RecruitingDiagnostic testROX Index for the Timing of Intubation in Nasal High FlowLate or delayed intubation in patients with acute hypoxemic respiratory failure (AHRF) treated with nasal high flow (NHF) is associated with increased patient mortality. The ROX index has been designed and validated to predict outcome of NFH therapy by identifying those patients with a high risk of NHF failure and those with a high probability of success. Whether or not the ROX index may improve patient outcome remains to be shown. To do so, a strategy using the ROX index must lead to earlier intubation than commonly-used criteria. The objective of the ROX-1 trial is to assess whether the use of an algorithm incorporating the ROX index to standard of care for the time to intubation in patients with AHRF supported with NHF isassociated with an increase in the proportion of patients who are intubated within the first 12 hours among those patients who fail on NHF.