Evaluation of the FreeO2 System for Oxygen Weaning After Acute Hypoxemic Respiratory Failure

Inclusion Criteria: * Age ≥18 years * Acute hypoxemic respiratory failure requiring high-flow nasal oxygen therapy for at least 12 hours * Fraction of inspired oxygen (FiO₂) ≤35% * Peripheral oxygen saturation (SpO₂) ≥ the predefined lower target threshold: * 88% in patients at risk of hypercapnia * 94% in patients without risk of hypercapnia * Women of childbearing potential must use an effective contraceptive method (oral contraceptives, injectable contraceptives, intrauterine device, double-barrier method, contraceptive patch); women must be postmenopausal for at least 24 months or surgically sterilized * Patient's oral agreement and absence of written refusal to participate, indicating that the participant has understood the study objectives and required procedures and agrees to participate and comply with study-related requirements and restrictions * Affiliation with or beneficiary of the French social security system Exclusion Criteria: * Age \<18 years * Uncontrolled acute respiratory acidosis requiring invasive or non-invasive mechanical ventilation * Unstable peripheral oxygen saturation (SpO₂) * Excessive bronchial secretions * Carbon monoxide poisoning * Severe cardiocirculatory failure (mean arterial pressure \<65 mmHg without fluid resuscitation and/or requiring vasopressors, and/or severe arrhythmia) * Acute neurological failure (Glasgow Coma Scale \<15, or new-onset sensorimotor deficit) * Acute kidney injury requiring renal replacement therapy * Known untreated severe obstructive sleep apnea