title: Changes in the highest frequency of breath sounds without wheezing during methacholine inhalation challenge in children.
abstract: OBJECTIVE
  It is difficult for clinicians to identify changes in breath sounds caused by bronchoconstriction when wheezing is not audible. A breath sound analyser can identify changes in the frequency of breath sounds caused by bronchoconstriction. The present study aimed to identify the changes in the frequency of breath sounds during bronchoconstriction and bronchodilatation using a breath sound analyser.
  
  
  METHODS
  Thirty-six children (8.2 +/- 3.7 years; males : females, 22 : 14) underwent spirometry, methacholine inhalation challenge and breath sound analysis. Methacholine inhalation challenge was performed and baseline respiratory resistance, minimum dose of methacholine (bronchial sensitivity) and speed of bronchoconstriction in response to methacholine (Sm: bronchial reactivity) were calculated. The highest frequency of inspiratory breath sounds (HFI), the highest frequency of expiratory breath sounds (HFE) and the percentage change in HFI and HFE were determined. The HFI and HFE were compared before methacholine inhalation (pre-HFI and pre-HFE), when respiratory resistance reached double the baseline value (max HFI and max HFE), and after bronchodilator inhalation (post-HFI and post-HFE).
  
  
  RESULTS
  Breath sounds increased during methacholine-induced bronchoconstriction. Max HFI was significantly greater than pre-HFI (P < 0.001), and decreased to the basal level after bronchodilator inhalation. Post-HFI was significantly lower than max HFI (P < 0.001). HFI and HFE were also significantly changed (P < 0.001). The percentage change in HFI showed a significant correlation with the speed of bronchoconstriction in response to methacholine (P = 0.007).
  
  
  CONCLUSIONS
  Methacholine-induced bronchoconstriction significantly increased HFI, and the increase in HFI was correlated with bronchial reactivity.
authors.affiliation: Department of Pediatrics, Minami Wakayama Medical Center, Tanabe, Japan. gd6c-hbkw@asahi-net.or.jp
authors.forename: Chizu
authors.initials: C
authors.lastname: Habukawa
authors.forename: Katsumi
authors.initials: K
authors.lastname: Murakami
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mochizuki
authors.forename: Satoru
authors.initials: S
authors.lastname: Takami
authors.forename: Reiko
authors.initials: R
authors.lastname: Muramatsu
authors.forename: Hiromi
authors.initials: H
authors.lastname: Tadaki
authors.forename: Satomi
authors.initials: S
authors.lastname: Hagiwara
authors.forename: Takahisa
authors.initials: T
authors.lastname: Mizuno
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Arakawa
authors.forename: Yukio
authors.initials: Y
authors.lastname: Nagasaka
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology; D001980:Bronchi / Q000187:drug effects / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction / Q000187:drug effects / Q000502:physiology; D001993:Bronchodilator Agents / Q000494:pharmacology; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage* / Q000494:pharmacology; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D012135:Respiratory Sounds / Q000187:drug effects / Q000503:physiopathology*; D012189:Retrospective Studies; D013147:Spirometry
chemical_list: D001993:Bronchodilator Agents; D016210:Methacholine Chloride