Characterization of the microVAScular Dysfunction in Covid-19 ARDS

The primary endpoint of this research is to establish that the alveolar dead space is significantly higher in patients with COVID-19 ARDS, compared to patients with non-COVID-19 ARDS. Secondarily, the investigators want to establish the prognostic value of the alveolar-dead space (measured iteratively) in patients with COVID-19 and non-COVID-19 ARDS, to establish the respective influences of the biological parameters of endothelial damage, of the biological parameters of coagulopathy, of the parameters set on the artificial ventilator on the value of the alveolar dead space; in ARDS patients with COVID-19 and non-COVID-19 ARDS, to establish the prognostic value of the laboratory parameters of endothelial damage and coagulopathy in patients with COVID-19 and non-COVID-19 ARDS.

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