Although the change in the conductance of blood resulting from changes in its velocity has been noted by several investigators working with electrical impedance techniques, this parameter of measurement has heretofore not been investigated from the viewpoint of practical application to blood flow measurement.

In certain regions of the body such as the tooth pulp and the cranial cavity, the volume of the contained blood cannot fluctuate during a cardiac cycle because of the rigid wall of the chamber. Therefore, impedance pulses which have been obtained in studies on the tooth pulp, must be attributed to the rhythmical fluctuation of the conductance of the blood resulting from changes in its velocity.

The scope of this paper is concerned with a theoretical analysis of several factors accounting for the above phenomenon and comparison of the theoretical results with experimental data obtained for different types of circulatory models.