Thoracic Simulator for Impedance Cardiography

Abstract – Impedance cardiography is a non-invasive technique for measuring cardiac output and for diagnosing cardiac disorders. During systol, blood is pumped into the thoracic region which changes its basal impedance. High frequency (20–100 kHz) current (3–10 mA) is injected into the thoracic region through a pair of electrodes and the impedance change is sensed, by measuring the voltage across another pair of electrodes. The impedance variation thus measured is known as impedance cardiogram (ICG) and can be used for estimating stroke volume by using appropriate models of blood flow and can also be used for diagnostic information. As part of instrumentation development, a thoracic impedance simulator has been developed for comprehensive testing and calibration of the impedance cardiograph instrument to ensure proper signal pickup and detection of impedance variation. Features of this simulator include the variation of base impedance of the thorax by less than 1 percent as a square wave, electrode– tissue contact impedances for 4 – electrode configuration, 24 – 300 beats/min heart beat rate, 0 – 60 mV common mode ECG, 0 – 20 mV differential ECG, and option for feeding external pickup