Histamine log(dose)-Response Curves in Asthmatics

Abstract

In 9 asthmatic patients log(dose)-response curves were obtained on 4 successive days with the Wiesbadener Doppelinhalator (WDI) and the De Vilbiss (De V) 645 nebulizer, respectively. log(dose)-response was expressed as a quadratic regression equation. From those equations the dose, causing a fall in response (FEV₁) of 10% of the initial value, was obtained and defined as the provocative concentration (PC(10)) or sensitivity. Moreover, the reactivity was defined as the slope of the linear regression through the steeper part of the curve. Although we compared the De V and the WDI log(dose)-response curves after correction for the different liquid output, a significantly greater sensitivity was found for the De V nebulizer. As to the reactivity, no significant differences were found. The difference in sensitivity could perhaps be explained by the fact that, as compared with the De V nebulizer, the WDI may cause a larger deposition of aerosol on the throat and the pharynx, due to the much greater linear velocity of its aerosol jet.