The role of baseline PaO2/FiO2, SpO2 and IL-6 indicators in predicting in-hospital mortality in ARDS patients: a retrospective cohort study

Abstract

Objective
The aim of this study was to evaluate the role of baseline oxygenation parameters, including PaO2/FiO2 and SpO2, as well as the inflammatory marker IL-6, in predicting in-hospital mortality among patients treated in the intensive care unit with a diagnosis of acute respiratory distress syndrome (ARDS).

Methods
This retrospective cohort study included 97 patients diagnosed with ARDS who were treated in the intensive care unit and had available baseline PaO2/FiO2, SpO2, and IL-6 measurements. Patients were divided into two groups according to clinical outcome: survivors and non-survivors. Baseline oxygenation and inflammatory parameters were compared between the groups. Factors associated with in-hospital mortality were evaluated using logistic regression analysis. The prognostic performance of individual parameters and the combined model was assessed using receiver operating characteristic (ROC) analysis.

Results
Among the 97 patients included in the study, 58 survived and 39 died during hospitalization, resulting in an overall in-hospital mortality rate of 40.2%. Non-survivors had significantly lower PaO2/FiO2 and SpO2 values compared with survivors, while IL-6 levels were significantly higher. In ROC analysis, PaO2/FiO2 showed the highest prognostic performance among individual parameters, with an area under the curve (AUC) of 0.944. The AUC values were 0.911 for SpO2 and 0.868 for IL-6. The combined model including PaO2/FiO2, SpO2, and IL-6 demonstrated the highest discrimination ability, with an AUC of 0.962.

Conclusion
Low baseline PaO2/FiO2 and SpO2 levels and elevated IL-6 values are strongly associated with in-hospital mortality in patients with ARDS. The combined use of oxygenation parameters and IL-6 may provide a simple, accessible, and clinically useful approach for early mortality risk stratification in intensive care settings.