The single exposure method for inhalation challenge with allergen

Abstract

We carried out inhalation challenge with a single exposure to a high concentration of allergen (the single exposure method) on 92 asthmatic patients. With the use of the 3 Hz forced oscillation technique, we could continuously and graphically estimate total respiratory resistance (Rrs) throughout the test. The subjects inhaled aerosolized house dust allergen (1 :5 w/v) for 1 min during tidal breathing. As soon as Rrs reached twice that of baseline value or after 10 min from the start of allergen exposure, subjects inhaled aerosolized bronchodilator for 3 min. To evaluate the Rrs response curve to inhaled allergen, we defined provocation time (PT 35-Grs) as the time from the start of allergen exposure to the point at which total respiratory conductance (Grs) decreased 35% from its baseline value and appearance time (Ta) as the time from the start of allergen exposure to the beginning of an increase in Rrs. We presume that Ta may reflect bronchial sensitivity to allergen, since Ta significantly correlated with a unit of allergen causing a decrease in FEVI of 30% (r = 0.66; p < 0.05) in the dosimeter method. We demonstrated that the single exposure method is comparable to the dosimeter method in evaluating bronchial responses to inhaled allergen and also demonstrated the reproducibility of bronchial response to inhaled allergen with the single exposure method.