Serial changes in oxygenation indices and arterial blood gas parameters during high flow nasal cannula therapy in children with moderate to severe respiratory distress: a prospective observational study

Background: Aims and objectives were to evaluate the impact of high-flow nasal cannula (HFNC) therapy on ABG parameters, oxygenation indices, and clinical outcomes in children with moderate to severe respiratory distress admitted to the PICU. Methods: This prospective observational study was conducted over 10 months at a tertiary care center. A total of 133 children aged 1 month to 14 years with respiratory distress were included. Severity was assessed using the Pediatric respiratory severity score (PRESS). Clinical and laboratory parameters were recorded at baseline, 1 hour, 12 hours, and 24 hours after initiation of HFNC therapy. Oxygenation indices, including A-a gradient, respiratory index, P/F ratio, S/F ratio, ROX index, and modified ROX index, were analyzed. Statistical analysis was performed using SPSS version 25.0. Results: Of the 133 children, 90.23% had severe respiratory distress. Significant improvements were observed in heart rate, respiratory rate, and SpO₂ over time (p<0.05). ABG analysis showed significant reductions in pCO₂ and lactate, along with improvements in pO₂, HCO₃, and base excess (p<0.05). Both ABG-dependent and independent oxygenation indices improved significantly within 24 hours (p<0.0001). HFNC failure and need for mechanical ventilation were low (1.5% each). Median ICU and hospital stay were 4 and 6 days, respectively, with 100% survival. Conclusions: HFNC therapy is a safe and effective non-invasive respiratory support modality in children with moderate to severe respiratory distress. It significantly improves oxygenation, ABG parameters, and clinical outcomes, while reducing the need for invasive ventilation.