Fig. 2

ROX index performance to predict HFNO failure at different times after HFNO initiation HFNO: high-flow nasal oxygen therapy; red line gives proportion of patients in the HFNO failure group with a ROX index ≤ a chosen cut-off value; black line gives proportion of patients in the HFNO success group with a ROX index ≤ a chosen cut-off value. For example: at H12, using a Rox index of ≤ 9.75 as cut-off would identify 90% of patients with HFNO failure after H12, whereas this cut-off would identify only 41% of patients with HFNO success after H12, avoiding intubation