PROBLEMS OF IMPEDANCE CARDIOGRAPHY

It is very difficult to obtain exact information about hemodynamics from the waveforms measured by the impedance cardiograph, in spite of the fact that the waveforms include much useful information. From theoretical and experimental studies, it is concluded that: (a) the waveforms measured by an impedance cardiograph are affected not only by the change of blood volume in the aorta but also by that in various organs such as the heart and lungs; (b) the impedances measured by a pair of small electrodes separated by a short distance give useful information about the region in the vicinity of the electrodes; (c) much valuable information will be available, if the relationships between the measurement results and the pulsatile blood flow are understood, and (d) by choosing an appropriate electrode arrangement, we may get much useful information about the blood circulation in the organs we want to investigate.