Admission SpO₂/FiO₂ ratio for mortality risk stratification in children with severe pneumonia: a multicenter...

Severe pneumonia remains a major cause of pediatric intensive care unit (PICU) admission and death, particularly in settings where access to vaccination, timely care, and reliable oxygen systems is uneven. Conventional prognostic assessment combines clinical severity, organ dysfunction, and laboratory biomarkers, but many components are intermittent or invasive. This study aimed to evaluate whether the admission peripheral oxygen saturation to fraction of inspired oxygen (SpO₂/FiO₂; S/F) ratio provides additional, non-invasive prognostic information in children with severe pneumonia requiring respiratory support.

This multicenter retrospective cohort study included 218 children with severe pneumonia admitted to the PICUs of three teaching hospitals in China from December 2021 to November 2024. Admission clinical characteristics, respiratory support, oxygenation indices, and laboratory variables were extracted from electronic medical records. The primary outcome was in-hospital mortality. Associations with mortality were evaluated using group comparisons, correlation analysis, exploratory logistic regression, and receiver operating characteristic (ROC) analysis.

Sixty-one children died, giving an in-hospital mortality rate of 28.0%. Non-survivors had lower admission S/F and SpO₂/FiO₂ (P/F) ratios and more frequently received invasive mechanical ventilation. Higher lactate, alanine aminotransferase (ALT), and blood urea nitrogen (BUN) levels were associated with increased mortality risk. In exploratory logistic regression, a higher S/F ratio was associated with lower mortality risk [odds ratio (OR) 0.988 per one-unit increase, 95% confidence interval (CI): 0.981-0.995; P=0.001]. The S/F ratio showed modest single-marker discrimination [area under the curve (AUC), 0.637].

The admission S/F ratio was inversely associated with in-hospital mortality in children with severe pneumonia requiring respiratory support. It may be used at PICU admission and after changes in oxygen therapy as a rapid adjunct to clinical assessment, severity scores, lactate, and organ dysfunction markers. Because discrimination was modest and respiratory-support modalities were heterogeneous, the S/F ratio should not be used alone or as a fixed treatment threshold without prospective validation.