inclusion criteria: * age ≥ 18 years old, * hospitalization for covid-19 infection confirmed by rt-pcr or other virological method, * peripheral saturation by pulse oximeter spo2 ≤ 94% in ambient air measured twice at 5-15 min intervals, or pao2 / fio2 \<300 mmhg, * abnormalities on the chest x-ray or ct scan suggestive of viral pneumonia, * signed informed consent by the patient.

inclusion criteria: * age ≥ 18 years old, * hospitalization for covid-19 infection confirmed by rt-pcr or other virological method, * peripheral saturation by pulse oximeter spo2 ≤ 94% in ambient air measured twice at 5-15 min intervals, or pao2 / fio2 \<300 mmhg, * abnormalities on the chest x-ray or ct scan suggestive of viral pneumonia, * signed informed consent by the patient.

inclusion criteria: - age ≥ 18 years old, - hospitalization for covid-19 infection confirmed by rt-pcr or other virological method, - peripheral saturation by pulse oximeter spo2 ≤ 94% in ambient air measured twice at 5-15 min intervals, or pao2 / fio2 <300 mmhg, - abnormalities on the chest x-ray or ct scan suggestive of viral pneumonia, - signed informed consent by the patient.

inclusion criteria: - age ≥ 18 years old, - hospitalization for covid-19 infection confirmed by rt-pcr or other virological method, - peripheral saturation by pulse oximeter spo2 ≤ 94% in ambient air measured twice at 5-15 min intervals, or pao2 / fio2 <300 mmhg, - abnormalities on the chest x-ray or ct scan suggestive of viral pneumonia, - signed informed consent by the patient.