title: Use of interrupter technique in assessment of bronchial responsiveness in normal subjects.
abstract: BACKGROUND
  A number of subjects, especially the very young and the elderly, are unable to cooperate and to perform forced expiratory manoeuvres in the evaluation of bronchial hyperresponsiveness (BHR). The objective of our study was to investigate the use of the interrupter technique as a method to measure the response to provocation and to compare it with the conventional PD20 FEV1.
  
  
  METHODS
  We studied 170 normal subjects, 100 male and 70 female (mean +/- SD age, 38 +/- 8.5 and 35 +/- 7.5 years, respectively), non-smoking from healthy families. These subjects had no respiratory symptoms, rhinitis or atopic history. A dosimetric cumulative inhalation of methacholine was used and the response was measured by the dose which increases baseline end interruption resistance by 100% (PD100Rint, EI) as well as by percent dose response ratio (DRR).
  
  
  RESULTS
  BHR at a cut-off level of 0.8 mg methacholine exhibited 31 (18%) of the subjects (specificity 81.2%), 21 male and 10 female, while 3% showed a response in the asthmatic range. The method was reproducible and showed good correlation with PD20FEV1 (r = 0.76, p < 0.005), with relatively narrow limits of agreement at -1.39 mumol and 1.27 mumol methacholine, respectively, but the interrupter methodology proved more sensitive than FEV1 in terms of reactivity (DRR).
  
  
  CONCLUSIONS
  Interrupter methodology is clinically useful and may be used to evaluate bronchial responsiveness in normal subjects and in situations when forced expirations cannot be performed.
authors.affiliation: Department of Pneumonology, Army General Hospital, Athens, Greece. pbpanagou@yahoo.gr
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Panagou
authors.forename: Ioannis
authors.initials: I
authors.lastname: Kottakis
authors.forename: Argyris
authors.initials: A
authors.lastname: Tzouvelekis
authors.forename: Stavros
authors.initials: S
authors.lastname: Anevlavis
authors.forename: Demosthenes
authors.initials: D
authors.lastname: Bouros