Tissue pressure and critical closing pressure in the isolated denervated dog foreleg

¹ Departments of Physiology and Surgery, University of Minnesota Medical School, Minneapolis, Minnesota

Experiments designed to obtain very low pressures and flows in the isolated leg were performed on the weighed, denervated dog foreleg perfused with homologous blood. Continuous strain gauge recordings of pressure decay curves and rates of weight loss (venous outflow) were obtained after arrest of the arterial inflow. In some instances tissue pressures were measured by a ‘null-point’ procedure. The results provide no evidence for a generalized critical closing pressure in the denervated, blood-perfused, nonedematous leg. After occlusion of arterial inflow the arteriovenous pressure difference fell to zero (0.0 mm Hg) as venous outflow approached zero. Evidence was obtained showing that if a pressure difference is found at zero flow in the isolated leg, it is produced by the existing tissue pressure. An elevated closing pressure is readily obtained in the dog foreleg when the tissue pressure is increased, and its magnitude is directly related to the extent of tissue edema.