The aim of this observationnal study is to describe respiratory mechanics and lung recruitement in patients with SARS-CoV-2 Associated Acute Respiratory Distress Syndrome who underwent invasive ventilation on endotracheal tube, admitted to the medical ICU of Angers university hospital . Statics measurements of respiratory system compliance were performed at 2 differents levels of PEEP (15 cmH2O and 5 cmH2O). The recruited volume is computed as the difference between the volume expired from PEEP 15 to 5 cmH2O and the volume predicted by compliance at PEEP 5 cmH2O . The recruitment-to-Inflation (R/I) ratio (i.e. the ratio between the recruited lung compliance and CRS at PEEP 5 cmH2O) is used to assess lung recruitability. A R/I ratio value higher than or equal to 0.5 was used to define highly recruiter patients.

The investigators perform an observational prospective study in patients admitted to medical ICU in Angers University hospital with a confirmed COVID 19 pneumonia and who require invasive ventilation on endotracheal tube. Participants receive initially deep sedation and neuromuscular blockers for 24 hours and are ventilated in volume-controlled mode with a tidal volume of 6 mL/kg of predicted body weight, a constant inspiratory flow of 60 L/minute and a respiratory rate adjusted to maintain pH above 7.35 when possible. A PEEP decremental trial from 15 to 5 cmH2O was performed (15 minutes by step).

Esophageal pressure monitoring and electrical impedance tomography (EIT) are collected if available. Arterial blood gases and respiratory mechanics are measured at the end of each step.

The recruitment-to-Inflation (R/I) ratio (i.e. the ratio between the recruited lung compliance and CRS at PEEP 5 cmH2O) is used to assess lung recruitability. A R/I ratio value higher than or equal to 0.5 is used to define highly recruiter patients.

By the end of the recording time, a low-flow (5 L/min) inflation from PEEP 5 cmH2O (tidal volume = 6ml/kg PBW) is then performed after a prolonged expiration to identify a potential airway closure and the corresponding airway opening pressure (AOP).

Investigators perform these measurements at day 1, day 5 and day 10 from ICU admission if participants still require controlled ventilation.

The investigators also collect clinical data about each participant (past medical history, ICU discharge, hospital discharge, date of death, ventilator acquired pneumonia, thromboembolic event, use of NO, use of ECMO or renal replacement therapy).

Inclusion Criteria:

• ARDS criteria according to Berlin classification criteria
• Invasive mechanical ventilation on endotracheal tube
• SARS Cov-2 infection

Exclusion Criteria:

• pneumothorax

Mechanically Ventilated adult patients with COVID-19 Associated ARDS