NAVA vs PSV Ventilation During Weaning From Mechanical Ventilation in Children After Liver Transplantation

Twelve pediatric patients underwent liver transplantation and admitted during postoperative period in PICU will be studied. They will be endotracheally intubated and spontaneously triggering the mechanical ventilator. In each patient enrolled a specially manufactured nasogastric tube will be inserted. This nasogastric tube is equipped with ten electrodes. The correct position of the nasogastric tube (and of electrodes) will be confirmed checking the good quality of Edi trace with the P waves displayed by the central electrodes on monitor of Servo I Ventilator (Maquet). All the patients will be ventilated using ventilators with NAVA option (Servo-I, Maquet Critical Care, Sweden). After a stabilization period in Pressure Support Ventilation (PSV) according with the attending physician, each patient will be studied for a duration of 2 hours, divided in three trials of 40-minutes (first 30 minutes to washout from the effects of previous ventilation mode and during the last 10 minutes the results will be recorded). Each patient will be randomized for ventilation mode sequence (PSV/NAVA/PSV or NAVA/PSV/NAVA). The patient tracings of flow, airway pressure, electrical activity of diaphragm for the patient-ventilator interaction analysis, blood gas analysis and cardiovascular parameters will be recorded during each trial.