title: Measurements of exhaled nitric oxide in healthy subjects age 4 to 17 years.
abstract: BACKGROUND
  Fractional exhaled nitric oxide (FE NO ) is used in monitoring of asthma.
  
  
  OBJECTIVE
  The aim of this multicenter study was to establish normal values of FE NO and assess feasibility in children with a standardized method and equipment approved for clinical use.
  
  
  METHODS
  FE NO was measured in healthy subjects of 4 to 17 years according to American Thoracic Society guidelines (single breath online, exhalation flow 50 mL/s) with a chemiluminescence analyzer (NIOX Exhaled Nitric Oxide Monitoring System, Aerocrine, Sweden) in 3 European and 2 US centers. Each child performed 3 acceptable nitric oxide measurements within 6 attempts and completed an extended International Study of Asthma and Allergy in Children questionnaire.
  
  
  RESULTS
  Measurement of FE NO was attempted in 522 children. Four hundred five children completed the study according to the protocol. Geometric mean FE NO in 405 children was 9.7 ppb, and the upper 95% confidence limit was 25.2 ppb. FE NO increased significantly with age, and higher FE NO was seen in children with self-reported rhinitis/conjunctivitis or hay fever. The success rate was age-dependent and improved from 40% in the children 4 years old to almost 100% from the age of 10 years. The repeatability of 3 approved measurements was 1.6 ppb (95% CI, 1.49-1.64 ppb).
  
  
  CONCLUSIONS
  FE NO in healthy children is below 15 to 25 ppb depending on age and self-reported atopy. Measurement of FE NO by NIOX is simple and safe and has a good repeatability. Feasibility depends on age and may be difficult in the preschool child.
authors.affiliation: The Copenhagen Studies of Asthma in Childhood Research Clinic, Copenhagen University Hospital, Gentofte, Denmark.
authors.forename: Frederik
authors.initials: F
authors.lastname: Buchvald
authors.forename: Eugenio
authors.initials: E
authors.lastname: Baraldi
authors.forename: Silvia
authors.initials: S
authors.lastname: Carraro
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gaston
authors.forename: Johan
authors.initials: J
authors.lastname: De Jongste
authors.forename: Mariëlle W H
authors.initials: MW
authors.lastname: Pijnenburg
authors.forename: Philip E
authors.initials: PE
authors.lastname: Silkoff
authors.forename: Hans
authors.initials: H
authors.lastname: Bisgaard
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001249:Asthma / Q000175:diagnosis* / Q000208:ethnology; D001944:Breath Tests / Q000295:instrumentation / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D003231:Conjunctivitis / Q000175:diagnosis; D005006:Ethnicity; D005060:Europe; D045853:Exhalation; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000032:analysis* / Q000592:standards; D012016:Reference Values; D015203:Reproducibility of Results; D012220:Rhinitis / Q000175:diagnosis; D012737:Sex Factors; D011795:Surveys and Questionnaires; D014481:United States
chemical_list: D009569:Nitric Oxide