Static and dynamic pressure-volume relations of the veins in the cat hind leg (author's transl)

Abstract

In the artificially perfused hind legs of cats in vivo (chloralose anaesthesia) the distensibility characteristics of veins were investigated under conditions of different modes of pressure changes along the venous system. A dynamic pressure-volume relationship was obtained by a continuous change of venous outflow pressure. A static pressure-volume relationship was obtained by incremental variation of hydrostatic venous inflow or outflow pressure, respectively. Venous inflow pressure was varied by alteration of blood flow. Venous outflow pressure was changed by raising the level of the outflow orifice of the venous circuit. The static pressure-volume curve which occured with venous outflow elevation showed a sigmoid shape. The compliance was greatest at a pressure range of 8 to 28 mm Hg. It was smaller at the lower and higher pressure. The reduction in venous compliance was due to collaps phenomena and resistance changes or a decrease in vascular elasticity, respectively. The volume changes which occured with elevation of blood flow were greatest at the lower flow values. Dynamic changes of venous outflow pressure resulted in hysteresis loops. The width of the loop depended on vascular viscosity, venous resistance and transcapillary fluid transfer. On the contrary, nearly the whole area between the ascending limb of the dynamic and the static pressure volume curves was due to the viscosity.