Comparative Effects of Variable Pressure Support, NAVA and PAV

Comparative Effects of Variable Pressure Support, Neurally Adjusted Ventilatory Assist (NAVA) and Proportional Assist Ventilation (PAV) on the Variability of the Breathing Pattern and on Patient Ventilator Interaction

Experimental animal data suggest that increasing breathing pattern variability in mechanical ventilation could be beneficial. Variable ventilation can be induced through the following modes: Neurally Adjust Ventilatory Assist (NAVA), Proportional Assist Ventilation (PAV) and Variable-Pressure Support Ventilation (V-PSV). These modes have not yet been compared to each other. Pilot observations in our department suggest a feasibility in patients. The objectives of the study are to compare the impact of PSV, NAVA, PAV and V-PSV on the variability of the breathing pattern, patient-ventilator asynchrony, risk of lung overdistension, gas exchange, and repartition of ventilation.

Cross-over, prospective, randomized controlled monocentric trial . Patients on pressure support ventilation will be ventilated with PSV, NAVA, PAV, and V-PSV (in a randomized sequence). In each mode the level of assistance will be set to achieve a similar tidal volume of 6-8 ml/kg. The following data will be measured and recorded: airway flow and pressure, electrical activity of the diaphragm (EAdi), blood gases, electrical impedance tomography, end tidal partial pressure in carbon dioxide (PEtCO2). Will be calculated: the coefficient of variation (CV, standard deviation (SD)/mean) of the peak pressure (Ppeak), EAdi and of the main descriptors of the breathing pattern, the prevalence of the main patient-ventilator asynchronies, the prevalence of tidal volume (VT) >10ml/kg, ventrodorsal repartition of ventilation and inhomogeneity index, dead space

mechanical ventilation, pressure support ventilation, NAVA, PAV, variable ventilation, patient ventilator asynchrony

This is a crossover study in which each patient will be ventilated in the following modes of mechanical ventilation: Pressure Support Ventilation (PSV), Neurally Adjusted Ventilator Assist (NAVA), Proportional assist ventilation (NAVA) and variable Pressure Support Ventilation (Variable-PSV), in a randomised order.

Each patient enrolled in the study will be ventilated in all the following modes: PSV, NAVA, PAV and variable PSV

Coefficient of variation (standard deviation/mean) of the electrical activity of the diaphragm (EAdi)

asynchrony index (composite outcome, that includes double triggering, auto triggering and ineffective efforts) )

Ratio of arterial oxygen partial pressure to fractional inspired oxygen (PaO2/FiO2), arterial carbon dioxide pressure (PaCO2)

Inclusion Criteria: patient on mechanical ventilation for >48 h estimated duration of mechanical ventilation >24h hemodynamic stability Exclusion Criteria: pregnancy impossibility to insert an EAdi catheter neuromuscular disease, phrenic nerve lesions