The endogenous production of nitric oxide (NO) in the upper airways is known to be high, but reports of the exact level vary, especially in newborn infants. Currently there is still no standard methodology for nasal NO measurements in neonates. In this study, we compared the levels of NO from the nasal cavity, and from the lower respiratory tracts in intubated infants together with the differences in nasal NO before and after extubation. A total of 35 intubated infants were enrolled in the study. The sampling was conducted with a fast-response chemoluminescence analyzer using the on-line tidal breathing techniques. The levels of NO in the nasal cavity were sampled using two different methods, namely nasal catheterization (Group 1), and nasal occlusion (Group 2). In both groups, the NO levels in the nasal cavity were found to be significantly higher than in the lower airway (P < 0.001). After extubation, the concentration of nasal NO in Group 1 was found to be significantly lower than before extubation (P < 0.05). There was no difference found between the levels of nasal NO in Group 2 before and after extubation (P = 0.95). Generally speaking, the concentrations of nasal NO in Group 2 were significantly higher than in Group 1 after extubation (P < 0.05). For the sample that used nasal occlusion, the nasal NO levels were more stable before and after extubation and the concentration was not affected by the breathing pattern or crying. The infants were more comfortable as well. We therefore conclude that nasal occlusion is a better method for measuring the levels of nasal NO in infants and neonates.
(c) 2008 Wiley-Liss, Inc.