Signal processing of bioimpedance equipment

Measurement of the electrical impedance of tissue is used as a non-invasive method especially in diagnostics of the cardiovascular system. Impedance changes in the tissue are influenced by blood flow in this tissue. The changes provide hemodynamic information. When scanning bioimpedance signals on the periphery of the body, it is necessary to construct the bioimpedance measuring equipment in such a way that maximum sensitivity of the arrangement is achieved by maximum suppression of interfering signals and noise. An adaptive digital filter, optimised on the basis of an analysis of the bioimpedance signal, achieves a marked decrease in the interference level and noise, and increases its diagnostic value. It extends the application range of the bioimpedance method for tracing the hemodynamics not only of the heart and major arteries but also of tissues and organs. (C) 2003 Elsevier B.V. All rights reserved.