Closed Loop Oxygen Control in INtubated Critically Ill Patients

Inclusion Criteria: * Patients admitted to the ICU who are expected to require invasive mechanical ventilation for at least 8 hours and are expected to stay respiratory stable´ in the upcoming 8 hours. * Acute respiratory failure with PaO2/FiO2 \<300 with FiO2 ≥ 0.4 at inclusion * Age older than 18 years old. * Written informed consent signed and dated by the patient or one relative in case that the patient is unable to consent, after full explanation of the study by the investigator and prior to study participation. Exclusion Criteria: * Low quality on the SpO2 measurement using finger and ear sensor (quality index \<60%). * Hemodynamic instability defined as a need of continuous infusion of epinephrine or norepinephrine \> 1 mg/h. * Severe acidosis (pH ≤ 7.30). * Chronic or acute dyshemoglobinemia: methemoglobin, CO poisoning, sickle cell disease. * Patient under guardianship or deprived of liberties. * Impossibility to give informed consent by both patient and family (i.e. language barrier). * Patient included in another interventional research study under consent with similar outcome.