inclusion criteria: hospitalized patients with confirmed covid-19 infection and symptoms, with an oxygenation index defined as quotient of partial pressure of oxygen in arterial blood (pao2, in mmhg) and fraction of inspired oxygen (fio2) \> 200.

inclusion criteria: hospitalized patients with confirmed covid-19 infection and symptoms, with an oxygenation index defined as quotient of partial pressure of oxygen in arterial blood (pao2, in mmhg) and fraction of inspired oxygen (fio2) \> 200.

inclusion criteria: hospitalized patients with confirmed covid-19 infection and symptoms, with an oxygenation index defined as quotient of partial pressure of oxygen in arterial blood (pao2, in mmhg) and fraction of inspired oxygen (fio2) > 200.

inclusion criteria: hospitalized patients with confirmed covid-19 infection and symptoms, with an oxygenation index defined as quotient of partial pressure of oxygen in arterial blood (pao2, in mmhg) and fraction of inspired oxygen (fio2) > 200.