Effect of Nava on Weaning Outcome in Patients With Mechanical Ventilation

Inclusion Criteria: 1. Tracheotomy and invasive mechanical ventilation is expected to be required for \> 48h; 2. When support pressure ≤ 15 cmH2O, it can withstand pressure support ventilation (PSV) time \> 1h; Exclusion Criteria: 1. Age \< 18 years or \> 85 years; 2. Deep sedation. 3. Severe hemodynamic instability (norepinephrine or equivalent converted dose of other vasoactive drugs \> 1ug / kg.min or map ≤ 65mmhg) 4. Severe respiratory center depression, high paraplegia, neuromuscular disease; 5. Esophageal obstruction, esophageal perforation, severe esophageal variceal bleeding, upper gastrointestinal surgery, diaphragmatic hernia and thoracic deformity; 6. Patients with chronic respiratory diseases requiring long-term home oxygen therapy; 7. Patients with severe coagulation dysfunction (INR \> 1.5, APTT \> 44s, history of leukemia); 8. Severe other organ dysfunction is expected to die in a short time (7 days) or palliative treatment. 9. The estimated survival time of advanced solid organ or hematological system tumors is \< 30 days 10. Participate in other clinical studies within 30 days; 11. Failing to sign the informed consent form;