Exhaled nitric oxide and tracheal endothelin-1 in preterm infants with and without RDS^†

We measured exhaled nitric oxide and tracheal aspirate endothelin-1 to determine relationships between these substances and alterations in pulmonary gas exchange during respiratory distress syndrome (RDS) in comparison to those obtained from control preterm infants without RDS. Eight infants with RDS had measurements made at 24 hr and again at 48–72 hr. Eight control infants were studied once at 24–48 hr of life. Exhaled gas was analyzed on-line, and minute excretion of NO (V̇_NO) was calculated. ET-1 was determined by immunoassay. Median V̇_NO at 24 hr in RDS was 0.405 nl/min/kg (range, 0.30 –0.79), which subsequently declined by 48–72 hr to 0.166 nl/min/kg (P < 0.01). The V̇_NO in RDS infants was significantly higher than time-matched V̇_NO in controls, with a median of 0.099 nl/min/kg (range, 0.03–0.27; P < 0.001). ET-1 was not correlated with initial V̇_NO in the RDS or control patients. In conclusion, in RDS, V̇_NO decreases as gas exchange improves. ET-1 is detectable in tracheal aspirate samples in both groups of infants. Pediatr Pulmonol. 2003; 36:421–426. © 2003 Wiley-Liss, Inc.