Neurally adjusted ventilatory assist and proportional assist ventilation both improve patient-ventilator interaction

Introduction: The objective was to compare the impact of three assistance levels of different modes of mechanical ventilation; neurally adjusted ventilatory assist (NAVA), proportional assist ventilation (PAV), and pressure support ventilation (PSV) on major features of patient-ventilator interaction. Methods: PSV, NAVA, and PAV were set to obtain a tidal volume (V-T) of 6 to 8 ml/kg (PSV100, NAVA(100), and PAV(100)) in 16 intubated patients. Assistance was further decreased by 50% (PSV50, NAVA(50), and PAV(50)) and then increased by 50% (PSV150, NAVA(150), and PAV(150)) with all modes. The three modes were randomly applied. Airway flow and pressure, electrical activity of the diaphragm (EAdi), and blood gases were measured. VT, peak EAdi, coefficient of variation of VT and EAdi, and the prevalence of the main patient-ventilator asynchronies were calculated. Results: PAV and NAVA prevented the increase of VT with high levels of assistance (median 7.4 (interquartile range (IQR) 5.7 to 10.1) ml/kg and 7.4 (IQR, 5.9 to 10.5) ml/kg with PAV(150) and NAVA(150) versus 10.9 (IQR, 8.9 to 12.0) ml/kg with PSV150, P < 0.05). EAdi was higher with PAV than with PSV at level(100) and level(150). The coefficient of variation of VT was higher with NAVA and PAV (19 (IQR, 14 to 31)% and 21 (IQR 16 to 29)% with NAVA(100) and PAV(100) versus 13 (IQR 11 to 18)% with PSV100, P < 0.05). The prevalence of ineffective triggering was lower with PAV and NAVA than with PSV (P < 0.05), but the prevalence of double triggering was higher with NAVA than with PAV and PSV (P < 0.05). Conclusions: PAV and NAVA both prevent overdistention, improve neuromechanical coupling, restore the variability of the breathing pattern, and decrease patient-ventilator asynchrony in fairly similar ways compared with PSV. Further studies are needed to evaluate the possible clinical benefits of NAVA and PAV on clinical outcomes.