BRONCHIAL REACTIVITY TO CIGARETTE-SMOKE IN SMOKERS - REPEATABILITY, RELATIONSHIP TO METHACHOLINE REACTIVITY, SMOKING AND ATOPY

Bronchial reactivity to cigarette smoke (CBR) in a cross-section of 98 smokers has been investigated. All participants were subjects to skin -prick tests to common allergens, lung function measurements and bronc hial challenges with methacholine and cigarette smoke. In 38 participa nts a rechallenge with cigarettes was performed 1 h after the first ci garette challenge. Lung function indices analysed were: forced expirat ory volume in one second (FEV1); maximal expiratory flow at 75% of the forced vital capacity (MEF75%); and forced mid-expiratory flow betwee n 25 and 75% of the forced vital capacity (FEF25-75%). All participant s were tested for asthma and allergy, and were required to provide inf ormation regarding respiratory symptoms, first degree relatives with a sthma and allergy and smoking habits. A substantial decrease was seen in all lung function indices after 12 cigarette-smoke inhalations, but only FEV1 was related to other variables. The maximal mean percentage fall in FEV1 was 10%, which was directly related to the number of inh alations (p<0.05). In multiple regression analyses the percentage fall in FEV1 was directly related to: FEV1/vital capacity (VC) (p<0.01); t o the asthmatic/bronchitic status (p<0.05); and to the accumulated and standardized cigarette consumption (p<0.05). The percentage fall in F EV1 bore no relationship to methacholine bronchial reactivity, sex or age and had a continuous distribution. The repeat challenge showed a s maller fall in FEV1 compared to the first challenge after 12 cigarette smoke inhalations (p<0.05). The percentage fall in FEV1 correlated af ter the first and the repeat challenge (p<0.05). Repeatability of the challenge could not be determined in this study because of tachyphylax is. Bronchial reactivity to cigarette smoke is a tobacco smoke-specifi c bronchial response. All participants responded and the response show ed a continuous distribution. Bronchial reactivity to cigarette smoke may be of importance for symptoms and prognosis in chronic bronchitis and chronic obstructive pulmonary disease and should be studied in rel ation to the degree of accelerated lung function loss in smokers and o ther cigarette induced lung abnormalities.