King's College London

Both proportional assist ventilation (PAV) and neurally-adjusted ventilatory assist (NAVA) provide pressure support synchronised throughout the respiratory cycle proportional to the patient’s respiratory demand. Our aim was to compare the effect of these two modes on oxygenation in infants with evolving or established bronchopulmonary dysplasia. Two-hour periods of PAV and NAVA were delivered in random order to 18 infants born less than 32 weeks of gestation. Quasi oxygenation indices (“OI”) and alveolar-arterial (“A-a”) oxygen gradients at the end of each period on PAV, NAVA and baseline ventilation were calculated using capillary blood samples. The mean “OI” was not significantly different on PAV compared to NAVA (7.8 (standard deviation (SD) 3.2) versus 8.1 (SD 3.4), respectively, p=0.70), but lower on both than on baseline ventilation (mean baseline “OI” 11.0 (SD 5.0)), p=0.002, 0.004 respectively). The “A-a” oxygen gradient was higher on PAV and baseline ventilation than on NAVA (20.8 (SD 12.3) and 22.9 (SD 11.8) versus 18.5 (SD 10.8) kPa, p= 0.015, <0.001 respectively). Conclusion:Both NAVA and PAV improved oxygenation compared to conventional ventilation. There was no significant difference in the mean “OI” between the two modes, but the mean “A-a” gradient was better on NAVA.