Signs of respiratory failure despite noninvasive ventilation or a high-flow nasal cannula
| Patients on noninvasive ventilation |
| Tidal volume > 9.5 mL/kg ideal body weight consistently over the first 4 hours |
| Fraction of inspired oxygen (FiO2) > 60% to maintain target oxygen saturation (SpO2) |
| Patients on high-flow nasal cannula |
| ROX index (ratio of SpO2/FiO2/respiratory rate) ≥ 4.88 at 2, 6, and 12 hours is a good predictor of no need for intubation, and < 3.85 predicts high risk of need for intubation |