Inclusion Criteria:  Age> 18 years old Invasive mechanical ventilation in place for less than 48 hours Severe or moderate ARDS (defined according to the Berlin classification) Virological confirmation by PCR of SARS-CoV-2 infection (ARDS COVID-19) Lack of virological confirmation by PCR of SARS-CoV-2 infection (ARDS not linked to COVID-19) Patient information  Exclusion Criteria:  Massive pulmonary embolism Chronic respiratory failure under long-term oxygen therapy Dying patient