Portable Impedance Cardiography System for Real-Time Noninvasive Cardiac Output Measurement

Impedance cardiography (ICG) is the only known method that can observe the continuous left ventricular volume changes non-invasively and conveniently. This paper proposes to develop a portable ICG system for long-term continuous cardiac activity monitoring using the impedance technique. This ICG system combines the advance analog amplifier with the calculation power of digital signal processing chip to achieve real-time monitoring. One of the major differences between the proposed system and the existing systems is in the bandwidth of dZ/dt circuit. Using proper bandwidth can significantly increase the reliability and validity of ICG signal. Additionally, the proposed system is light weight and suitable for a portable monitoring system.The results demonstrate that the proposed ICG system is capable of tracking the dynamic changes of SV and CO during physiological challenges such as Valsava maneuver and the hand grip task. On the other hand, the results also show that there is no difference between CO obtained by the proposed ICG system and the Fick method. Additionally, the correlation coefficient is 0.91. The results indicate that the proposed system is a valid and reliable tool for patient monitoring and it is capable of assessing the dynamic cardiac activity information.Due to the simplicities of the current signal processing and events detection methods, the CPU is idled for substantial amount of time. Thus, in the future, more advanced techniques such as adaptive filtering and wavelet analysis can be implemented for event detection to increase the accuracy and reliability.