Inhalation occurred for 2 min during quiet breathing through the mouth at 5-min intervals. An isotonic 0.9 percent saline solution was inhaled first, followed by escalating concentrations of histamine from 20 to 10,000 p-g/ml in twofold increments. The FEV, was measured before saline solution inhalation and after each histamine inhalation. The test was continued until the FEV, had fallen by 20 percent or until the highest concentration of histamine had l>een administered. The threshold was defined as the lowest concentration of histamine which resulted in a 20 percent fall of the FEV,. Histamine PC*, was calculated by linear interpolation between the last two data points on the dose-response curve, or was expressed as 15,000 |i.g/ml if there had been no response. Prior to the histamine inhalation test, all drugs were withheld for 24 hours. In order to avoid possible daily changes in response to histamine, the test was performed between 9 and 12 am. buy ventolin inhalers
All patients were initially treated with beta-stiniulants and/or xanthine-derivatives. When asthmatic symptoms were well-controlled, antiallergic agents were administered in addition to beta-stimulants and/or xanthines. Patients were evaluated for bronchial hypersensitivity at least two months after initiation of antiallergic agents (mean periods = 5.7 months).
Tags: Asthma, bronchial hypersensitivity, histamine inhalation