Effects of Face Mask Continuous Positive Airway Pressure Vs. Noninvasive Ventilation Vs. High-flow Nasal Oxygen on Intubation-free Survival in Acute Hypoxemic Respiratory Failure: the TRIPOD Randomized Clinical Trial

Inclusion Criteria: 1. Age≥18 yrs; 2. A ratio of the partial pressure of arterial oxygen (PaO2) to the FiO2 of 300 mm Hg or less, or a ratio of pulse oximetry oxygen saturation (SpO2) to the FiO2 of 315 or less (SpO2≤97%) and the need for (1) noninvasive positive pressure ventilation with at least 5 cm H2O PEEP, or (2) high-flow nasal cannula at 30L/min or higher, or (3) standard oxygen with oxygen flow rate of at least 10 L/min; 3. Sign informed consent. Exclusion Criteria: 1. Patients that have already received Continuous positive airway pressure, Noninvasive ventilation continuously for more than 24 hours before the screening visit. 2. Previous bout of mechanical ventilation during index hospitalization. 3. Exacerbation of chronic lung disease, including asthma or chronic obstructive pulmonary disease. 4. Moderate to severe cardiac insufficiency (New York Heart Association class \>II or left ventricular ejection fraction\<50%) or cardiogenic pulmonary edema. 5. Hemodynamic dysfunction, defined as vasopressor dose \> 0.3 µg/kg/min of norepinephrine-equivalent to maintain systolic blood pressure \> 90 mm Hg. 6. Impaired consciousness with a Glasgow coma score ≤ 12. 7. Patients with urgent need for intubation, including respiratory or cardiac arrest, respiratory pauses with loss of consciousness or gasping for air, severe hypoxemia defined as SpO2 lower than 90% despite maximal oxygen support. 8. Patients with contraindication to NIV according to the French consensus conference, patient refusal, cardiorespiratory arrest, coma, non-drained pneumothorax, unresolved vomiting, upper airway obstruction, hematemesis or severe facial trauma, thoracic or abdominal surgery in the previous 7 days. 9. A do-not-intubate order at time of inclusion. 10. Pregnancy.