Nasal and lower airway levels of nitric oxide in prematurely born infants.

Abstract

Nitric oxide (NO) is produced by various cells in the respiratory tract, but the majority is released from the paranasal sinuses in adults. The paranasal sinuses in infants are only partially pneumatised. Thus, nasal NO would be predicted to be low in infants measured soon after birth and/or born very prematurely; this has implications for the measurement of exhaled NO and interpretation of the results obtained. To determine whether nasal NO could be detected in very immature infants, particularly soon after birth, and whether nasal or lower airway NO levels were influenced by gestational age or postnatal age. Fifteen infants, with median gestational age of 27 weeks (range 25-32 weeks). Nasal and lower airway NO measurements were attempted on days 1, 3, 5, 7, 14, 21, and 28 after birth. Measurements were only made while the infants remained ventilated. Nasal NO was sampled directly from the nasal space and lower airway. NO was sampled from a catheter positioned so that its tip lay at the lower end of the endotracheal tube. Nasal NO was detected in all infants on all study occasions and the levels were greater than those from the lower airway. Nasal and lower airway NO levels did not correlate significantly with gestational age, but lower airway NO levels correlated with postnatal age (r=0.86, p=0.014). Even in very immature infants examined in the first day after birth, care must be taken to avoid contamination with nasal NO, if lower airway levels are to be accurately assessed.