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 (HF V) lead to a more pronounced improvement in oxygenation than iNO durin g conventional ventilation? We report two cases of newborn infants wit h profound hypoxaemia, who did not respond with an increase in arteria l oxygenation following iNO therapy during conventional mechanical ven tilation. The first infant was a term neonate with persistent pulmonar y hypertension of the newborn (PPHN) following postnatal hypoxia, the second patient a premature infant of 29 weeks of gestation with PPHN s econdary 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. S hortly after the initiation of HFV a second trial of iNO was started. Both infants responded favourably to iNO with a marked and sustained i ncrease in arterial oxygenation and absent right-to-left shunting via the ductus arteriosus and the foramen ovale. We conclude that the favo urable response to inhaled nitric oxide is dependent on the degree of long expansion and is more readily achieved by the use of high-frequen cy ventilation than conventional ventilation.