Diaphragmatic Thickening Fraction and Excursion: Different Clinical Values in Non-Critically Ill Patients with AECOPD — An Exploratory Study

Purpose: Diaphragm dysfunction is a key mechanism of respiratory failure during acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Diaphragmatic thickening fraction (DTF) and excursion (DE) are commonly used ultrasound parameters, but their clinical value in non-critically ill AECOPD patients remains unclear. This study aimed to investigate the association of early DTF and DE with subsequent noninvasive ventilation (NIV) requirement and treatment response. Patients and Methods: This retrospective observational study enrolled AECOPD patients admitted between December 2025 and January 2026. DTF and DE were measured within 24 hours of admission and before NIV initiation. Primary outcomes were NIV requirement within 48 hours, and among NIV recipients, the difference in ultrasound parameters between treatment responders and non-responders. Multivariable logistic regression assessed whether DTF provided incremental information beyond traditional clinical predictors. Results: Of 123 included patients, 56 received NIV. DTF was significantly higher in the NIV group than in the non-NIV group ( P =0.033), while DE did not differ. After adjusting for traditional clinical indicators, DTF was no longer significant ( P =0.121). Among NIV-treated patients, DE was significantly higher in responders than in non-responders ( P =0.015), while DTF did not differ. Conclusion: In non-critically ill AECOPD patients, elevated DTF is associated with NIV requirement but does not provide independent predictive information beyond traditional clinical indicators. DE is associated with NIV treatment response and may reflect diaphragmatic contractile reserve. These exploratory findings, including subgroup analyses and threshold estimates, require prospective validation before clinical application. The two parameters have distinct clinical values, and their interpretation should consider disease stage.