ENDOGENOUS NITRIC-OXIDE IN THE UPPER AIRWAYS OF PREMATURE AND TERM INFANTS

Concentrations of endogenous nitric oxide (NO) were measured in premat ure (n = 18) and term infants (n = 7). Nasal gas was aspirated continu ously and after timed occlusions, 15 s and 60 s, by a fast-response ch emiluminescence analyser. The sampling flow rate was 20 ml min(-1). Ty pical NO recordings consisted of plateaux and postocclusive peaks. In term infants peak NO concentrations (60 s occlusion) were 2.71 +/- 0.4 4 parts per million (ppm) within 10 min after birth, increasing (p < 0 .05) to 3.81 +/- 0.25 ppm at 4-7 d postnatally. Peak NO values (15 a o cclusion) averaged 1.22 +/- 0.16 ppm in premature infants (postconcept ional age 25-37 weeks, body weight 623-2844 g) and the NO concentratio ns increased significantly with postconceptional age (p < 0.05). Nasal excretion rate, estimated from plateau NO concentrations and sampling flow rate, was 0.10 +/- 0.01 nmol min(-1) kg(-1) in both groups. We c onclude that premature and term newborn infants excrete considerable a mounts of NO in the upper airways, with hitherto not fully known funct ions.