[Plasma extravasation in the tracheo-bronchial airways. Mechanisms and physiopathological consequences in asthma]

Plasma extravasation (EP) is an important phenomenon during the course of inflammation. In asthmatic subjects, EP is produced not only in the walls of the airways, but also in the lumen. This has consequences for the bronchial calibre and the qualitative and quantitative characteristics of the secretions. Numerous experimental methods have been developed in animals in order to study EP induced in the airways by different stimuli. For the most part these are inapplicable in man where EP is generally validated in an indirect fashion by measuring the quantity of certain plasma proteins, such as albumin in the secretions or the bronchoalveolar lavage. EP is linked to an increase in the permeability of the vessels, notably this is situated in the subepithelial zone. It is influenced by the appearance of disruption between the endothelial cells and possibly amplified by an increased blood flow linked to vasodilatation. It is the association of these phenomena of epithelial hyperpermeability which favours the appearance of EP in the lumen. In experimental systems the greater part of the mediators implicated in the pathophysiology of asthma are capable of inducing EP in the airways. The perfecting of reliable and non-invasive methods of study is, however, necessary to achieve a perfect understanding of the role of EP in the pathophysiology of asthma or other inflammatory diseases of the bronchi and to assess the efficacy of this parameter of different therapeutic techniques.