inclusion criteria: * covid-19 pneumonia according to the diagnostic criteria in effect at the time of inclusion or very strongly suspected. * patient treated by nasal high flow. * moderate or severe ards: bilateral radiological opacities not explained entirely by effusions, atelectasis or nodules; acute hypoxemia with worsening within the 7 previous days, not entirely explained by left ventricular failure; pao2 / fio2 ratio \<300 mmhg (or spo2 / fio2 equivalent). * informed consent. * beneficiary or affiliated to a social security scheme.

inclusion criteria: * covid-19 pneumonia according to the diagnostic criteria in effect at the time of inclusion or very strongly suspected. * patient treated by nasal high flow. * moderate or severe ards: bilateral radiological opacities not explained entirely by effusions, atelectasis or nodules; acute hypoxemia with worsening within the 7 previous days, not entirely explained by left ventricular failure; pao2 / fio2 ratio \<300 mmhg (or spo2 / fio2 equivalent). * informed consent. * beneficiary or affiliated to a social security scheme.

inclusion criteria: - covid-19 pneumonia according to the diagnostic criteria in effect at the time of inclusion or very strongly suspected. - patient treated by nasal high flow. - moderate or severe ards: bilateral radiological opacities not explained entirely by effusions, atelectasis or nodules; acute hypoxemia with worsening within the 7 previous days, not entirely explained by left ventricular failure; pao2 / fio2 ratio <300 mmhg (or spo2 / fio2 equivalent). - informed consent. - beneficiary or affiliated to a social security scheme.

inclusion criteria: - covid-19 pneumonia according to the diagnostic criteria in effect at the time of inclusion or very strongly suspected. - patient treated by nasal high flow. - moderate or severe ards: bilateral radiological opacities not explained entirely by effusions, atelectasis or nodules; acute hypoxemia with worsening within the 7 previous days, not entirely explained by left ventricular failure; pao2 / fio2 ratio <300 mmhg (or spo2 / fio2 equivalent). - informed consent. - beneficiary or affiliated to a social security scheme.