At th second interim analysis, the DSMB recommended discontinuation of the trial for futility. The sponsor took this recommendation into account and decided to prematurely terminate the study

The goal of this clinical trial is to determine whether one of the two oxygenation or ventilation strategies (NIV and/or HFNO) is superior to standard oxygen to reduce 28-day mortality rate in hypoxemic acute respiratory failure (ARF) patients.

This randomized controlled trial is a superiority study to test if one of the methods (NIV and/or HFNO) is superior to standard oxygen in ARF patients requiring oxygen. It is an investigator-initiated, multicenter, adaptive, three arms parallel-group trial with a computer-generated allocation sequence and an electronic system-based randomization, with a stratification on medical (then stratification between immunocompromised and non-immunocompromised patients) versus surgical (then stratification between cardiothoracic and abdominal patients).

Inclusion Criteria:

• Adult (age ≥ 18 years)
• A diagnosis of hypoxemic ARF occurring defined as the presence and persistence for more than 30 minutes of hypoxemia (defined by a partial oxygen pressure <60 mm Hg when breathing room air or <80 mmHg when breathing 15 L/min of oxygen or a peripheral oxygen saturation [SpO2] ≤90% when breathing room air and/or a PaO2(partial pressure of oxygen)/FiO2 ratio < 300 mmHg plus either [1] a respiratory rate higher than 30/min or [2] clinical signs suggestive of intense respiratory muscle work and/or labored breathing, such as use of accessory respiratory muscles, paradoxical motion of the abdomen, or intercostal retraction).

Exclusion Criteria:

• Contraindications to NIV and/or HFNO
• Sleep apnea syndrome with home ventilator
• Immediate tracheal intubation
• Requirement for an emergent surgical procedure requiring intubation
• Hypercapnia with a formal indication for NIV (formal indication for NIV with PaCO2 ≥ 50 mmHg or clinical signs of hypercapnia)
• Isolated cardiogenic pulmonary edema (formal indication for NIV). Patients with pulmonary edema associated with another ARF etiology can be included.
• Anatomical factors precluding the use of NIV and/or HFNO
• Patients with limitation or withdrawal of life-sustaining therapies with a do-not-intubate order
• Pregnancy in progress or planned during the study period or breastfeeding women
• Patients protected by law (Art. L1121-6 and L1121-8 of the Code de la Santé Publique): Adult protected by law or patient under guardianship or curatorship
• Subjects not covered by public health insurance
• Absence of written informed consent from the patient or his or her proxy (if present) before inclusion or when possible when the patient has been included in an emergency setting

Only the statisticians will have access to the full trial dataset during the enrolment period. All data will be made available to the coordinator at the end of inclusion. Controlled access will be granted to participant-level data sets.

Technical appendix, statistical code, and dataset will be available on demand.

Immediately following publication, no end date.

Data will be available for the corresponding author on reasonable request.