Age ≥ 18 years

Ventilator-dependent ARDS, with all of the following (a-e):

1. Invasive ventilation with positive end-expiratory pressure (PEEP) ≥ 8 cm H2O or FiO2 ≥ 0.5

2. Hypoxemia as characterized by: • If arterial blood gas (ABG) available: the partial pressure of oxygen in the arterial blood (PaO2)/FiO2 ≤ 300 mm Hg, or, • if ABG not available OR overt clinical deterioration in oxygenation since last ABG: SpO2/FiO2 ≤ 316 with SpO2 ≤ 97% (both conditions) on two representative assessments between 1 to 6 hours apart. • If patient is positioned prone or receiving inhaled pulmonary vasodilator at time of screening:

   Qualifying PaO2/FiO2 or SpO2/FiO2 (as defined above) that was recorded within the 6 hours immediately prior to initiating either of these therapies may be used for eligibility determination. • If PEEP has been increased by > 5 cm H2O within the last 12 hours immediately prior to screening:

   Qualifying PaO2/FiO2 or SpO2/FiO2 (as defined above) prior to PEEP increase may be used for eligibility determination if recorded within this 12-hour window.

3. Bilateral lung opacities on chest imaging not fully explained by effusions, lobar collapse, or nodules

4. Respiratory failure not fully explained by heart failure or fluid overload

5. Onset within 1 week of clinical insult or new/worsening symptoms

Early in ARDS course

• Full criteria for ARDS (#2 above) first met within previous 3 days
• Current invasive ventilation episode not more than 4 days duration
• Current severe hypoxemic episode (receipt of invasive ventilation, noninvasive ventilation, or high-flow nasal cannula) not more than 10 days duration