Tidal exhaled nitric oxide in healthy, unsedated newborn infants with prenatal tobacco exposure

Tidal fractional exhaled nitric oxide (FENO) changes were investigated in healthy, unsedated infants with or without prenatal tobacco exposure. Tidal flow (V)over dot, FENO, and CO2 were measured in 20 healthy, unsedated infants [age: 25-58 days, length: 56.5+/-2.5 (SE) cm]. NO Output ((V)over dotNO) was calculated (V)over dot NO = FENO x (V)over dot. Two approaches were used to investigate within-breath changes of FENO and (V)over dotNO. First, we identified phases II and III from the expiratory capnogram. Second, we divided expiration into time-based quartiles. Tidal FENO (range: 14.5+/-1.6 to 17.6-/+2.1 parts/billion: quartile 4 and phase II, respectively) was not different between portions and exhibited significant negative (V)over dot dependence. (V)over dotNO was significantly dependent on the expiratory portion, with quartile 4 being significantly lower than the remaining expiratory portions. Infants exposed to prenatal cigarette smoke (n=7) exhibited significantly lower FENO and (V)over dotNO compared with nonexposed (n=13) infants. We conclude that tidal FENO is (V)over dot dependent and that (V)over dotNO may be a more suitable outcome parameter in variable (V)over dot conditions. Prenatal tobacco exposure resulted in a decreased FENO and (V)over dotNO in infants.