High-frequency ventilation augments the effect of inhaled nitric oxide in persistent pulmonary hypertension of the newborn

Does inhaled nitric oxide (iNiO) during high-frequency ventilation (HFV) lead to a more pronounced improvement in oxygenation than iNO during conventional ventilation? We report two cases of newborn infants with profound hypoxaemia, who did not respond with an increase in arterial oxygenation following iNO therapy during conventional mechanical ventilation. The first infant was a term neonate with persistent pulmonary hypertension of the newborn (PPHN) following postnatal hypoxia, the second patient a premature infant of 29 weeks of gestation with PPHN secondary to lung hypoplasia and perinatal asphyxia, After the initial failure of iNO we switched both neonates to HFV without NO, which did not lead to a significant improvement of oxygenation in either case. Shortly after the initiation of HFV a second trial of iNO was started. Both infants responded favourably to iNO with a marked and sustained increase in arterial oxygenation and absent right-to-left shunting via the ductus arteriosus and the foramen ovale. We conclude that the favourable response to inhaled nitric oxide is dependent on the degree of long expansion and is more readily achieved by the use of high-frequency ventilation than conventional ventilation.