Safety and Efficacy Study of Inhaled Carbon Monoxide to Treat Acute Respiratory Distress Syndrome (ARDS)

Inclusion Criteria: All intubated patients ≥ 18 years old with ARDS 1. ARDS is defined when all four of the following criteria are met: 1. A PaO2/FiO2 ratio ≤ 300 with at least 5 cm H2O positive end-expiratory airway pressure (PEEP) 2. Bilateral opacities on frontal chest radiograph (not fully explained by effusions, lobar/lung collapse, or nodules) within 1 week of a known clinical insult or new or worsening respiratory symptoms 3. A need for positive pressure ventilation by an endotracheal or tracheal tube 4. Respiratory failure not fully explained by cardiac failure or fluid overload; need objective assessment (e.g., echocardiography) to exclude hydrostatic edema if no risk factor present. 2. ARDS onset is defined as the time the last of criteria 1-4 are met. ARDS must persist through the enrollment time window of 168 hours. Exclusion Criteria: An individual who meets any of the following criteria will be excluded from participation in this study: 1. Age less than 18 years 2. Greater than 168 hours since ARDS onset 3. Pregnant or breastfeeding 4. Prisoner 5. Patient, surrogate, or physician not committed to full support (exception: a patient will not be excluded if he/she would receive all supportive care except for attempts at resuscitation from cardiac arrest) 6. No consent/inability to obtain consent or appropriate legal representative not available 7. Physician refusal to allow enrollment in the trial 8. Moribund patient not expected to survive 24 hours 9. No arterial or central line/no intent to place an arterial or central line 10. No intent/unwillingness to follow lung protective ventilation strategy 11. Severe hypoxemia defined as SpO2 \< 95 or PaO2 \< 90 on FiO2 ≥ 0.9 12. Hemoglobin \< 7.0 g/dL 13. Subjects who are Jehovah's Witnesses or are otherwise unable or unwilling to receive blood transfusions during hospitalization 14. Acute myocardial infarction (MI) or acute coronary syndrome (ACS) within the last 90 days 15. Coronary artery bypass graft (CABG) surgery within 30 days 16. Angina pectoris or use of nitrates with activities of daily living 17. Cardiopulmonary disease classified as NYHA class IV 18. Stroke (ischemic or hemorrhagic) within the prior 1 month, cardiac arrest requiring CPR within the prior 72 hours, or inability to assess mental status following cardiac arrest 19. Burns \> 40% total body surface area (TBSA) 20. Severe airway inhalational injury 21. Use of high frequency oscillatory ventilation 22. Use of extracorporeal membrane oxygenation (ECMO) 23. Concomitant use of inhaled pulmonary vasodilator therapy (eg. nitric oxide \[NO\] or prostaglandins) 24. Diffuse alveolar hemorrhage from vasculitis 25. Concurrent participation in other investigational drug study