Analysis of Diameter and Flow Velocity Changes in Small Pulmonary Vessels During Regional Alveolar Hypercapnia

Abstract

Effects of alveolar hypercapnia on the pulmonary vessels have been studied chiefly by measuring the pressure-flow relationship [1–3]. Some of the results have suggested an increase in the vascular resistance to blood flow in the hypercapnic lung area [1, 2], whereas others have not [3]. However, we consider that for detecting the local pulmonary vasomotion during alveolar hypercapnia, it is necessary to measure directly the internal diameter (ID) of small pulmonary vessels with rich smooth muscle layers. In this study, using a new X-ray TV system developed in our laboratory [4], we quantitatively analyzed the changes in 10 of the small pulmonary arteries and veins (100–600 μm 10) in unilobar alveolar hypercapnia. Simultaneously, flow velocity and volume flow in the small arteries were analyzed.