Changes in the dimensions of the venae cavae

¹ Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington

In 11 dogs a variable resistance gauge, a bonded strain gauge, or mutual inductance coils were installed on the venae cavae under aseptic surgical conditions so that dimensional changes in unexposed veins could be measured directly. The cyclic patterns of dimensional change resembled inverted images of venous flow records obtained by others. Since some changes in the venous dimensions apparently were not related to pressure, active contraction of the walls may have been responsible. Studies involving infusion and hemorrhage confirmed the existence of two phases in the pressure-diameter relationship correlated with the level of venous pressure. The pattern of diameter and venous pressure changes during transfusion and withdrawal of blood tended to be a clockwise hysteresis loop.

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