Methodological issues related to exhaled nitric oxide measurement in children aged four to six years

Pediatr Pulmonol. 2005 Aug;40(2):97-104. doi: 10.1002/ppul.20249.


This study was designed to test five methodological issues related to measurement of fractional exhaled nitric oxide (FE(NO)) in children aged 4-6 years using commercially available apparatus. Participants attended two randomly selected schools. A respiratory questionnaire was completed. Measurements of FE(NO) were made on successive days, using a NIOX analyzer employing standard or modified methodologies. Ninety-one children participated in the study (mean age, 5.3 years; 46 boys). Using a standard methodology (n = 61), FE(NO) was successfully measured in 28 (46%) children, 1/12 aged 4 years, 12/25 aged 5 years, and 15/24 aged 6 years (trend test P = 0.01). On the first assessment, FE(NO) could be determined in more boys than girls (64% vs. 30%, respectively, P = 0.008), but this gender difference was not apparent on the second assessment. Exhaled NO was reproducible over a 24-hr period; the mean difference between repeated measurements of natural log (ln) FE(NO) was 0.016 parts per billion (ppb) (95% confidence limits, -0.479, 0.511), n = 20. Data from 35 assessments showed that values of FE(NO) did not alter over nine individual, successive measurements. Use of a modified methodology in 30 children increased success in obtaining FE(NO), but these values were unreliable. In conclusion, measurements of FE(NO) can be obtained in the majority of 5- and 6-year-old but not 4-year-old children. Exhaled NO measurements were reproducible over a 24-hr interval, and did not change over up to nine expiratory maneuvers in these young children.

MeSH terms

  • Age Factors
  • Asthma / diagnosis*
  • Breath Tests / methods
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Male
  • Nitric Oxide / analysis*
  • Reproducibility of Results
  • Sex Factors


  • Nitric Oxide