Intravital microscopy: Airway circulation

Abstract

Tracheobronchial circulation provides many important physiological functions including delivery of blood-borne nutrients and hormones, removal of waste products, conditioning of inspired air, and maintenance of interstitial fluid volume. Blood flow to the airways must be closely regulated to maintain these critical functions in the face of continually changing metabolic and respiratory demands. Study of the mechanisms which regulate blood flow to the airways is unfortunately problematic due to the complex morphology of this vascular bed. The tracheobronchial circulation receives inputs from the intrathoracic bronchial artery, the inferior and superior thyroid arteries, and anastomoses with the esophageal circulation. Venous blood may leave the airway tissue via the superior and inferior thyroid veins, the intrathoracic bronchial vein, or through bronchopulmonary and esophageal anastomoses. Therefore, it is problematic to isolate and study the airway vasculature by traditional methods that have been applied with great success to other vascular systems, such as the pulmonary, mesenteric, and skeletal muscle circulations.