Bronchial blood flow and microvascular permeability in the pathophysiology of asthma.

Bronchial smooth muscle contraction is not the only causative factor of airway narrowing in asthma. Other components, such as mucosal and submucosal oedema and mucosal inflammation, also intervene in the processes leading to bronchial obstruction. Re-analyzing the role of the tracheo-bronchial circulation is therefore necessary, since participation of the latter, through modification of bronchial blood flow and/or alteration of microvascular permeability, very likely modifies mucosal thickness of the bronchial wall and/or clearance of bronchoactive substances from the airways. This also implies that more attention should be paid on the vascular actions of compounds which are either currently prescribed or under development for future treatment of asthma.