Inclusion and exclusion criteria

According to the Extracorporeal Life Support Organization (ELSO) [10], ECMO can be initiated when risk of death exceeds 80%, where PaO₂/FiO₂ is less than 100 mm Hg on FiO₂ more than 90%, and Murray score is 3–4, or in the case of hypercapnia as indicated by PaCO₂ over 80 mm Hg or inability to achieve safe inflation pressures (plateau pressure <30 cm H₂O). Patients were excluded if they 1) had been on mechanical ventilation for more than 10 days, 2) showed contraindication to anticoagulation, 3) had irreversible multiple organ failure, 4) had severe chronic pulmonary parenchymal disease, or 5) were in the terminal stage of cancer.