Axial and radial distribution of the bronchial vasculature in sheep

A morphometric analysis was made on the bronchial vasculature of intrapulmonary airways in sheep lungs. This study provides the parameters to calculate the quantity of soluble gas diffusion between the vasculature and airways for use in a mathematical model describing heat and mass exchange in the lungs. To achieve these results, the lungs of four adult sheep (30-36 kg.) were excised, fixed, dissected and microtomed to obtain airway cross-sections for measurement. Blood vessel size and airway proximity was measured using a microscope interfaced with a computer. Distance from airway lumen to most airway vessels ranged from 30 to 270 microm. It was found that the bronchial vessels surrounding intraparenchymal airways can be described by a right-skewed distribution. Most importantly, a practical description of the bronchial capillary size and airway proximity as a function of airway diameter was found using a weighed average. This analysis facilitates calculation of soluble gas flux from the bronchial vasculature to the airway for use in a mathematical model.