A RAPID DOSIMETRIC METHOD WITH CONTROLLED TIDAL BREATHING FOR HISTAMINE CHALLENGE - REPEATABILITY AND DISTRIBUTION OF BRONCHIAL REACTIVITY IN A CLINICAL MATERIAL

A rapid dosimetric method with controlled tidal breathing for histamine challenge was evaluated by assessment of its repeatability, by comparing to a present nondosimetric standard method, and by application to adult patients with recent asthma (n=31), chronic asthma (n=33), chronic cough (n=71) or chronic rhinitis (n=41) and to healthy controls (n=31). An automatic inhalation-synchronized dosimetric jet nebulizer with a known lung deposition of the aerosol was used to administer histamine and to control breathing. The non-cumulative doses of histamine diphosphate were 0.025, 0.1, 0.4 and 1.6 mg, administered during 0.4 s following tidal inspiration of 100 ml of air. The test procedure required 1 inhalation of histamine 4 mg/ml and followed by 1, 4 and 16 inhalations of histamine 16 mg/ml from the device, and its duration was about 30 minutes. The intraindividual correlation coefficient of the histamine dose causing a reduction of 15 percent in FEV1 (PD15FEV1) on 2 consecutive days in 14 asthmatic subjects was 0.937; the standard error of the single determination was 13 Percent of the mean PD15FEV1. A PD15FEV1 value below 0.4 mg was found only in asthmatic subjects; in chronic asthma, below 0.5 mg; in recent asthma, between 0.1 mg and 1.6 mg or more. In patients with chronic cough and chronic rhinitis, 20 and 32 percent, respectively, the PD15FEV1 values between 0.4 and 1.6 mg, the other patients in these groups were non-responsive. In all healthy control subjects, the PD15FEV1 was over 1.0 mg, 80 percent of them were nonresponsive to the maximum 1.6 mg dose. This new test allows rapid, accurate, and quantitative assessment of bronchial responsiveness to histamine.