The key problem in the treatment of ARDS is refractory hypoxemia. Extracorporeal Membrane Oxygenation (ECMO) is an extracorporeal oxygenation of venous blood to eliminate carbon dioxide and return to the body. It has been an important part of the rescue treatment for ARDS. This study intends to explore the timing of ECMO. The main research hypothesis is that the appropriate timing of ECMO treatment can improve the weaning success rate and survival rate of children with severe ARDS; it is expected to provide a basis for determining the best timing of ECMO treatment

Severe acute respiratory distress syndrome (ARDS), especially those caused by severe viral pneumonia, is still an important factor in the death of children, with a case fatality rate of 55%. The treatment includes lung protective ventilation and advanced ventilation support, but the effect is still not ideal for severe patients. ECMO can effectively support the respiratory system and provide good oxygen exchange. However, the survival rate of ECMO treatment in children with ARDS has a large bias.One of the key factors is the uneven timing of ECMO activation, which significantly affects the prognosis.This study intends to design a multi-center, prospective, non-randomized controlled trial , through retrospective research to find relevant factors affecting the prognosis of ECMO treatment, and to screen key indicators related to the timing of intervention; through a prospective cohort study to screen Good indicators and cut-off values suitable for starting ECMO , constructing and verifying comprehensive prediction models.

Inclusion Criteria:

• Acute onset; within 7 days of clinical insult
• Chest imaging (radiograph or computed tomography) findings of new infiltrates (unilateral or bilateral) consistent with acute parenchymal disease
• Edema not fully explained by fluid overload or cardiac failure
• May present as new acute lung disease in setting of chronic lung disease and/or heart disease
• OI≥16
• Viral etiology is clear

Exclusion Criteria:

• Perinatal lung disease
• Large intracranial bleed with mass effect or need for neurosurgical intervention
• Hypoxic cardiac arrest without adequate CPR
• Irreversible underlying cardiac or lung pathology (and not a transplant candidate)
• Pulmonary hypertension and chronic lung disease
• Chronic multiorgan dysfunction
• Incurable malignancy
• Allogenic bone marrow recipients with pulmonary infiltrates
• Hepatic or renal failure
• Pertussis infection in infants
• Fungal pneumonia
• Immunodeficiency

children with acute respiratory distress syndrome（ARDS） admitted to the pediatric intensive care unit（PICU） of all the study centers