Association between respiratory rate oxygenation index and need for positive pressure ventilation in children on high flow nasal cannula for bronchiolitis.

Our objective was to evaluate the association of respiratory rate oxygenation index (ROX) with the need for positive pressure ventilation in children < 2 years of age with bronchiolitis on high flow nasal cannula (HFNC) therapy. We performed a single-center prospective observational study of a convenience sample of children < 2 years of age with bronchiolitis who had HFNC initiated in the pediatric emergency department between November and March, 2018-2020. ROX was calculated as pulse oximetry/FiO2/respiratory rate at HFNC initiation. Demographics, need for positive pressure ventilation (PPV), disposition, and hospital length of stay were collected. Logistic regression model was used to determine the odds ratio for PPV need relative to the highest ROX quartile. Of the 373 patients included, 49 (13.1%) required PPV. ROX was lower in patients who required PPV compared with those who did not (5.86 [4.71-7.42] vs. 6.74 [5.46-8.25]; p = 0.01). Logistic regression revealed that those patients whose ROX was in the lowest quartile (< 5.39) were three times more likely to require PPV compared to those in the highest quartile (> 8.21). These results held true after adjusting for confounders (odds ratio 3.1; 95% CI [1.3 to 7.5]; p = 0.02). The model's AUROC (0.701) indicated acceptable discrimination between cases and controls. CONCLUSION: Low ROX index was associated with the need for PPV in children with bronchiolitis on HFNC. The risk stratification provided and ROX threshold for risk stratification require confirmation in other populations with a larger sample size. WHAT IS KNOWN: • Demographic and clinical factors associated with high flow nasal cannula (HFNC) therapy in children with bronchiolitis has been studied. WHAT IS NEW: • This is the first study to  report the utility of association of Respiratory Rate Oxygenation (ROX) index for need for positive pressure ventilation (PPV) in children < 2 years of age with bronchiolitis on HFNC therapy. • ROX was lower in children who required PPV and children whose ROX was in the lowest quartile (< 5.39) were three times more likely to require PPV compared to those in the highest quartile (> 8.21).