Carbonic Anhydrase Inhibitors as Broncholytic Substances

Abstract

Broncholytic substances decrease the bronchial tone and therefore the anatomical dead space volume (VD). This was shown in case of atropine by Severinghaus and Stupfel (J.Appl.Physiol. 8, 81, 1955). The method of Fowler was used. We have developed a new method for measuring the anatomical dead space, which is also applicable in case of lung desease (Barnikol, Diether: Pneumonologie 152, 227, 1975; Barnikol, Diether, in preparation). The anatomical dead space volume can be measured breath by breath. With the new method first the bronchial actions and reactions in time and second by variation of tidal volume (VT) the VD-VT-relation can be measured. The slope of this relation is a measure for the bronchial compliance. Application of fenoterol to lung healthy people results in an increase of both, anatomical dead space (30 ml) and bronchial compliance. With the aid of our new method we have reinvestigated the influence of CO₂ on the bronchial system. In literature there are discrepancies (Stein et al., Resp. Physiol. 25, 363, 1975; Widdicombe, Physiol.Rev. 43, 1, 1963; Barer et al., Bull.Physiol.Path. 8, 459, 1972). Some authors find bronchodilation, others bronchoconstriction after application of CO₂.