[Normal reactivity and hyperreactivity in the bronchi induced by respiratory irritants]

The influence of age, sex, atopy, baseline spirometry and smoking habit on the presentation of airway reactivity (AR), and the prevalence of hyperreactive subjects was assessed in 176 normals and 143 subjects occupationally exposed to respiratory irritants. The study protocol comprised: a respiratory disease questionnaire, physical examination, skin prick-test to 13 common inhalant allergens, IgE level, spirometry. The nonspecific bronchoprovocation test (NBPT) was performed by the cumulative method proposed by Chai et al. (J Allergy Clin Immunol 1975; 56: 323-327). The results are expressed as PC20FEV1, PC25FEF50, PC25FEF25 and PC25FEF25/75. Age, sex, atopy, baseline spirometric values and smoking are not significantly correlated with indeces of AR. There are no hyperreactors among healthy subjects--according to the criterion: PC20FEV1 less than or equal to 2.17 micromoles of histamine. When the response was measured by flow-volume parameters, there were between 5.1% and 9% hyperreactors. In both examined groups AR has proved to be a highly variable feature. Among workers exposed to irritants there were 5.6% hyperreactors according to PC20FEV1 and between 11.1% and 13.9% when flow-volume parameters were applied. A significant correlation between AR and smoking habit of subjects occupationally exposed to irritants was not found. The level of AR when monitored by flow-volume parameters of subjects continuously exposed to irritants was found to be significantly lower than in normals. The chosen criterion separates successfully airway normo- from hyperreactives. It is a useful diagnostic method in occupational medicine.