Comparison of histamine bronchial challenges with the Wright nebulizer and the dosimeter

Abstract

In 20 adult asthmatics studied in a stable state, histamine bronchial challenges were carried out at 1 wk intervals with the Wright nebulizer and with the dosimeter-DeVilbiss apparatus. Dose-response curves were analyzed for sensitivity, defined as the minimal histamine dose causing a 20% fall in FEV1 [forced expiratory volume at 1 s] (PC20 [provocative concentration]) and for reactivity, defined as the slope of the dose-response curve once the reaction starts to occur. A significant relationship (r [correlation coefficient] = 0.80) was found for sensitivity obtained with the 2 nebulizers. PC20 was indeed reproducible within a 2 folds concentration of histamine in 16 of the 20 patients. A significant difference (P < 0.01) was found in the reactivity to the 2 different apparatus, reactivity being greater with the Wright nebulizer in 12 of 15 patients so tested. Sensitivity and reactivity showed a borderline relationship (r = 0.47) with the Wright nebulizer but not with the dosimeter. A significant correlation (P < 0.05) existed between the initial FEV1 (in % of the predicted value) and the observed sensitivity and reactivity as assessed with the Wright nebulizer, but not as assessed with the dosimeter. Histamine bronchial challenges with the Wright nebulizer and with the dosimeter yield reproducible results if the threshold of a 20% fall in FEV1 is taken as positive. The 2 methods produce different results in terms of reactivity.