Functional residual capacity and elastic power as prognostic markers in acute respiratory distress syndrome

To determine if functional residual capacity (FRC) and elastic power (EP) could predict outcomes in patients with acute respiratory distress syndrome (ARDS).

This retrospective study included 353 ARDS patients admitted to our hospital between 2018 and 2025. Patients were categorized into good (n=251) and poor (n=102) prognosis groups based on their 28-day outcomes. FRC was measured using nitrogen washout, and EP was calculated using the formula: 0.098 × VT × RR × ½(PEEP + Pplat). After comparing these parameters between groups, multivariate regression and ROC analyses were performed to identify predictors. We validated our findings in an external cohort of 101 patients.

Poor outcome patients had significantly lower FRC and higher EP (both P<0.001). A positive correlation between EP and mortality was observed (rho=0.298, P<0.001), while FRC showed a significant inverse relationship (rho=-0.177, P<0.001). Multivariate analysis confirmed that EP (OR=1.251, P<0.001), FRC (OR=0.956, P=0.039), ARDS severity (OR=8.421, P<0.001), and PEEP (OR=1.338, P=0.011) were independent predictors of outcomes. A predictive model combining FRC and EP showed strong performance, with an AUC of 0.809 in internal validation and 0.819 in the external cohort. EP alone exhibited a high specificity of 0.944 at a cutoff value of 21.535 J/min.

ARDS patients with low FRC and high EP face an increased risk of mortality. Combining these measures enhances prognostic accuracy and can help tailor ventilation strategies for improved outcomes.