Thoracic ratio and diaphragmatic excursion predict lung function impairment in COPD patients.

Area of Science:

• Pulmonary Medicine
• Diagnostic Imaging
• Respiratory Physiology

Background:

• Chronic obstructive pulmonary disease (COPD) significantly impacts lung function and diaphragmatic activity.
• Thoracic skeletal morphology, assessed by the TTD/ATD ratio, may influence respiratory mechanics in COPD.
• Diaphragmatic excursion during deep breathing (DE-DB) reflects respiratory muscle function and can be impaired in COPD.

Purpose of the Study:

• To examine the correlation between the TTD/ATD ratio and DE-DB in COPD patients.
• To evaluate the predictive value of these parameters for lung function impairment.
• To elucidate the underlying mechanisms and clinical utility of combined assessment using mediation and decision curve analysis.

Main Methods:

• A cross-sectional study involving 120 COPD patients.
• Measurement of TTD/ATD ratio, ultrasonographic DE-DB, and pulmonary function tests (including FEV1/FVC and FEV1% predicted).
• Statistical analyses included correlation, regression, mediation analysis, and decision curve analysis (DCA).

Main Results:

• Both TTD/ATD ratio and DE-DB decreased with increasing COPD severity and were positively correlated with each other (r=0.569, P<0.001).
• Both parameters strongly correlated with FEV1/FVC and FEV1% predicted (r=0.73-0.81, P<0.001).
• DE-DB partially mediated the effect of TTD/ATD on FEV1% predicted (26.2%). The combined model (TTD/ATD + DE-DB) showed superior predictive performance (AUC=0.963) and clinical utility via DCA, enabling effective risk stratification.

Conclusions:

• Thoracic configuration and diaphragmatic function are closely associated and independent predictors of lung function in COPD.
• Diaphragmatic function plays a partial mediating role in how thoracic configuration affects lung function.
• Combined assessment of TTD/ATD and DE-DB offers a powerful, non-invasive tool for early COPD risk stratification and personalized management.