inclusion criteria * adult patient (age ≥ 18 years old); * hospitalized in intensive care ; * severe covid-19 pneumonia (positive diagnosis by rt-pcr or sars-cov-2 antigen test on nasopharyngeal or deep respiratory specimen and/or evocative thoracic scan: frosted glass opacities, consolidation, cross-linking, thickening of interlobular septa, peripheral nodules) with ards criteria according to berlin criteria (pao2/fio2 ≤ 300 and pep ≥ 5). * with respiratory assistance (intubated or niv or onhd) for less than 8 days; * with an expected duration of respiratory assistance \> 48 hours; * carrier of an arterial catheter ; * for which 4 pao2/fio2 values on arterial blood over the last 24 hours are available;

inclusion criteria * adult patient (age ≥ 18 years old); * hospitalized in intensive care ; * severe covid-19 pneumonia (positive diagnosis by rt-pcr or sars-cov-2 antigen test on nasopharyngeal or deep respiratory specimen and/or evocative thoracic scan: frosted glass opacities, consolidation, cross-linking, thickening of interlobular septa, peripheral nodules) with ards criteria according to berlin criteria (pao2/fio2 ≤ 300 and pep ≥ 5). * with respiratory assistance (intubated or niv or onhd) for less than 8 days; * with an expected duration of respiratory assistance \> 48 hours; * carrier of an arterial catheter ; * for which 4 pao2/fio2 values on arterial blood over the last 24 hours are available;

inclusion criteria - adult patient (age ≥ 18 years old); - hospitalized in intensive care ; - severe covid-19 pneumonia (positive diagnosis by rt-pcr or sars-cov-2 antigen test on nasopharyngeal or deep respiratory specimen and/or evocative thoracic scan: frosted glass opacities, consolidation, cross-linking, thickening of interlobular septa, peripheral nodules) with ards criteria according to berlin criteria (pao2/fio2 ≤ 300 and pep ≥ 5). - with respiratory assistance (intubated or niv or onhd) for less than 8 days; - with an expected duration of respiratory assistance > 48 hours; - carrier of an arterial catheter ; - for which 4 pao2/fio2 values on arterial blood over the last 24 hours are available;

inclusion criteria - adult patient (age ≥ 18 years old); - hospitalized in intensive care ; - severe covid-19 pneumonia (positive diagnosis by rt-pcr or sars-cov-2 antigen test on nasopharyngeal or deep respiratory specimen and/or evocative thoracic scan: frosted glass opacities, consolidation, cross-linking, thickening of interlobular septa, peripheral nodules) with ards criteria according to berlin criteria (pao2/fio2 ≤ 300 and pep ≥ 5). - with respiratory assistance (intubated or niv or onhd) for less than 8 days; - with an expected duration of respiratory assistance > 48 hours; - carrier of an arterial catheter ; - for which 4 pao2/fio2 values on arterial blood over the last 24 hours are available;

inclusion criteria: - adult patient (age ≥ 18 years old); - hospitalized in intensive care unit (icu); - with severe covid-19 pneumonia and ards according to berlin criteria (pao2/fio2<300 and peep>5 cmh2o); - intubated for less than 8 days; - with an anticipated duration of mechanical ventilation > 48 hours; - carrier of an arterial catheter;

inclusion criteria: - adult patient (age ≥ 18 years old); - hospitalized in intensive care unit (icu); - with severe covid-19 pneumonia and ards according to berlin criteria (pao2/fio2<300 and peep>5 cmh2o); - intubated for less than 8 days; - with an anticipated duration of mechanical ventilation > 48 hours; - carrier of an arterial catheter;