Pulse Wave Modeling using Bio-Impedance Simulation Platform based on a 3D Time-Varying Circuit Model.

Cardiovascular disease (CVD) threatens the lives of many and affects their productivity. CVD is diagnosed through hemodynamic parameters that vary significantly throughout the day. Wearable sensors can enable continuous monitoring of hemodynamic parameters to improve the diagnosis and management of CVD. Bio-Impedance (Bio-Z) is an effective non-invasive sensor for arterial pulse wave monitoring based on blood volume changes in the artery due to the deep penetration of its current signal inside the tissue. However, the measured data are significantly affected by the placement of electrodes relative to the artery and the electrode configuration. In this work, we created a Bio-Z simulation platform that models the tissue, arterial pulse wave, and Bio-Z sensing configuration using a 3D circuit model based on a time-varying impedance grid. This circuit model is simulated in SPICE and can be used to guide design decisions (i.e. electrode placement relative to the artery and electrode configuration) to optimize the monitoring of pulse wave prior to experimentation. We present extensive simulations of the arterial pulse waveform for different sensor locations, electrode sizes, current injection frequencies, and artery depths. The simulations are validated by in vitro Bio-Z measurements. This model will enable researchers and designers to create time-varying blood flow models and rapidly test the effectiveness of the sensing methods and algorithms without the need for extensive experimentation.