A tissue impedance measurement chip for myocardial ischemia detection

In this paper, the design of a specific integrated circuit for the measurement of tissue impedances is presented. The circuit will be part of a multi-micro-sensor system intended to be used in cardiac surgery for sensing biomedical parameters in living bodies. Myocardium tissue impedance is one of these parameters which allows ischemia detection. The designed chip will be used in a four-electrode based setup where the effect of electrode interfaces are cancelled by design. The chip includes a circuit to generate the stimulus signals (sinusoidal current) and the circuitry to measure the magnitude and phase of the tissue impedance. Several integrated circuits have been designed, fabricated and tested, in a 0.8-μm CMOS process, working at 3 V of power supply. Some of them including building blocks, and other with the whole measurement system. Experimental tests have shown the circuit feasibility giving expected results for both in-vitro and in-vivo test conditions.