Inclusion Criteria:  Patient above 18 year-old. Diagnosis of severe ARDS due to COVID-19 under invasive mechanical ventilation, Meet criteria for PP: PaO2/FiO2 < 150 millimeters of mercury column (mmHg), PEEP ≥ 5 Centimeters of Water (cmH2O), FiO2 ≥ 60.  Exclusion Criteria:  No consent for the study. PP contraindicated (( elevated intracranial pressure, massive hemoptysis, recent tracheal surgery or sternotomy, unstable hemodynamic status, recent pacemaker implantation, severe facial laceration, open abdominal wound, spine, femur or pelvis fracture or pregnancy).