Despite the use of protective ventilation, neuromuscular blocking agent and prone position, ARDS mortality remains high (30%-50%) in observational studies, and pneumothorax rate in randomized controlled trial remains stable (10%). The driving pressure (the ratio of tidal volume over respiratory system compliance) has recently been strongly associated with ARDS mortality, suggesting that tidal volume reduction below 6ml/kg may offer mortality benefit. While extracorporeal CO2 removal technique are currently under investigation in association with tidal volume reduction

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