Partial flow-volume curves to measure bronchodilator dos-response curves in normal humans

Abstract

The use of partial expiratory flow-volume (PEFV) curves to obtain dose-response curves to an inhaled .beta.2-adrenoceptor agonist (salbutamol) was examined in 8 normal subjects. Maximum expiratory flow at low lung volumes increased on PEFV and full expiratory flow-volume curves but the increase was always considerably greater on PEFV (28.4%) than on full (14.5%) curves. The percent increase in flow on the PEFV curve was not significantly influenced by the preceding volume history being 90-120 s of tidal breathing, forced expiration to residual volume or breath holding after a full inflation. Apparently, normal tone during tidal breathing is temporarily reduced, but not abolished, by a full inflation and once basal tone is restored, it is not enhanced by a full expiration. In 7 of the 8 subjects a satisfactory cumulative dose-response curve to inhaled salbutamol was obtained with a plateau value of maximum flow at a dose of 110 .mu.g. The relatively good reproducibility of PEFV curves and the considerable bronchodilator signal obtained (29-70% increase in flow above baseline in different individuals) suggest that such dose-response curves may be useful in studying normal bronchial pharmacology in vivo.