Admission Respiratory Rate-Oxygenation Index and Outcome of Acute Respiratory Illness in a Pediatric Intensive Care Unit

Background Acute respiratory illness (ARI) remains a leading cause of pediatric intensive care unit (PICU) admissions and mortality in low- and middle-income countries. Early identification of children at risk of deterioration or ventilatory support is essential to improve outcomes. The Respiratory Rate-Oxygenation (ROX) Index, defined as (peripheral oxygen saturation (SpO₂)/fraction of inspired oxygen (FiO₂))/respiratory rate, is a non-invasive bedside tool validated in adults with respiratory failure; however, pediatric evidence is scarce. Objectives To evaluate the association of admission ROX Index with (1) mortality and (2) the requirement for positive-pressure ventilation (PPV) among children with ARI admitted to the PICU. Methods A prospective observational study was conducted among 200 consecutively admitted children aged two months to five years with ARI at a tertiary-care hospital. Demographic, anthropometric, and physiological parameters were recorded at admission. The ROX index was computed as (SpO₂/FiO₂)/respiratory rate. Primary outcomes were in-hospital mortality and need for PPV. Data were analyzed using non-parametric tests and receiver operating characteristic (ROC) analysis; p<0.05 was considered significant (STATA v14; StataCorp LLC, College Station, TX, US). Results The median age was seven months (IQR 4-12); 131 (65.5%) were male patients, and severe undernutrition (weight-for-age Z-score <−3 SD) was observed in 36 (18%) children. Overall mortality was 7% (14/200). The median admission ROX index was lower among non-survivors (5.6 (5.2-6.4)) than survivors (6.3 (5.9-7.1); p=0.002). The ROX index showed moderate discrimination for mortality (AUC=0.746; 95% CI 0.62-0.87) with an optimal cut-off ≤6.4 (sensitivity 100%, specificity 46%). For predicting PPV requirement, discrimination was good (AUC = 0.867; 95 % CI 0.80-0.93) with a cut-off ≤6.2 (sensitivity 88%, specificity 82%). Lower ROX values correlated with higher FiO₂ needs, greater tachypnea, and longer PICU stay (median eight days (IQR 6-11)). Conclusion The admission ROX index is a simple, non-invasive, and reliable predictor of mortality and ventilatory support requirement in children with acute respiratory illness. A cut-off ≤6.2 showed good discriminative accuracy for identifying high-risk cases. Its integration into triage protocols can strengthen early recognition and management of severe pediatric ARI in resource-limited PICUs.