title: Development of wheezing in patients with cough variant asthma during an increase in airway responsiveness.
abstract: Two theories explaining the mechanism for the manifestation of cough without wheeze in patients with cough variant asthma (CVA) are either a higher wheezing threshold or a milder degree of airway hyperresponsiveness. A significant proportion of patients diagnosed as having CVA eventually develop wheezing. The aim of this study was to investigate whether this change in the manifestation of asthma was associated with a decrease in wheezing threshold and/or an increase in airway hyperresponsiveness. Thirty-six children (7-15 yrs) with CVA were prospectively studied for 4 yrs. Bronchial provocation tests with methacholine using the stepwise increasing concentration technique were performed annually to measure the provocative cumulative dose producing a 20% fall in forced expiratory volume in one second (PD20). Wheezing thresholds were additionally determined at the initiation of and the end of the study (development of wheezing, or after 4 yrs). Sixteen (Group 1) of 29 patients available for the follow-up developed clinical wheezing during the period; 13 patients (Group 2) stayed as CVA or their cough resolved. There was no significant change in wheezing thresholds from the initiation to the end of the study (Group 1: 40.9+/-8.2% versus 40.2+/-8.3%; Group 2: 41.4+/-7.1% versus 40.1+/-7.3%). Methacholine PD20 (geometric mean, range of 1 SD), expressed as breath unit (BU), significantly decreased in Group 1 patients as they developed wheezing (initial versus wheezing year: 60.8 BU, 29.2-126.5 versus 32.8 BU, 11.5-93.3; p<0.01), whereas the value did not change in Group 2 patients (initial versus after 4 yrs: 85.3 BU, 45.2-161.1 versus 84.3 BU, 39.7-179.1; NS). The results suggest that an increase in airway hyperresponsiveness, but not a decrease in wheezing threshold, may have a pathogenetic role in the development of wheezing during the course of cough variant asthma in childhood.
authors.affiliation: Dept of Pediatrics, Seoul National University College of Medicine, Korea.
authors.forename: Y Y
authors.initials: YY
authors.lastname: Koh
authors.forename: J H
authors.initials: JH
authors.lastname: Jeong
authors.forename: Y
authors.initials: Y
authors.lastname: Park
authors.forename: C K
authors.initials: CK
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000403:Airway Resistance / Q000502:physiology; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D002648:Child; D003371:Cough / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D011446:Prospective Studies; D012135:Respiratory Sounds / Q000503:physiopathology*
chemical_list: D016210:Methacholine Chloride