Early Initiation of High-flow Nasal Cannula Oxygen Therapy in Patients With Acute Respiratory Failure in the Emergency Department: A Before-after Study

Prospective observational before-after study at the ED in two French centers. Selection of patients with acute hypoxemic respiratory failure at the ED. Application of oxygen strategy according to the period: * before period: standard oxygen delivered through nasal cannula, face mask or non-rebreathing reservoir mask, with a flow rate adjusted to maintain a pulse oxymetry of at least 92%. * after period: high-flow oxygen therapy continuously applied via large-bore nasal prongs with a gas flow rate of 50 L/min and a FiO2 adjusted to maintain a pulse oxymetry at least 92%.