INTRODUCTION: Electrical bioimpedance in tissuesvaries with the ionic concentration of intracellular fluid,extracellular fluid, and dispersion. Performing electricalbioimpedance measurements on human subjects yield aquantitative impedance value but fail to give us insightinto the contribution of each tissue to overall impedanceor change in impedance with tissue conductivity. Thispaper describes a simplistic model of human thoraxcreated and analyzed entirely using electrostaticsinterface in AC/DC module of COMSOLMultiphysics® simulation software to yield informationabout tissue-specific impedance contribution.

HYPOTHESIS:• With an increase in length and width between

electrodes, the overall impedance as well aspercentage contribution of lungs, should increase.

• The transthoracic overall impedance for a modelcorresponding to dimensions of an average humanthorax should be between 10 – 30 Ω.

• Between inflation and deflation change in overallimpedance should be not greater than one percent.

RESULTS: A four-electrode horizontal and crossedconfiguration was used to measure the overallimpedance of the model as well as the percentagecontribution of lung tissue for different combinations oflengths and widths. The results were studied for trendsin change of overall impedance, maxima, and minimathat corresponded well with our hypothesis.

CONCLUSIONS: The model created showscorrespondence with our hypothesis. The results wereverified against measurements from a tissue phantomthat showed correlation. This model may allowbiomedical engineers to rapidly test a hypothesis orstudy electrode configurations before investing time indeveloping or procuring a precise model, thus savingthem time and resources.

REFERENCES:1. Delano Margaret (2018/), A Portable Bioimpedance Spectroscopy System

for Congestive Heart Failure Management (Doctoral Dissertion), Retrievedfrom https://dspace.mit.edu/handle

2. Pettersen et al.,Tutorial on Simpleware ScanFE+IP and COMSOLMultiphysics. J Electrical Bioimpedance, Vol 2, 13-32, (2011)

3. Shuvo et al., Sensitivity Analysis of the Tetrapolar Electrical ImpedanceMeasurement Systems Using COMSOL Multiphysics for the non-uniformand Inhomogeneous Medium, The Dhaka University Journal of Science,

Vol 64, No 1, 7-13 (2016)

Figure 2. (a) Current density due to driving electrode (b) Current density dueto sensing electrode (c) Sensitivity: Conductivity in region C impacts overallimpedance most strongly

Figure 1. Tissue structures included in the geometric model

Table 1. Tissue conductivity values at100 kHz used for simulation

COMSOL Multiphysics® Simulation of Electrical Bioimpedance Impedance in a Simplistic Model of Human Thorax

Preyksha RajanAnalog Devices, Wilmington, MA, USA

A

B

C

(a) (b) (c)

Figure 5. Four electrode configuration used to verify validity of the model(a) Horizontal configuration (b) Crossed configuration

Table 2.Total impedance and percentage contribution of lung tissueto overall impedance

Excerpt from the Proceedings of the 2019 COMSOL Conference in Boston