title: The fraction of NO in exhaled air and estimates of alveolar NO in adolescents with asthma: methodological aspects.
abstract: BACKGROUND
  This study investigated the oral contribution to exhaled NO in young people with asthma and its potential effects on estimated alveolar NO (Calv(NO) ), a proposed marker of inflammation in peripheral airways. Secondary aims were to investigate the effects of various exhalation flow-rates and the feasibility of different proposed adjustments of (Calv(NO) ) for trumpet model and axial diffusion (TMAD).
  
  
  METHODS
  Exhaled NO at flow rates of 50-300 ml/sec, and salivary nitrite was measured before and after antibacterial mouthwash in 29 healthy young people (10-20 years) and 29 with asthma (10-19 years). Calv(NO) was calculated using the slope-intercept model with and without TMAD adjustment.
  
  
  RESULTS
  Exhaled NO at 50 ml/sec decreased significantly after mouthwash, to a similar degree in asthmatic and healthy subjects (8.8% vs. 9.8%, P = 0.49). The two groups had similar salivary nitrite levels (56.4 vs. 78.4 µM, P = 0.25). Calv(NO) was not significantly decreased by mouthwash. Calv(NO) levels were similar when flow-rates between 50-200 or 100-300 ml/sec were used (P = 0.34 in asthmatics and P = 0.90 in healthy subjects). A positive association was found between bronchial and alveolar NO in asthmatic subjects and this disappeared after the TMAD-adjustment. Negative TMAD-adjusted Calv(NO) values were found in a minority of the subjects.
  
  
  CONCLUSIONS
  Young people with and without asthma have similar salivary nitrite levels and oral contributions to exhaled NO and therefore no antibacterial mouthwash is necessary in routine use. TMAD corrections of alveolar NO could be successfully applied in young people with asthma and yielded negative results only in a minority of subjects.
authors.affiliation: Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden. charlotte.heijkenskjold.rentzhog@kbh.uu.se
authors.forename: Charlotte
authors.initials: C
authors.lastname: Heijkenskjöld-Rentzhog
authors.forename: Kjell
authors.initials: K
authors.lastname: Alving
authors.forename: Pia
authors.initials: P
authors.lastname: Kalm-Stephens
authors.forename: Jon O
authors.initials: JO
authors.lastname: Lundberg
authors.forename: Lennart
authors.initials: L
authors.lastname: Nordvall
authors.forename: Andrei
authors.initials: A
authors.lastname: Malinovschi
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000503:physiopathology*; D001944:Breath Tests / Q000379:methods*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D009067:Mouthwashes / Q000627:therapeutic use; D009569:Nitric Oxide / Q000032:analysis*; D009573:Nitrites / Q000032:analysis; D011650:Pulmonary Alveoli / Q000737:chemistry* / Q000503:physiopathology*; D012463:Saliva / Q000737:chemistry; D055815:Young Adult
chemical_list: D009067:Mouthwashes; D009573:Nitrites; D009569:Nitric Oxide