A Clinical Study of Mesenchymal Stem Cell Exosomes Nebulizer for the Treatment of ARDS

Inclusion Criteria: 1. The subjects themselves or their family members voluntarily participate in this study and sign the informed consent form; 2. 18-70 years old, male or female; 3. Definitely diagnosed as acute respiratory distress syndrome (ARDS) (according to the Berlin definition and diagnostic criteria of ARDS); 4. Course of disease \<96 hours after diagnosis; 5. Chest X-ray showed bilateral infiltration with pulmonary edema; no clinical manifestations of left ventricular hypertension, or pulmonary artery wedge pressure (PAOP) ≤18mmHg. Exclusion Criteria: 1. Patients with severe allergic constitution; 2. Moderate to severe liver failure (children Pugh score \> 12); 3. Patients with severe chronic respiratory diseases, PaCO2 \> 50mmhg, and need home oxygen therapy; 4. Severe trauma occurred within 14 days before screening; 5. History of malignant tumor (patients with skin basal cell carcinoma in the past can be included); 6. They are undergoing hemodialysis or peritoneal dialysis; 7. The patients who had deep venous thrombosis or pulmonary embolism within 90 days; 8. Acute myocardial infarction occurred within 30 days; 9. Neuromuscular diseases that result in impaired natural ventilation include, but are not limited to, C5 or higher spinal cord injury, amyotrophic lateral sclerosis, Guillain Barre syndrome, and myasthenia gravis; 10. Obesity (BMI \> 28); 11. Lung transplantation; 12. Bone marrow transplantation; 13. Active immunosuppression is defined as receiving immunosuppressive drugs or having a medical condition associated with immunodeficiency. These included: 1) HIV (AIDS or CD4 \< 200 cells / mm3); 2) chemotherapy within 6 weeks before randomization; 3) immunosuppressive therapy, including maintenance glucocorticoid therapy (\> 40) Results: 1) short term systemic steroid therapy (intravenous or oral) for less than 1 week, topical steroid for skin diseases; 4) absolute neutrophil count \< 500 / mm3; 14. Patients undergoing extracorporeal circulation support (ECMO) or high frequency oscillatory ventilation; 15. They were not willing to receive lung protective ventilation (minimum tidal volume 6ml / kg pbw) or liquid management treatment; 16. Have a history of epilepsy, need continuous anticonvulsant therapy, or have received anticonvulsant therapy in the past 3 years; 17. The estimated survival time was less than 30 days; 18. Hepatitis B, hepatitis C, AIDS, syphilis patients; 19. Women of childbearing age are pregnant, lactating or pregnant within one year; 20. Those who could not understand the study protocol; 21. According to the judgment of the researchers, there were other situations in which the patients were not suitable to participate in the study (for example, there were factors to reduce the follow-up compliance, and the patients did not receive relevant supportive treatment, etc.).