Chronic lung disease (CLD) is an inflammatory disorder; in patients with other inflammatory disorders exhaled nitric oxide (NO) levels are elevated. The aim of this study was to test the hypothesis that prematurely born infants with CLD would have elevated exhaled NO levels compared to those without CLD and healthy term-born infants. Ten infants with CLD (median gestational age 26 weeks; CLD group), ten infants without CLD (median gestational age 32 weeks; non-CLD group) and ten term-born infants (term group) were examined at post-conceptional ages between 36 and 45 weeks. NO levels were measured during spontaneous tidal breathing. A facemask was positioned over the infant's nose and mouth and a sampling catheter was inserted through a small leak-free valve into the facemask. To measure nasal NO, the tip of the sampling catheter was placed in the nasal space and to measure facemask NO, the catheter tip was positioned inside the facemask at the infant's lips. Nasal compared to facemask NO levels were higher in all three groups (CLD; non-CLD; term: P=0.017, P=0.012 and P=0.017, respectively). The CLD group had higher peak nasal and facemask NO levels than the non-CLD ( P=0.011 and P=0.034 respectively) and the term ( P=0.005 and P=0.01 respectively) infants. Regression analysis demonstrated that facemask NO levels were significantly related to CLD, independent of gestational, post-natal and post-conceptional age ( P=0.006).
Conclusion: our results suggest that exhaled nitric oxide levels are elevated in chronic lung disease infants. Facemask measurement of nitric oxide levels might be a potentially useful method to monitor infants with chronic lung disease.