Electrical Activity of the Diaphragm and Respiratory Mechanics During NAVA

Protective ventilatory strategy should be applied to reduce both ventilator-induced lung injury (VILI) and ventilator-induced diaphragm dysfunction (VIDD) after Lung Transplantation (LTx). Neurally Adjusted Ventilatory Assist (NAVA) is an assisted ventilation mode in which respiratory support is coordinated by the electrical activity of the diaphragm (EAdi). Aim of the study is to assess the physiological relationship between neural respiratory drive as assessed by EAdi and tidal volume, driving pressure and mechanical power, at different levels of ventilatory assist, in the absence of pulmonary vagal afferent feedback.

Inclusion Criteria:Age > 18 y.o.Admission to ICU for post-operative monitoring after LTxPresence of spontaneous breathing activitySedation titrated to a target RASS between 0 and -2Written informed consent obtainedExclusion Criteria:Contraindication to nasogastric tube insertion (gastroesophageal surgery in the previous 3 months, gastroesophageal bleeding in the previous 30 days, history of esophageal varices, facial trauma)Increased risk of bleeding with nasogastric tube insertion, due to severe coagulation disorders and severe thrombocytopenia ( i.e., INR > 2 and platelets count < 70.000/mm3)Severe hemodynamic instability (noradenaline > 0.3 μg/kg/min and/or use of vasopressin)Postoperative extracorporeal respiratory support (ECMO)Pre-operative reconditioning of the transplanted lungs by means of ex-vivo lung perfusion (EVLP)Lung retransplantationFailure to obtain a stable EAdi signal