To be eligible, a patient must satisfy all these inclusion criteria: 1. - Confirmed or suspected COVID-19 If ‘suspected’, results must be pending or testing intended 2. Age 18 years or older 3. Endotracheal tube in place 4. Intubated yesterday or today 5. PaO2 to FIO2 ratio less than or equal to 300 while intubated 6. Acute opacities on chest imaging affecting at least one lung quadrant 7. ‘Acute opacities’ do not include effusions, lobar/lung collapse or nodules 8. Currently in the ICU or scheduled for transfer to the ICU The ‘ICU’ is an area designated for inpatient care of the critically ill where therapies including invasive mechanical ventilation can be provided.

To be eligible, a patient must satisfy all these inclusion criteria: 1. - Confirmed or suspected COVID-19 If ‘suspected’, results must be pending or testing intended 2. Age 18 years or older 3. Endotracheal tube in place 4. Intubated yesterday or today 5. PaO2 to FIO2 ratio less than or equal to 300 while intubated 6. Acute opacities on chest imaging affecting at least one lung quadrant 7. ‘Acute opacities’ do not include effusions, lobar/lung collapse or nodules 8. Currently in the ICU or scheduled for transfer to the ICU The ‘ICU’ is an area designated for inpatient care of the critically ill where therapies including invasive mechanical ventilation can be provided.

To be eligible, a patient must satisfy all these inclusion criteria: 1. Confirmed or suspected COVID-19. Note, if ‘suspected’, results must be pending or testing intended 2. Ability to obtain informed consent/assent to participate in study 3. Age 18 years or older 4. Requiring high flow nasal oxygen or positive pressure ventilator support or invasive mechanical ventilation for a time period of no greater than 48 hours 5. D-dimers > 200 ng/ml 6. PaO2 to FIO2 ratio less than or equal to 300 7. Acute opacities on chest imaging affecting at least one lung quadrant. Note ‘Acute opacities’ do not include effusions, lobar/lung collapse or nodules 8. Currently in a higher level of care area designated for inpatient care of patients where therapies including non-positive pressure ventilatory support can be provided.

To be eligible, a patient must satisfy all these inclusion criteria: 1. Confirmed or suspected COVID-19. Note, if ‘suspected’, results must be pending or testing intended 2. Ability to obtain informed consent/assent to participate in study 3. Age 18 years or older 4. Requiring high flow nasal oxygen or positive pressure ventilator support or invasive mechanical ventilation for a time period of no greater than 48 hours 5. D-dimers > 200 ng/ml 6. PaO2 to FIO2 ratio less than or equal to 300 7. Acute opacities on chest imaging affecting at least one lung quadrant. Note ‘Acute opacities’ do not include effusions, lobar/lung collapse or nodules 8. Currently in a higher level of care area designated for inpatient care of patients where therapies including non-positive pressure ventilatory support can be provided.

To be eligible, a patient must satisfy all these inclusion criteria: 1. - Confirmed or suspected COVID-19 If ‘suspected’, results must be pending or testing intended 2. Age 18 years or older 3. Endotracheal tube in place 4. Intubated yesterday or today 5. PaO2 to FIO2 ratio less than or equal to 300 while intubated 6. Acute opacities on chest imaging affecting at least one lung quadrant 7. ‘Acute opacities’ do not include effusions, lobar/lung collapse or nodules 8. Currently in the ICU or scheduled for transfer to the ICU The ‘ICU’ is an area designated for inpatient care of the critically ill where therapies including invasive mechanical ventilation can be provided.

To be eligible, a patient must satisfy all these inclusion criteria: 1. - Confirmed or suspected COVID-19 If ‘suspected’, results must be pending or testing intended 2. Age 18 years or older 3. Endotracheal tube in place 4. Intubated yesterday or today 5. PaO2 to FIO2 ratio less than or equal to 300 while intubated 6. Acute opacities on chest imaging affecting at least one lung quadrant 7. ‘Acute opacities’ do not include effusions, lobar/lung collapse or nodules 8. Currently in the ICU or scheduled for transfer to the ICU The ‘ICU’ is an area designated for inpatient care of the critically ill where therapies including invasive mechanical ventilation can be provided.