| Abstract |
The bronchial responsiveness characteristics in a cohort of normal Greek population was investigated by the opening interrupter total resistance to breathing technique (Rt). We studied one hundred and seventy normal subjects, 100 male and 70 female (aged 38±8.5 and 35±7.5 respectively), non-smoking from normal families, ranging 18-60 years of age. 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 resistance by 100% (PD100Rt) as well as by the dose response ratio (DRR). Rt was calculated from the pressure change at the end of the interruption period (end interruption Rt). Bronchial hyperresponsiveness (BHR) at a cut-off level of 0.8 mg methacholine exhibited 31 (18%, specificity 82%) normal subjects, 21 males and 10 females, while 3% of the total showed a response in the asthmatic range. No correlation were found between threshold dose or DRR and baseline airway calibre. Age and sex did not appear to influence the results. The method was well reproducible and showed good correlation with PD20FEV1 (r=0.76), with relatively narrow limits of agreement at -1.39imol and 1.27imol methacholine respectively. Rt-DRR was statistically far more sensitive than FEV1-DRR in assessing the bronchoconstrictor responses, especially in subjects with abnormal reactions. Thirty eight percent of the subjects showed a plateau effect while their Rt-DRR was statistically 2.5 times less to the rest of the subjects with normal reactions. We conclude that the interrupter methodology is clinically useful and may represent an alternative to FEV1 in situations when forced expirations cannot be performed. Since asymptomatic bronchial hyperresponsiveness is not a rare occurrence, further prospective studies are required in order to assess the epidemiological details of such a condition.
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Η βρογχική πρόκληση μεταχολίνης σε φυσιολογικό Ελληνικό πληθυσμό
