Electrical Activity of the Diaphragm and Respiratory Mechanics During NAVA (NAVAMECH)

Evaluation of the Relationship Between Electrical Activity of the Diaphragm and Respiratory Mechanics During Neurally Adjusted Ventilatory Assist in Lung Transplant Patients.

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.

Lung transplantation (LTx) is an important treatment option for select patients with end-stage pulmonary disease. In the early period following LTx a protective ventilatory strategy should be applied to reduce both ventilator-induced lung injury (VILI) and ventilator-induced diaphragm dysfunction (VIDD) after Lung Tranplantation (LTx). Neurally Adjusted Ventilatory Assist (NAVA) is an assisted ventilation mode in which neural inspiratory activity is monitored through the continuous recording of electrical activity of the diaphragm (EAdi) and then used to coordinate the respiratory support delivered by the ventilator. NAVA, because of its intrinsic properties (proportionality between respiratory drive and level of assist, prevention of diaphragm atrophy), could allow the aforementioned ventilatory strategy, however it may require the integrity of the pulmonary vagal afferent feedback in order to avoid volutrauma. So, the aim of the study is the evaluation of the physiological relationship between EAdi and tidal volume, driving pressure and mechanical power, at different levels of ventilatory assist, in the absence of pulmonary vagal afferent feedback, in early post-operative period after LTx.

Work of Breathing, Lung Transplantation, Neurally Adjusted Ventilatory Assist, Ventilator-Induced Lung Injury

NAVA ventilation: Assisted Ventilation Mode, synchronized, through EAdi catheter, with patient's inspiratory effort and proportional to respiratory drive

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)

Evaluation of the variations of Neuro-Mechanical Coupling (expressed as microVolt of EAdi /cmH2O of airway pressure Ratio) in response to different levels of ventilatory assist at different degrees of lung inflation. Neuro-Mechanical Coupling (NMC) (microvolt/cmH2O)

Evaluation of the variations of Neuro-ventilatory Efficiency (expressed as microvolt of EAdi / mL of Tidal Volume Ratio) in response to different levels of ventilatory assist at different degree of lung inflation. Neuro-Ventilatory Efficiency (NVE) (microvolt/mL)

Evaluation of the changes in the patient's neural breathing pattern (expressed as mL of Tidal Volume) at different levels of ventilatory assist. Respiratory rate (Breaths/min)

Ultrasound assessment of the changes of Diaphragm's Thickening Fraction at different levels of Positive End Expiratory Pressure and at different NAVA gains

Assesment of the total asynchrony index (double triggering + missed efforts + inspiratory trigger delay +short cycling + prolonged cycling)

Inclusion Criteria: Age > 18 y.o. Admission to ICU for post-operative monitoring after LTx Presence of spontaneous breathing activity Sedation titrated to a target RASS between 0 and -2 Written informed consent obtained Exclusion 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 retransplantation Failure to obtain a stable EAdi signal