Effect of Maximal Respiratory Manoeuvres on Bronchial Sensitivity of Asthmatic Patients as Compared to Normal People

Abstract

Cumulative dose-response curves to carbachol given by aerosol were established using plethysmographic measurements of specific airways resistance (SRaw) in 10 patients with asthma and five healthy subjects. Two experiments were performed—a control test and one in which maximal respiratory manoeuvres (MRM) (two maximal inspirations and two maximal expirations) were made before each carbachol inhalation. MRM did not modify the dose-response curves in the normal subjects. In the patients these manoeuvres enhanced the bronchoconstrictor effect of carbachol: curves were shifted to the left and the mean dose of carbachol producing a twofold increase in initial SRaw was decreased. from 0.373 mg to 0.189 mg (P <0.001). Bronchial provocation tests using methods which require MRM—for example, forced expiratory volume at one second—could overestimate the bronchial sensitivity of patients with asthma. © 1975, British Medical Journal Publishing Group. All rights reserved.