Illustration showing the use of a Ventolin inhaler to control recurrent attacks of asthma, featuring a cutaway drawing of a man which shows the tree" of branching airways in both lungs. A cross- section through a division of a bronchus is shown in detail at bottom right. A Ventolin inhaler contains the drug salbutamol, which dilates the bronchial muscles allowing air to pass to the lungs. In bronchial asthma a narrowing of the airways is produced by spasm of the muscles in the bronchial tubes. These spasms are associated with swelling of the lining surfaces accompanied by an increased in mucous secretion."