1. Male or female, 18 years of age or older 2. Respiratory failure with the following signs and symptoms: P/F ratio <300 mmHg Onset within one week of insult or new or worsening respiratory symptoms. Chest imaging shows bilateral opacities, which are not fully explained by effusions, lobar/lung collapse, or nodules. 3. Respiratory failure which is not fully explained by cardiac failure or fluid overload. 4. Onset of respiratory failure (as defined in inclusion criterion 2) within the past 48 hours.

1. Male or female, 18 years of age or older 2. Respiratory failure with the following signs and symptoms: P/F ratio <300 mmHg Onset within one week of insult or new or worsening respiratory symptoms. Chest imaging shows bilateral opacities, which are not fully explained by effusions, lobar/lung collapse, or nodules. 3. Respiratory failure which is not fully explained by cardiac failure or fluid overload. 4. Onset of respiratory failure (as defined in inclusion criterion 2) within the past 48 hours.

1. Male or female, 18 years of age or older 2. ICU admission due to strongly suspected or proven COVID-19 3. P/F ratio <300 mmHG within the past 24 hours, but not sustained for more than 24 hours at the time of enrolment

1. Male or female, 18 years of age or older 2. ICU admission due to strongly suspected or proven COVID-19 3. P/F ratio <300 mmHG within the past 24 hours, but not sustained for more than 24 hours at the time of enrolment

1. Male or female, 18 years of age or older 2. ICU admission due to strongly suspected or proven COVID-19 3. P/F ratio <300 mmHG for less than 24 hours

1. Male or female, 18 years of age or older 2. ICU admission due to strongly suspected or proven COVID-19 3. P/F ratio <300 mmHG for less than 24 hours