CT–measured diaphragmatic crus cross-sectional area and its association with short-term outcomes in acute exacerbations of COPD

Risk stratification for acute exacerbations of chronic obstructive pulmonary disease (AECOPD) in the emergency department (ED) is challenging. Conventional scoring systems, such as the Ottawa COPD Risk Scale (OCRS) and the Dyspnea, Eosinopenia, Consolidation, Acidemia, and Atrial Fibrillation (DECAF) score, have shown variable discrimination across populations and outcome definitions. This study investigates whether the cross-sectional area (CSA) of the diaphragmatic crus, measured by computed tomography (CT), is associated with short-term outcomes in patients with AECOPD. We conducted a retrospective analysis of 170 patients with AECOPD who presented to a tertiary ED between January 2021 and June 2024. Patients were excluded if they were under 18 years of age, had impaired consciousness, paradoxical breathing, were on long-term oxygen therapy, had atrial fibrillation, lung malignancy, were transferred to another hospital from the ED, or died within 24 h of admission. Unfavorable outcomes were defined as readmission or hospitalization within 14 days, intensive care unit (ICU) admission, prolonged hospitalization (greater than 14 days), or 30-day mortality. We performed univariable and multivariable logistic regression analyses and receiver operating characteristic (ROC) analyses. Unfavorable outcomes occurred in 60 patients (35.3%). Univariable analysis identified several predictors, including body mass index (BMI), heart rate, PCO₂, lactate, HCO₃⁻, base excess, creatinine, eosinophil count, white blood cell (WBC) count, and diaphragmatic crus CSA. Multivariable analysis indicated that crus CSA (odds ratio [OR] 7.61, 95% confidence interval [CI] 2.88–20.11, p < 0.001), eosinophil count (OR 3.86, 95% CI 1.54–9.70, p = 0.004), and WBC count (OR 0.36, 95% CI 0.14–0.94, p = 0.038) were independent predictors of unfavorable outcomes. Crus CSA, with a cutoff of 1.46 cm², achieved an area under the curve (AUC) of 0.787, numerically higher than that of OCRS (0.526) and DECAF (0.549) in this cohort; however, this comparison should be interpreted with caution, as our CT-imaged, admitted population differs from the broader populations in which OCRS and DECAF were originally developed and validated. The CT-measured CSA of the diaphragmatic crus was independently associated with adverse short-term outcomes among CT-imaged patients with AECOPD and showed numerically higher discrimination than established scoring systems within this selected cohort. It may offer a rapid and objective adjunct for risk assessment in the ED, but external validation in independent, unselected populations is required before clinical implementation.