Acute respiratory distress syndrome remains a deadly disease with hospital mortality remaining between 40 to 50%. ARDS mortality risk factors have been identified from patient history, common clinical and biological variables in the lung SAFE study. Part of ARDS mortality is attributable to ventilator-induced lung injury (VILI), in relation with inappropriate settings on the ventilator. Tidal hyperinflation and recruitment/derecruitment during lung inflation are 2 identified mechanisms leading to VILI, that may be identified on computed tomography while poorly identified with variables collected at the bedside.

The aim of this study is to identify whether tidal hyperinflation identified on computed tomography is a risk factor for ARDS mortality, independently from know bio-clinical risk factors.

Inclusion Criteria:

• Patient aged 15 or older with ARDS according to the Berlin definition
• invasive mechanical ventilation with PaO2/FiO2 ≤ 300 mm Hg
• with computed tomography acquired at both end-expiration and end-inspiration, or at both PEEP 5 and 15 cm H2O at end-expiration
• PEEP setting according to a PEEP/FiO2 table, with secondary adjustment according to hemodynamic tolerance
• Tidal volume 6 ml/kg of predicted body weight or less

Exclusion Criteria:

• Use of contrast agent during computed tomography acquisition
• ARDS criteria onset since more than 72 hours or ECMO onset since more than 72 hours
• Proven COPD
• Pneumothorax or bronchopleural fistula
• Patient with spontaneous breathing preventing realization of end-expiratory and end-inspiratory pauses
• Previous inclusion in current study
• Patient under a legal protective measure

Patients will be screened from the population of patient hospitalized for ARDS in the participating centers