A pilot study of inhaled nitric oxide in preterm infants treated with nasal continuous positive airway pressure for respiratory distress syndrome

Objective: To explore the acute effects of inhaled nitric oxide (iNO) on oxygenation, respiratory rate, and CO2 levels in spontaneously breathing preterm infants treated with nasal continuous positive airway pressure (nCPAP) for moderate respiratory distress syndrome (RDS). Design and setting: Randomized, prospective, double-blind, cross-over study in the neonatal intensive care units of a university hospital. Patients: 15 infants treated for RDS, with a median gestational age of 32 weeks (27-36), birth weight 1940 g (1100-4125), and postnatal age at the beginning of study 23 h (3-91). nCPAP pressure was kept constant at 4.3 cmH(2)O (3.4-5.1). Interventions: We examined effects on gas exchange and vital signs during a 30-min exposure to 10 ppm iNO or placebo gas (nitrogen). Results: Before administering test gases the baseline arterial to alveolar oxygen tension ratio (aAPO(2)) was 0.19 +/- 0.06. aAPO(2) remained unchanged during placebo but increased to 0.22 +/- 0.05 (+20%) during iNO exposure. Respiratory rate and arterial carbon dioxide tension remained unchanged, as did heart rate, blood pressure, and methemoglobin. Follow-up at 30 days of age showed no deaths, delayed morbidity, or need for supplemental oxygen. Conclusions: Adding 10 ppm nitric oxide to nasal CPAP treatment in preterm infants suffering from RDS results in a moderate but statistically significant improvement in oxygenation, with no effect on respiratory drive or systemic circulatory parameters.