DISTRIBUTION OF BLOOD-FLOW AND NEUTROPHIL KINETICS IN BRONCHIAL VASCULATURE OF SHEEP

The bronchial circulation, as opposed to the pulmonary circulation, is the Likely source of the edema and inflammatory cells that contribute to airflow obstruction and airway narrowing associated with asthma an d pulmonary edema. The purpose of this study was to understand the mec hanism of edema formation and inflammation in airway walls. Therefore, we sought first to determine the normal bronchial venous drainage pat hways. In anesthetized, ventilated, open-chest sheep we measured the r elative distribution of Cr-51-labeled red blood cells to the right and left ventricles after injection into the bronchial artery (n = 7). Us ing this information, me then studied the kinetics of leukocytes in th e bronchial vascular bed. We measured the extraction of In-111-labeled neutrophils during their first pass through the microvasculature afte r injection into the bronchial artery or right ventricle (n = 6). In t he first set of experiments, we found >85% of the systemic blood flow to the lung returns to the left ventricle. In the second set of experi ments, we found that extraction of neutrophils in the bronchial vascul ature (50-60%) was less (P < 0.05) than that in the pulmonary vasculat ure (80%). This finding may be explained by differences in the anatomy and/or hydrodynamic dispersal forces between the pulmonary and bronch ial vascular beds or may reflect sequestration of neutrophils within t he pulmonary microvasculature while traversing bronchial-to-pulmonary anastomotic pathways.