Inclusion Criteria:  All patients (age 18 and older) will be eligible for inclusion if they meet all of the following consensus criteria for sepsis and ARDS.  Patients with sepsis are defined as those with life-threatening organ dysfunction caused by a dysregulated host response to infection:  Suspected or proven infection: Sites of infection include thorax, urinary tract, abdomen, skin, sinuses, central venous catheters, and central nervous system Increase in Sequential Organ Failure Assessment (SOFA) Score ≥ 2 over baseline  ARDS is defined when all four of the following criteria are met:  A PaO2/FiO2 ratio ≤ 300 with at least 5 cm H2O positive end-expiratory airway pressure (PEEP) 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 A need for positive pressure ventilation by an endotracheal or tracheal tube 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 is present  Exclusion Criteria:  An individual who meets any of the following criteria will be excluded from participation in this study:  Age less than 18 years Greater than 168 hours since ARDS onset Pregnant or breastfeeding Prisoner 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) No consent/inability to obtain consent or appropriate legal representative not available Physician refusal to allow enrollment in the trial Moribund patient not expected to survive 24 hours No arterial line or central line/no intent to place an arterial or central line No intent/unwillingness to follow lung protective ventilation strategy Severe hypoxemia defined as SpO2 < 95 or PaO2 < 90 on FiO2 ≥ 0.9 Hemoglobin < 7.0 g/dL Subjects who are Jehovah's Witnesses or are otherwise unable or unwilling to receive blood transfusions during hospitalization Acute myocardial infarction (MI) or acute coronary syndrome (ACS) within the last 90 days Coronary artery bypass graft (CABG) surgery within 30 days Angina pectoris or use of nitrates with activities of daily living Severe cardiopulmonary disease classified as New York Heart Association (NYHA) class IV 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 Burns > 40% total body surface area Severe airway inhalational injury Use of high frequency oscillatory ventilation Use of extracorporeal membrane oxygenation (ECMO) Use of inhaled pulmonary vasodilator therapy (eg. nitric oxide [NO] or prostaglandins) Diffuse alveolar hemorrhage from vasculitis Concurrent participation in other investigational drug study