Changes in alveolar-arterial oxygen difference and oxygenation index during low-dose nitric oxide inhalation in 15 newborns with severe respiratory insufficiency

We evaluated changes in alveolar-arterial oxygen differences (AaDO2) and oxygenation index (OI) during inhalation of low-dose nitric oxide (INO) in 15 newborns with severe respiratory insufficiency: congenital diaphragmatic hernia (CDH) - 6, asphyxial lung disease - 4, meconium aspiration syndrome (MAS) - 2, respiratory distress syndrome - 2, persistent pulmonary hypertension of newborn - 1. Their mean birth weight was 2522 g (1030- 3200 g, SD ± 575), mean gestational age 36 weeks (29-39 weeks, SD ± 3.2), mean initial AaDO2 = 607 mm Hg (574-628 mm Hg, SD ± 14) and mean initial OI = 32 (6-57, SD ± 12). INO was performed using the Pulmonox system (Messer Griesheim, Austria) at conventional regimens of mechanical ventilation. The initial value of 20 ppm nitric oxide (NO) was decreased 6 h later, first to 15 ppm and then, as quickly as possible, to 3 ppm. The mean inhalation period was 51 h (6-131 h, SD ± 42). The initial values of AaDO2 and OI decreased significantly within the first 6 h of INO (P < 0.001). After the first 6 h, 4 patients died: 1 with MAS of an extrapulmonary cause and 3 CDH patients because of pulmonary hypoplasia. In the remaining 11 patients the decrease in AaDO2 and OI during the first 24 h of INO was highly significant (P < 0.0001). Conclusion In a heterogeneous group of 15 newborns with severe respiratory insufficiency, the initial AaDO2 and OI decreased significantly within the first 6 h of INO. [PUBLICATION ABSTRACT]