[Measuring electrical impedance of organs--instrumental equipment for research and clinical use]

An apparatus for measuring the impedance of intact biological organs or parts of organs in the frequency range of 10 Hz to 10 MHz is described. In this range impedance exhibits a large dispersion, which is dependent on tissue structures. The time course of alterations of electrical impedance such as occur during ischemia can be recorded with this equipment. Five specimens in five measuring chambers can be examined simultaneously at different temperatures. In the second part of the article, a portable impedance meter for measuring the modulus of impedance near 200 Hz, the phase of impedance at 5 kHz and the local temperature at the measuring point, is described. These parameters permit an intra-operative evaluation of the changing state of ischemic organs. Sterilizable probes with four surface electrodes and an integrated temperature sensor permit atraumatic measurements at the organ surface. The measurement itself is harmless to the tissue.