Relationship Between the Conductivity of Human Blood and Blood Counts

Niko Istuk,Alessandra La Gioia,Barry Mcdermott,Martin O'Halloran,Aoife Lowery,Hamza Benchakroun

doi:10.1109/jerm.2021.3130788

Abstract

Achieving a better characterization of human blood conductivity is of high relevance for medical applications. In this study we measured the complex impedance of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N = 10 human whole blood samples (from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N = 10 oncology patients) at room temperature ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T = 22.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm\; 0.8\;^\circ \mathrm{C}$</tex-math></inline-formula> ) and at body temperature ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T = 36.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm\; 0.4\;^\circ \mathrm{C}$</tex-math></inline-formula> ). The complex impedance was measured using the measurement setup consisting of a custom made four-electrode probe and a commercially available galvanostat. The measured complex impedance data were used to calculate the conductivity of whole blood over the 631 Hz–100 kHz frequency range. The calculated conductivity data is presented and was compared with the literature data. The data from our study is in good agreement with the data available in the literature. Additionally, full blood counts were provided for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N = 8 samples and Pearson correlation coefficient was calculated between the conductivity and blood counts at different frequencies. The three blood count parameters with the highest correlation coefficient are haematocrit (Hct), haemoglobin (Hgb) and red cell count (RBC). The correlation coefficient was shown to decrease as the frequency increases and was the highest at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f = 631 Hz, which is the lowest reported frequency. To our knowledge this is the first study to measure low-frequency (i.e. below 1 MHz) conductivity of whole human blood at body temperature using the four-electrode technique. The results of this study represent an important contribution to the literature, which is currently limited in this area and will help further medical device design.

Highlights

K NOWLEDGE of the electrical conductivity of human blood at low frequencies is fundamental for medical electromagnetic applications
The difference can be explained by blood conductivity increasing with temperature as the mobility of the ions that transport the current increases with temperature and the viscosity of the extracellular fluid decreases [20], [39]
This study introduces a simple and low-cost four-electrode probe as a practical tool for measurements of electrical conductivity of human blood at lower frequencies

Summary

Introduction

K NOWLEDGE of the electrical conductivity of human blood at low frequencies (i.e. below 1 MHz) is fundamental for medical electromagnetic applications. RF ablation has become widely accepted treatment for most atrial and ventricular arrhythmias, including atrial fibrillation (AF) [6] It relies on electrical conduction through the tissue, where RF current is able to pass through the tissue because of the abundance of ionic fluid present in the tissue and since the tissue is not a perfect conductor, RF current causes resistive heating (the Joule effect) [7]. Fricke et al [15] in their 1925 study measured electrical resistance and capacity of calf blood at the frequency range from 800 Hz to 4.5 MHz using a custom two-electrode electrolytic cell [15], [16]. They used a variable frequency oscillator operating at approximately 1 kHz, 5 kHz, 11 kHz and 19 kHz as their alternating current source [17]

Methods

Results

Discussion

Conclusion