Abstract

Eight patients with exercise-induced asthma participated in a single-blind trial comparing the protective effects of inhaled lignocaine (estimated dose 48 mg), sodium cromoglycate (estimated dose 12 mg), and ipratropium bromide (estimated dose 120 μg). Saline was used as control. Effects were assessed from the mean maximal percentage fall in forced expiratory volume in one second (FEV₁) and maximal mid-expiratory flow rates (MMFR) after they had run on a treadmill for eight minutes. There was no significant change in baseline FEV₁ or MMFR before each agent was given. Saline, lignocaine, and sodium cromoglycate did not alter the mean baseline FEV₁ or MMFR significantly. Ipratropium caused bronchodilatation with an increase of 16·3% in the mean FEV₁ (p<0·001) and of 43·4% in the mean MMFR (p<0·05). After exercise the maximal percentage falls in FEV₁ (means and SEM) after saline, lignocaine, sodium cromoglycate, and ipratropium bromide were 38·1% (5·0), 34·5% (6·1), 11·3% (3·7), and 19·3% (7·4) respectively. Similarly, the mean maximal falls in MMFR after saline, lignocaine, sodium cromoglycate, and ipratropium bromide were 54·4% (5·2), 52·9% (7·7), 23·6% (6·6), and 32·1% (10·5) respectively. The inhibitory effects of sodium cromoglycate and ipratropium bromide were significant whereas lignocaine failed to produce an effect. These results suggest that mediator release is an important factor in exercise-induced asthma and that in some patients the effects of the mediators may be on the postsynaptic muscarinic receptors. Local anaesthesia of sensory vagal receptors, on the other hand, does not prevent exercise asthma and these receptors do not appear to have any important role in exercise-induced bronchoconstriction.