P2C072: Implementation of a Physiologic Ventilator Strategy to Reduce Utilization of Nitric Oxide and ECMO in Infants with Congenital Diaphragmatic Hernia

Background: Congenital Diaphragmatic Hernia (CDH) is characterized by pulmonary hypoplasia, pulmonary hypertension, and biventricular cardiac dysfunction. In many centers including our own, initial pre-operative management had included intensive ventilation and aggressive treatment of pulmonary hypertension. Published literature has revealed that neither high ventilator pressures nor nitric oxide (iNO) reduce mortality or the use of extracorporeal membrane oxygenation (ECMO), and national experts have recommended lower pressures in order to avoid hyperinflation and optimize gas exchange. The objective of this comparative retrospective study is to evaluate the use of a gentle ventilation strategy on the need for escalation to iNO and ECMO.

Methods: We revised CDH pre-operative management guidelines with new initial ventilator settings to match the physiology of lung hypoplasia. Prior guidelines suggested a mode of synchronized intermittent mandatory ventilation (SIMV) with peak inspiratory pressures (PIP) of 22-24cmH2O/positive end-expiratory pressure (PEEP) 5 cmH2O or high-frequency oscillator mean airway pressure (MAP) 12-13cmH2O /Amplitude 30-34. New initial settings include a PEEP of 4cmH2O, and a tidal volume guarantee of 4ml/kg. The current approach allows PIPs as low as 14-15 as compliance postnatally rises. We now use the assist-control mode to allow a “patient-driven rate,” complemented by an inspiratory time of 0.3sec to prevent breath-stacking. We hypothesized that this strategy would allow for improved V/Q matching and reduce the clinical symptoms of pulmonary hypertension. Under the new guidelines, iNO is initiated if preductal saturation cannot be maintained >90% with oxygen alone, whereas prior guidelines recommended treatment of a pre/post ductal differential saturation of >5%. Our primary outcome is the need for ECMO, with secondary outcomes of iNO usage and days of mechanical ventilation. Data was collected from 2016-current at our single center, following Institutional Review Board regulations. Data analysis was performed using GraphPad Prism 9.5.1.

Results: Data were collected from 50 infants prior to guideline revision and is ongoing post-revision, with six infants to date. Demographic data showed no difference between groups regarding: gestational age, birthweight, sex, side of hernia, observed/expected lung-to-head ratio, incidence of liver herniation, or history of fetal endoscopic tracheal occlusion (FETO) intervention. The incidence of ECMO decreased from 46% pre-revision to 0% post-revision (p=0.03, see figure 1). The use of iNO decreased from 82% pre-revision to 17% post-revision (p=0.0003). Pre-revision, 16/50 infants were never extubated (32%; 14 deaths, 2 tracheostomies). Post-revision, 100% of infants have survived (p=0.13) and have been extubated (p=0.1). Of those extubated, the total ventilator days decreased from a mean of 30.5 days to 9.8 days (p=0.08).

Conclusion: Preliminary data for our physiologic CDH ventilator strategy have shown significantly reduced ECMO and iNO utilization. This strategy is also associated with an increased likelihood of extubation, and a reduced number of mechanical ventilator days.