Method:
This is an ancillary study to the multicenter randomized controlled trial TRAMONTANE 2, that included 286 infants of less than 6 months with moderate-to-severe AVB. Collection of physiological variables at baseline (H0), and 1 hour after HFNC (H1), included heart rate (HR), respiratory rate (RR), fraction of inspired oxygen (FiO2), respiratory distress score (mWCAS), and pain and discomfort scale (EDIN). ROX was calculated as SpO2/FiO2 to RR. Predefined HFNC failure criteria included increase in respiratory distress score or respiratory rate, increase in discomfort, and severe apnea episodes. The accuracy of ROX index to predict HFNC failure was assessed using receiver operating curve analysis.