title: Exhaled carbon monoxide in childhood asthma.
abstract: OBJECTIVE
  Oxidative stress and inflammation induce the expression of heme oxygenase-1, which produces carbon monoxide (CO), and nitric oxide synthase, which produces nitric oxide (NO). Exhaled CO and NO levels are elevated in asthmatic patients and are decreased after corticosteroid treatment, suggesting that they may be useful as noninvasive markers of airway inflammation.
  
  
  METHODS
  We measured forced expiratory volume in the first second, PC(20), and exhaled CO and NO levels in 29 children (18 boys, mean age 11.5 +/- 0.53 years) with asthma of different severity and 40 nonsmoking children without asthma (21 boys, mean age 8.1 +/- 0.35 years). We also studied whether upper respiratory tract infections were associated with elevated exhaled CO.
  
  
  RESULTS
  Exhaled CO levels (ppm) were significantly higher (2.17 +/- 0.21) in children with persistent asthma compared with those in children with infrequent episodic asthma (1.39 +/- 0.18, P <.05) and healthy children (1.01 +/- 0.12, P <.001). The CO levels in children with infrequent episodic asthma and the normal control group, however, were not different. In contrast, exhaled NO levels (ppb) were higher in children with persistent asthma (24.2 +/- 5.9, P <.001) and infrequent episodic asthma (14.5 +/- 3.73, P <.05) than in normal subjects (5.1 +/- 0.24), but no significant difference was seen between the 2 asthmatic groups. In healthy children with upper respiratory tract infections (n = 12), exhaled CO concentrations were significantly elevated (2.16 +/- 0.33) during the acute symptomatic phase. No correlation was found between exhaled CO and forced expiratory volume in the first second or PC(20).
  
  
  CONCLUSIONS
  Noninvasive measurement of exhaled CO may provide complementary data for assessment of asthma control in children. However, elevated CO levels are nonspecific and may be found in association with an acute viral illness.
authors.affiliation: Department of Thoracic Medicine, National Heart and Lung Institute, London, United Kingdom.
authors.forename: C G
authors.initials: CG
authors.lastname: Uasuf
authors.forename: A
authors.initials: A
authors.lastname: Jatakanon
authors.forename: A
authors.initials: A
authors.lastname: James
authors.forename: S A
authors.initials: SA
authors.lastname: Kharitonov
authors.forename: N M
authors.initials: NM
authors.lastname: Wilson
authors.forename: P J
authors.initials: PJ
authors.lastname: Barnes
mesh_terms: D001249:Asthma / Q000175:diagnosis* / Q000378:metabolism; D001944:Breath Tests; D001985:Bronchial Provocation Tests; D002248:Carbon Monoxide / Q000032:analysis*; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D005541:Forced Expiratory Volume; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000032:analysis; D018384:Oxidative Stress; D012141:Respiratory Tract Infections / Q000378:metabolism
chemical_list: D009569:Nitric Oxide; D002248:Carbon Monoxide; D006419:Heme Oxygenase (Decyclizing)