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).