S/F and ROX indices in predicting failure of high-flow nasal cannula in children

A high-flow nasal cannula (HFNC) is a useful respiratory support for children with respiratory distress; however, it elevates the risk of belated intubation. Recently, indices based on percutaneous oxygen saturation, a fraction of inspired oxygen, and respiratory rate (RR) have been suggested for the prediction of HFNC failure. We aimed to evaluate various indices predicting HFNC failure in children who started receiving HFNC at a tertiary center for 27 months.

Cases of HFNC failure were classified as hypoxic respiratory failure (HRF) or non-HRF (NHRF) depending on the cause of intubation. The ratio of percutaneous oxygen saturation to the fraction of inspired oxygen (S/F), the ratio of S/F to RR (ROX), the ratio of S/F to RR/median RR (ROX-M), and the ratio of S/F to z-score of RR (ROX-Z) were calculated and compared between groups.

Of the 152 cases, 45 (29.6%) failed to wean from the HFNC support, of which 21 (46.7%) were HRFs and 24 (53.3%) were NHRFs. The S/F and ROX-M at 6 h and 3 h, respectively, predicted HRF well with a high area under the curve. Initial hypercapnia and low weight were good predictors for NHRF.

For the management of children with HFNC, these risk factors and indicators should be monitored to make an early decision regarding intubation.