Oxygen Saturation Index as a Predictor of Surfactant Requirement in Neonates with Respiratory Distress Syndrome: A Prospective Observational Study

Objectives The study aimed to evaluate the predictive value of the oxygen saturation index (OSI) for surfactant requirement in neonates with respiratory distress syndrome (RDS) and to determine optimal cutoff values for guiding surfactant therapy. Material and Methods This prospective observational study was conducted at the neonatal intensive care unit (NICU) of a tertiary care teaching hospital in Gujarat, India, over 18 months (IEC Approval No: SVIEC/ON/Medi/BNPG/22/DEC/23/II2). A total of 104 neonates with RDS requiring respiratory support within 6 h of birth were enrolled. Surfactant (beractant 100 mg/kg) was administered based on clinical deterioration, radiological evidence of RDS, and FiO₂ requirement, following European Consensus Guidelines on RDS management (2022 update). OSI was calculated using the formula: [mean airway pressure (cmH₂O) × FiO₂ (%)]/SpO₂ (%). For neonates on nasal continuous positive airway pressure (nCPAP), mean airway pressure was estimated as set CPAP pressure plus a correction factor. Measurements were recorded at admission (0 h) and at 2, 4, and 6 h. Receiver operating characteristic (ROC) curve analysis determined optimal cutoff values. Statistical analysis was performed using SPSS version 26.0. Results Of 104 neonates, 42 (40.4%) required surfactant therapy. Of the total cohort, 84 (80.8%) were initially placed on nCPAP and 20 (19.2%) on mechanical ventilation; 22 (21.2%) required escalation from nCPAP to mechanical ventilation. The median time to surfactant administration was 3.2 h (IQR: 2.1–4.8). The surfactant group had significantly higher mean OSI at admission (3.58 ± 0.89 vs. 2.04 ± 0.62, p <0.001). ROC analysis revealed an optimal OSI cutoff of 2.6 at admission with 85.7% sensitivity, 77.4% specificity, and an AUC of 0.913 (95% CI: 0.857–0.969). A critical OSI cutoff of 2.2 provided 95.2% sensitivity with 56.5% specificity. Multivariate analysis identified gestational age <30 weeks (OR 7.85, 95% CI: 2.89–21.32), OSI ≥2.6 (OR 6.78, 95% CI: 2.45–18.76), and FiO₂ ≥0.4 (OR 5.13, 95% CI: 1.98–13.29) as independent predictors. On separate multivariate logistic regression analysis for mortality, OSI >3.5 at admission (OR 22.74, 95% CI: 4.12–125.63, p <0.001) and gestational age <28 weeks (OR 14.12, 95% CI: 2.56–77.89, p = 0.002) were significant independent predictors of mortality. Conclusion OSI at admission is a reliable, non-invasive predictor of surfactant requirement in neonates with RDS. An OSI cutoff of 2.6 provides optimal predictive accuracy, while 2.2 serves as a critical threshold for high-sensitivity screening. OSI >3.5 is an independent predictor of mortality on multivariate regression analysis. Serial OSI monitoring can guide timely surfactant administration, particularly in settings where arterial blood gas analysis is unavailable.