline (at enrollment)
Respiratory resistance at 20 Hz (R20)
To compare central airway resistance (kPa·s·L-¹) using impulse oscillometry.
Time frame: Baseline (at enrollment)
Difference in resistance (R5-R20)
To evaluate small airway dysfunction by calculating the difference between R5 and R20 (kPa·s·L-¹) .
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Time frame: Baseline (at enrollment)
Forced expiratory volume in 1 second (FEV1)
To compare FEV1 (L) across groups and assess its relationship with diaphragmatic function.
Time frame: Baseline (at enrollment)
Forced vital capacity (FVC)
To compare FVC (L) across groups and assess pulmonary capacity.
Time frame: Baseline (at enrollment)
FEV1/FVC ratio
To evaluate airflow obstruction using the FEV1/FVC ratio (%).
Time frame: Baseline (at enrollment)
Apnea-hypopnea index (AHI)
To evaluate sleep-disordered breathing severity (events/hour) in OSA and Overlap groups.
Time frame: Baseline (at enrollment)
Oxygen desaturation index (ODI)
To assess oxygen desaturation frequency during sleep (events/hour) using PSG data.
Time frame: Baseline (at enrollment)
Minimum oxygen saturation (SpO₂ min)
To capture the lowest oxygen saturation (%) during overnight monitoring.
Time frame: Baseline (at enrollment)
Time below 90% oxygen saturation (T90)
To calculate the percentage of sleep time with oxygen saturation \< 90% (%).
Time frame: Baseline (at enrollment)