부산대학교 도서관

Spirometry in adult subjects can induce a fall in concentration of exhaled nitric oxide (FENO). Scarce information is available on the FENO decrease after spirometry or after other forced lung-function maneuvers in children. We compared changes in FENO induced by repeated spirometry and testing of maximal expiratory pressures (PEmax). Twenty-four sex- and agematched children aged 9-18 years (mean age ± SD, 13.3 ± 2.8 years; 12 healthy, 12 asthmatic) were allocated to 1-week-apart sessions of repeated maneuvers of either forced vital capacity (FVC) or PEmax. Baseline FENO measurements were followed by FVC or PEmax maneuvers every 15 min for 45 min, whereas FENO was measured at each step for 60 min. After repeated PEmax but not after FVC maneuvers, FENO values decreased significantly from baseline in both groups. In healthy children, geometric mean FENO (95% confidence intervals) decreased from 9.1 (7.0-11.8) ppb at baseline to 8.2 (6.3-10.6) ppb at 15 min and 7.7 (5.6-10.6) ppb at 30 min (P< 0.05 and P< 0.01, respectively), and remained unchanged at 45 and 60 min. In asthmatic children, FENO levels fell from 21.6 (13.3-34.9) ppb at baseline to 15.1 (9.1-25.1) ppb at 15 min and remained low at 30, 45, and 60 min: 17.8 (10.7-29.5) ppb, 17.5 (10.2-30.1) ppb, and 17.6 (10.6-29.2) ppb, P< 0.01, for all differences from baseline. Repeated PEmax and FVC maneuvers increased FENO variability, as compared with repeated FENO measurements alone. Previous forced lung-function maneuvers may affect FENO measurements in children. Although PEmax testing has a greater influence than spirometry on FENO levels in children, both procedures should be avoided before measuring FENO.