Chronic bronchitis: reflex on the pulmonary circulation.

Chronic obstructive pulmonary disease (COPD) is characterized by lower alveolar oxygen content and hypoxia. Hypoxia itself is able to evoke a vascular reflex in a pulmonary vasoconstriction, the explanation of which is, in part, unknown. Pulmonary vasoconstriction leads to different degrees of pulmonary artery pressure (PAP) increase which statistically suggests that the higher the PAP, the poorer the survival rate. Many substances are involved in the vascular homeostasis. An important role is played by cyclooxygenase as well as lipoxygenase pathways metabolites, the antagonists of which have been extensively used in the treatment of pulmonary hypertension in subjects suffering from COPD. An even more important role is played by the endothelium. It is able to modify its metabolism towards the production of substances (e.g., endothelin, EDRF, etc.) which are able to negatively influence the vascular tone. Complete identification of such substances, when possible, would allow us to have a better understanding of the complexity of the mechanism which controls the pulmonary vascular district. In this direction we could hopefully look forward to the detection of specific new drugs able to improve the management of the disease by preventing it from worsening to that extent which statistically and drastically correlates with the worst prognosis.