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Neurally adjusted ventilatory assist versus proportional assist ventilation in prematurely born infants with evolving brochopulmonary dysplasia

Presented at the Neonatal Society 2018 Autumn Meeting (programme).

Hunt K1, Dassios T, Greenough A

King’s College London, UK. King’s College Hospital, UK

Background: Novel modes of neonatal ventilation such as neurally adjusted ventilatory assist (NAVA) and proportional assist ventilation (PAV) unload an adjustable proportion of the work of breathing from the infant to the ventilator. Both NAVA and PAV have been shown to have advantages over conventional ventilation, including improving oxygenation, respiratory muscle strength, and compliance (1,2,3). The two modes, however, have not been compared to each other in the neonatal population, hence this was the aim of our study.

Methods: Infants born at less than 32 weeks gestation and ventilated at or beyond one week of life were eligible for entry into the study if informed written parental consent was obtained. The study was approved by the London- South East NHS Research Ethics Committee. Infants received two hours of NAVA and two hours of PAV delivered in a random order. The inspired oxygen fraction was adjusted to maintain the oxygen saturations between 92 and 96%. Blood gas sampling was performed at the end of each two hour epoch and the oxygen index (OI) calculated and the respiratory rate and the electrical activity of the diaphragm were recorded.

Results: Eighteen infants with a median gestational age of 25.3 (range 23.6 – 30.3) weeks and median birthweight 750 (range 454 – 950) grams were studied at a median of 20.5 (range 8 – 58) postnatal days. All of the infants were subsequently diagnosed with BPD. Fifteen infants were receiving volume targeted ventilation prior to the study, with target tidal volumes between five and seven ml/kg. Nine infants received NAVA first. There were no significant differences in the OI between NAVA and PAV (median 7.2 (range 4.2 – 14.2) versus 6.8 (3.9 – 15), p=1.0), but the OI on both NAVA and PAV were significantly lower than the OI on baseline settings (8.6 (5.6 – 21.5), p=0.001, p<0.001 respectively). There were no significant differences between the expiratory tidal volume on NAVA, PAV and baseline settings (p=0.61), or between the electrical activity of the diaphragm (Edi) on NAVA, PAV, and baseline settings (p=0.33).

Conclusion: There were no significant differences in the oxygenation index between NAVA and PAV, but both were associated with superior oxygenation compared to that on baseline ventilation.

Corresponding author:

1. Shetty et al (2016), European Journal of Pediatrics 175:57-61
2. Bhat et al (2015), Arch Dis Child Fetal Neonatal Ed 100:F35-F38
3. Shetty et al (2017) European Journal of Pediatrics 176:509-513

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