Ultra Protective Ventilation Without Extracorporeal Circulation in Severe ARDS Patients (VT4ARDS)

Inclusion Criteria: * invasive mechanical ventilation * ARDS (Berlin definition) with PaO2/FiO2 ratio ≤ 150 mm Hg Exclusion Criteria: * Age below 18 year * planned duration of invasive mechanical ventilation \< 48 hours * ARDS criteria present for more than 24 hours * known or suspected intracranial hypertension * known or suspected COPD * chronic respiratory failure under long term oxygen or non-invasive ventilation * pneumothorax or broncho-pleural fistula * morbid obesity with body weight \>1 kg/cm height * sickle cell disease * recent bone marrow transplantation, aplasia following chemotherapy * burn injury on more than 30% of body surface * severe hepatic cirrhosis (Child-Pugh score C) * extracorporeal circulation life support * pregnancy * advance directives to withhold or withdraw life-sustaining treatment * previous inclusion in present study * patient under an exclusion period following inclusion in another biomedical study * patient deprived of freedom, minor, subject under a legal protective measure * lack of affiliation to social security as required by French regulation * lack of written informed consent by patient or next of kin