According to the ARDS Berlin definition, patients with severe concurrent invasive mechanical ventilation were selected, and clinical data and prognosis were collected. Samples such as blood and balf were collected for analysis based on changes in the condition.

Inclusion Criteria:

1. Patients who meet the Berlin definition of ARDS and require invasive mechanical ventilation. ARDS diagnostic criteria: according to the Berlin definition, Chest radiograph shows patchy shadows in the lungs; Respiratory failure cannot be completely caused by heart failure or excessive fluid infusion
2. ARDS onset ≤ 3 days when included in the study
3. Patient PaO2/FiO2 ≤ 200mmHg when included in the study

Exclusion Criteria:

• 1) Patients with intracranial hypertension, pleural fistula, pneumothorax, HIV, HBV, HCV

  2) Age>85 years old or<18 years old

  3) Pregnant patients

  4) Severe hemodynamic instability (vasopressor increase>30% in the first 6 hours, or Norepinephrine>0.5 mg kg/min)

  5) Patients unable to perform EIT ventilation and/or perfusion testing (unable to perform internal jugular vein catheterization, Hypernatremia, chest malformation, active implant device, unstable spinal injury or fracture, skin lesions opposite the EIT monitoring area)

  6) Patients with abnormal esophageal anatomical structure and inability to indwelling gastric tubes

  7) Disagreement for inclusion in this study

According to the ARDS Berlin definition, patients with severe concurrent invasive mechanical ventilation were selected, and clinical data and prognosis were collected. Samples such as blood and balf were collected for analysis based on changes in the condition.