Direct measurement of bronchial arterial flow.

THE normal bronchial arterial blood flow provides only a very small portion of the blood flow through the lungs.' 2 Since it supplies oxygen and nutrients to the bronchial musculature and mucosa, it may have importance for pulmonary mechanisms far beyond that expected on the basis of its small flow. After giving up its oxygen on passage through the pulmonary parenchyma, this flow passes into the pulmonary system where it may contribute oxygen-depleted blood to the pulmonary venous outflow. Precapillary anastomoses probably play a minimal role under normal circumstances.' Because of the great potential for proliferation of the bronchial vascular system in congenital anomalies and inflammatory conditions, and after experimental obstruction of the pulmonary artery,' ° the flow through this system may also have relevance in the evaluation of circulatory mechanisms. The normal anatomy of the nutrient arteries supplying the parenchyma of the lung was studied long ago by Leonardo da Vinci, von Haller, and Kiittner. The great variability in the topographical origin was early recognized. Cockett and Vass have reviewed the pertinent literature. Kiittner demonstrated that dye injections into the aorta resulted in the staining of the bronchial mucosa in man; he described the posterior bronchial arteries in the dog and showed that the branches to the right and left lung often had a common trunk with a medial intercostal artery, emerging from the aorta at the sixth thoracic segment. Berry et al. confirmed the arrangement desci'ibed by Kiittner. Notkovich, in an extensive study