Inclusion Criteria:

1. ARDS, defined as the acute onset of:

   • PaO2/FiO2 ≤ 200.
   • Bilateral infiltrates. The infiltrates may be patchy, diffuse, homogeneous, or asymmetric, and should be consistent with pulmonary edema or the fibrotic changes of fibroproliferation. Opacities due to pleural effusions or atelectasis should not be considered. If pneumonectomy, unilateral infiltrate is included.
   • No evidence of left atrial hypertension. If measured, PAWP ≤ 18 mmHg.
   • Criteria a-c must occur together within a 24-hour interval. The first date that these criteria are met is defined as the onset of ARDS
2. Since ARDS onset, chest infiltrates must be progressive, and chest computed tomographic scan findings are consistent with postoperative ARDS findings or ground glass opacities by radiologists.

3. Major thoracic surgery

   • Lung cancer; pneumonectomy, extended pneumonectomy, lobectomy, sleeve lobectomy, extended lobectomy, wedge resection.
   • Esophageal cancer; Ivor-Lewis operation, transhiatal esophagectomy, McKeown operation.
   • Metastatic lung cancer; simultaneous bilateral metastasectomy.
4. PaO2/FiO2 ≤ 200 on the day of E-START enrollment.

Exclusion Criteria:

1. Clinical evidence of active and untreated infection.

   Clarifications:

   • A known, undrained abscess (e.g. Staphylococcal lung abscess or loculated empyema or intra-abdominal abscess) or a known intravascular nidus of infection (e.g., bacterial or fungal endocarditis) will be a basis for exclusion, even if it is being treated with antibiotics.
   • A bacterial infection being treated with a standard antibiotic regimen would not be a basis for exclusion.
   • Disseminated fungal infection, even if being treated, is an exclusion.
   • Ongoing septic shock, even if on antibiotics is a basis for exclusion.
2. Age <18 years.
3. Pregnancy.
4. Burns requiring skin grafting.
5. Patients with AIDS by CDC criteria, diagnosed by either a documented AIDS defining illness or CD4<200(see Appendix F); prednisolone therapy >=300mg(or its equivalent) cumulative dose within 21 days prior to enrollment, or >15mg/day(or its equivalent) within 7 days prior to enrollment; cytotoxic therapy within 3 weeks.
6. Other irreversible chronic disease or condition for which 6 month mortality is estimated ≥ 50%.
7. Not committed to full support.
8. Severe chronic liver disease (Child-Pugh Class C score>10 points).
9. Transplant patients with the exception of autologous bone marrow transplants.
10. Extracorporeal support of gas exchange at the time of study entry (e.g., ECMO).
11. Known or suspected adrenal insufficiency.
12. Vasculitis with diffuse alveolar hemorrhage.