Abstract
BackgroundA 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.MethodsWe 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).ResultsBHR 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 μmol and 1.27 μmol methacholine, respectively, but the interrupter methodology proved more sensitive than FEV1 in terms of reactivity (DRR).ConclusionsInterrupter methodology is clinically useful and may be used to evaluate bronchial responsiveness in normal subjects and in situations when forced expirations cannot be performed.
Highlights
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)
In this study we have shown that the interrupter technique, and PD100Rint, Interrupter Resistance at End Interruption (EI), is comparable to the conventional PD20FEV1 method for evaluation of BHR in a large sample of normal subjects
The Rint, EI was measured during expiration above forced residual capacity (FRC), because resistance hardly changes above this level and since subjects performed relaxed tidal flow maoeuvres, measurements were not affected by variations in breathing
Summary
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. The interrupter method has been shown to be a simple and non-invasive technique of measuring airway mechanics in children or patients with limited co-operation [4]. It is suitable for diagnostic purposes in the detection and exclusion of asthma [5] and in obtaining valid rhinomanometric measurements in various groups of patients [6]
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