[Standardization of the carbachol inhalation provocation tests using a reservoir method]

Abstract

Provocation tests with pharmacodynamic substances should preferably be conducted as dose-effect relation tests. Reservoir methods are well suited to guarantee a relatively constant intrabronchial deposition in respect of both the site of deposition (centrally, peripherally) and the deposited quantity. A commercially produced reservoir method has been available for some time now (Provocation test IR, Pari-Medanz, Starnberg). It was the aim of our study to find out which initial concentration of carbachol is necessary with this reservoir method to avoid incidents even if there is a marked hyperreactivity. Another goal was to find out the cumulative total quantity allowing differentiation between healthy subjects and asthmatic patients (cumulative total dose; maximum possible sensitivity and specificity). In 22 patients assessed to have healthy lungs according to clinical criteria and 22 subjects suffering from clinically confirmed asthma bronchiale, provocation tests were performed using increasing quantities of carbachol: Carbachol concentrations of 0.05%, 0.1%, 0.2%, 0.4% and 1.0% were nebulized to a aerosol volume of 5 litres. Whole body plethysmography was performed after each carbachol inhalation (Raw, FEV1, ITGV), so that dose-effect relations could be established. To calculate bronchial hyperreactivity, straight lines of linear regression were calculated for Raw (y = mx) (calculation of reactivity after Orehec). From this we calculated average reactivities for healthy subjects and asthmatic patients with pertaining standard deviations. We found that an initial dose of 0.05% carbachol sprayed in an aqueous solution in relation to 5 litres, was unnecessary if the patients did not suffer from any relevant obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)