Bio-Impedance Measurement Optimization for High-Resolution Carotid Pulse Sensing

Abstract

Continuous hemodynamic monitoring is important for long-term cardiovascular healthcare, especially in hypertension. The impedance plethysmography (IPG) based carotid pulse sensing is a non-invasive diagnosis technique for measuring pulse signals and further evaluating the arterial conditions of the patient such as continuous blood pressure (BP) monitoring. To reach the high-resolution IPG-based carotid pulse detection for cardiovascular applications, this study provides an optimized measurement parameter in response to obvious pulsation from the carotid artery. The influence of the frequency of excitation current, electrode cross-sectional area, electrode arrangements, and physiological site of carotid arteries on IPG measurement resolution was thoroughly investigated for optimized parameters. In this study, the IPG system was implemented and installed on the subject’s neck above the carotid artery to evaluate the measurement parameters. The measurement results within 6 subjects obtained the arterial impedance variation of 2137 mΩ using the optimized measurement conditions, including excitation frequency of 50 kHz, a smaller area of 2 cm2, electrode spacing of 4 cm and 1.7 cm for excitation and sensing functions, and location on the left side of the neck. The significance of this study demonstrates an optimized measurement methodology of IPG-based carotid pulse sensing that greatly improves the measurement quality in cardiovascular monitoring.

Sensor-Location-Specific Joint Acquisition of Peripheral Artery Bioimpedance and Photoplethysmogram for Wearable Applications

“…Classically, the electrode placements for brachial artery EBI monitoring are not densely located, and the Z ( t ) varies on a larger scale in the published works [ 50 ]. The same applies to the carotid artery, where our measured Z ( t ) exceeds the values derived, e.g., in [ 27 ]. For the posterior tibial artery, respective comparative measurement results of EBI are unavailable, constituting an unexplored area.…”

“…Thereat, the electrodes may be targeted to the ulnar [ 24 ] and radial artery [ 9 , 25 ] or both [ 10 , 26 ]. The relative closeness of the carotid artery to the aorta has shown good results in pulse sensing through EBI measurement [ 27 ]. Also, the brachial artery has been considered, e.g., in EBI-based cardiac output and stroke volume estimation [ 28 ].…”

Intelligent Bio-Impedance System for Personalized Continuous Blood Pressure Measurement

“…The IPG technique is based on the electric impedance measurement that applies the alternating current into a local area of the body, and then measures the voltage signal. In hemodynamic studies, an IPG-based measurement can extract arterial impedance induced by a small variation in the blood volume [25,26], as shown in Figure 1a. Based on the Bramwell-Hill equation, as in Equation ( 1), the BP has a strong correlation with the cross-sectional area of the artery.…”

Neckband-Based Continuous Blood Pressure Monitoring Device With Offset-Tolerant ROIC

“…IPG is non-invasively measured by detecting the change of body impedance. Therefore, if the IPG is measured around the neck, it is possible to obtain more accurate PTT than the PTT calculated using the ECG and PPG because the IPG signal is induced from the change of blood volume in the carotid artery [19].…”