Protective ventilatory strategy should be applied to reduce ventilator-induced lung injury (VILI) after Lung Transplantation (LTx) or in case of acute respiratory failure requiring invasive mechanical ventilation. 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 or during acute respiratory failure. Additional parameters will be collected: Pmus, Pocc, transpulmonary pressure etc.
Age > 18 y.o.
Admission to ICU for post-operative monitoring after LTx or acute respiratory failure needing invasive mechanical ventilation
Presence of spontaneous breathing activity
Sedation titrated to a target RASS between 0 and -2
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)
Single group
NAVA GROUP
DeviceNAVA ventilation: Assisted Ventilation Mode, synchronized, through EAdi catheter, with patient's inspiratory effort and proportional to respiratory drive
Electrical Activity of the Diaphragm (EAdi)
Evaluation of the variations of tidal volume Electrical Activity of the Diaphragm in response to different levels of ventilatory assist at different degrees of lung inflation (different Positive End Expiratory Pressure values). Electrical Activity of the Diaphragm (EAdi) (microVolt)
Tidal Volume (mL) and Respiratory rate (Breaths/min)
Evaluation of the changes in the patient's neural breathing pattern (expressed as mL of Tidal Volume) at different levels of ventilatory assist. Also patient's respiratory rate (Breaths/min) will be evaluated
Driving pressure (DP)
Evaluation of the variations of DP in response to different levels of ventilatory assist at different degrees of lung inflation. The driving pressure formula is DP = P\_plateau - PEEP. It represents the pressure difference between the plateau pressure (P\_plateau) and the positive end-expiratory pressure (PEEP) during mechanical ventilation. Unit: mmHg or cmH2O.
Occlusion Pression (Pocc)
Evaluation of the changes in the patient's respiratory effort (evaluated using Pocc) at different levels of ventilatory assist. The full breath occlusion pressure (Pocc) is the drop in airway-Pressre during a full occluded inspiratory effort. Unit: mmHg or cmH2O.
PaO2/FiO2 ratio
Evaluation of the changes in gas exchange, in particular in PaO2/FiO2 ratio, at different levels of ventilatory assist. The emogas analysis was collected from a peripheral artery.
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