Portable thoracic bioimpedance monitor design

Impedance cardiography (ICG) is a noninvasive method for monitoring cardiac dynamics using electrical bioempedance (EBI) measurements. Physiological impedance cardiography measures hemodynamic parameters without the risks associated with conventional interventional methods. There are studies based on the use of ICG in various cardiovascular diseases such as circulatory system diseases, acute and chronic heart failure, acute myocardial infarction, hypertension, severe anemia, and pacemaker patients. Analysis of ICG waveform continuously used at a single frequency; Cardiac output (CO), stroke volume (SV), systolic time intervals and monitoring of oxygen supply and consumption balance are used to evaluate some hemodynamic parameters showing the mechanical function of the heart. To determine the level of resistance change in the thoracic fluid when performing an ICG measurement, two electrodes emit a low amplitude electric current across the thorax region and detect two different electrode voltage changes. Impedance is obtained by using Ohm's law. Changes in blood from the breast, heart and other major vessels with the measured impedance are recorded as ΔΖ. ICG recording also generates the dZ / dt waveform obtained from the first derivative of the ∆Z signal. ICG waveforms, along with the recorded ECG, are used to calculate and evaluate hemodynamic parameters. In this study, a portable, inexpensive, small size, modular and digital bioimpedance measurement system has been designed for the examination of hemodynamic parameters. Thanks to the designed system, it was aimed to find solutions to various problems such as increasing the quality of life of home care patients, closing the shortage of health personnel and reducing health expenditures. In this study, a four electrode ICG prototype was designed and constructed using an ADAS1000 evaluation kit. Thoracic impedance at 50 kHz frequency and ECG measurements were taken with the designed prototype. With the developed software, ICG signal is generated from thoracic impedance values and inferences about hemodynamic parameters are made. The results show that the measured thoracic impedance value is higher than the reference values, but the impedance change is within the reference values. It is concluded that the prototype is not suitable for clinical use and needs to be improved.