Exhaled nitric oxide in neonates with or without hypoxemic respiratory failure.

BACKGROUND Exhaled nitric oxide (eNO) is one of the airway condensate derived markers, reflecting mainly airway inflammation in asthma and other lung diseases. The changes of eNO levels as pathophysiology of neonatal hypoxemic respiratory failure (HRF) in early postnatal life have not been thoroughly studied. The present study was to establish a method for measuring eNO concentrations in neonates with or without HRF. METHODS Twenty-two newborn infants with HRF and 26 non-NRF controls were included within the first 24 hours of postnatal life. Their eNO levels were detected with a rapid-response chemiluminescence analyzer daily during the first week of their postnatal life, and lung mechanics and gas exchange efficiency were monitored at the same time, such as pulse oxygen saturation (SpO2), inspired fraction of oxygen (FiO2) and other parameters. RESULTS During the first two days of postnatal life, eNO values of HRF neonates were significantly higher than those of the control neonates (day 1, 7.9±3.2 vs. 5.8±1.8 parts per billion [ppb], P<0.05; day 2, 8.8±3.2 vs. 6.0±2.4 ppb, P<0.05), but there were no significant differences in the following days. With SpO2/FiO2 increasing, difference of eNO values between the HRF and non-HRF neonates became narrowed, but there was still a two-fold difference of eNO/[SpO2/(FiO2×100)] on days 5-7. CONCLUSION We established a method for measuring eNO and found difference in neonates with or without HRF, which diminished with prolonged postnatal days, reflecting pathophysiological characteristics of HRF.