title: Comparison of alveolar nitric oxide concentrations using two different methods for assessing small airways obstruction in asthma.
abstract: OBJECTIVE
  Fractional exhaled nitric oxide (F(E) NO) is considered a potentially useful biomarker for airway inflammation. A two-compartment model (2CM) of pulmonary NO dynamics has been used for the evaluation of bronchial NO flux (J'awNO) and alveolar NO concentration (C(A) NO) in asthmatic patients. Recently, the trumpet shape of the airway tree and axial diffusion (TMAD) model has been reported as a modification of the 2CM. This study was designed to determine the validity of C(A) NO measurement using the TMAD model for assessing small airways inflammation in asthma.
  
  
  METHODS
  A total of 52 asthmatic patients and 12 normal control subjects were included in the study. Methacholine inhalation challenge and pulmonary function tests, sputum induction, and exhaled NO measurements at several flow rates were performed. J'awNO and C(A) NO were calculated using both the 2CM (C(A) NO( 2CM) , J'awNO( 2CM) ) and TMAD models (C(A) NO( TMAD) , J'awNO( TMAD) ).
  
  
  RESULTS
  Both J'awNO (J'awNO( 2CM) and J'awNO( TMAD) ) and C(A) NO (C(A) NO( 2CM) and C(A) NO( TMAD) ) were significantly higher in asthmatic patients than in control subjects. C(A) NO( 2CM) was significantly correlated with FEV(1) /FVC (r = -0.35, P = 0.01), FEF(25-75) (r = -0.45, P < 0.001) and sputum eosinophils (r = 0.32, P = 0.02). In contrast, C(A) NO( TMAD) was significantly correlated with FEF(25-75) (r = -0.42, P = 0.002) but not with FEV(1) /FVC or sputum eosinophils.
  
  
  CONCLUSIONS
  C(A) NO( TMAD) is more specific as an indicator of small airways obstruction than C(A) NO( 2CM) . Assessment of small airways obstruction using the TMAD model may clarify the role of the small airways in the pathogenesis of asthma.
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Osaka City University, Osaka, Japan. daiki_koba@med.osaka-cu.ac.jp
authors.forename: Daiki
authors.initials: D
authors.lastname: Kobayashi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Tochino
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kanazawa
authors.forename: Yukikazu
authors.initials: Y
authors.lastname: Ichimaru
authors.forename: Shigenori
authors.initials: S
authors.lastname: Kyoh
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Asai
authors.forename: Kazuto
authors.initials: K
authors.lastname: Hirata
mesh_terms: D000328:Adult; D001249:Asthma / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D015415:Biomarkers / Q000378:metabolism; D001980:Bronchi / Q000378:metabolism*; D001985:Bronchial Provocation Tests / Q000379:methods*; D016022:Case-Control Studies; D004804:Eosinophils / Q000473:pathology; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism*; D012129:Respiratory Function Tests / Q000379:methods*; D013183:Sputum / Q000166:cytology; D014797:Vital Capacity / Q000502:physiology
chemical_list: D015415:Biomarkers; D009569:Nitric Oxide