Biological model and quantification of fluid changes using an electromagnetic patch sensor

Abstract

Stroke volume (SV) is a critical cardiac output parameter that can offer critical assessments of cardiac function. Utilization of SV measurements can be a valuable tool for early detection for cardio-pathologies, and monitoring pharmacological stimuli in ill patients. Thus, the aim of this study was to develop a non-invasive mobile skin patch sensor - applied like an adhesive bandage which could potentially measure SV. The sensor was designed from a single baseline component comprised of a trace of copper configured into a square planar spiral patch. The sensor was energized by an external radio frequency and produced a resonant frequency response with oscillating magnetic/electric fields which surrounded the sensor. Changes in the magnetic/electric fields due to changes in fluid volume were used to collect stroke volume measurements. An elastic bladder was inserted into the left ventricle (LV) of a bovine heart and a 100 ml syringe was used to simulate stroke volume in the heart. Shifts in the sensor’s resonant frequency were registered as fluid was pumped into the LV chamber. Furthermore, volumetric sensitivity study was conducted to investigate the sensor performance due to different fluid volume increments and to reveal the relationship between fluid volume changes and frequency shifts. An ANOVA analysis followed by a multiple comparison test adjusted for a Bonferroni (alpha =0.05) was done to determine the sensor’s performance in measuring SV. A statistical correlation analysis between the shifts in principal resonance frequency and volume changes were determined through cardiac muscle (R2=0.9849) and in a beaker (R2=0.967). An ANOVA analysis revealed a p-value of <0.01 which indicates the statistical significance of the frequency shifts due to fluid volume increments. This study provides promising data for the ability of an electromagnetic skin patch sensor to be a potential technology for SV measurements in a basic setting.