The electrical impedance of pulsatile blood flowing through rigid tubes: an experimental investigation

Gaw, Richelle L.; Cornish, Bruce; Thomas, Brian

doi:10.1007/978-3-540-73841-1_22

Cited by 8 publications

(5 citation statements)

References 17 publications

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“…Second, the exact origin of these cardiosynchronous signals remains unclear (Adler et al 2017). Thus, for example, the EIT signal during systole has contributions from SV as well as other effects such as heart motion (Proença et al 2015) and the flow-induced reorientation of red blood cells (Gaw 2010). In this case, the EIT signal will not change in proportion to SV if the magnitude of the other contributions is not proportional either.…”

Section: Limitations and Challenges Of Eit-based Monitoring Of Stroke...mentioning

confidence: 99%

“…These are (1) electrode displacement: shifting during a measurement or misplacement between different measurements, (2) issues with electrode contact, e.g. detachment or the drying out of the contact gel, (3) changes in blood conductivity due to changes in hematocrit, (4) changes in lung conductivity due to respiration, liquid redistribution, extra-vascular lung water, etc, (5) respiration-induced thorax excursion, displacement and deformation of heart, lungs and other tissues, (6) posture-and gravity-induced changes such as organ and liquid redistribution, (7) electronic noise and disturbances, (8) impedance changes due to the pulsatile reorientation of red blood cells (Gaw 2010) or other anisotropic structures, e.g. the myocardium (Adler et al 2017).…”

Section: Investigations On Potential Confounding Factorsmentioning

confidence: 99%

“…The result is a slight decrease in HLC and a reduced SV EIT . It needs to be stressed that this remains a simplified explanation, as the heart impedance signal can be influenced by further factors such as heart motion (Proença et al 2015), out-of-(EIT)-plane motion of the heart, σ B dependence on blood flow (Gaw 2010), anisotropy of the myocardium, etc (Adler et al 2017).…”

Section: Belt Displacementmentioning

confidence: 99%

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Limitations and challenges of EIT-based monitoring of stroke volume and pulmonary artery pressure

et al. 2018

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Section: Limitations and Challenges Of Eit-based Monitoring Of Stroke...mentioning

confidence: 99%

Section: Investigations On Potential Confounding Factorsmentioning

confidence: 99%

Section: Belt Displacementmentioning

confidence: 99%

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Limitations and challenges of EIT-based monitoring of stroke volume and pulmonary artery pressure

et al. 2018

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“…These factors can be broadly classified into extrinsic and intrinsic factors. The extrinsic factors mainly include skin conditions [10] and posture [11], and the intrinsic factors include blood temperature [12][13][14][15][16], blood flow rate [17][18][19][20], and hematocrit [13,14,21].…”

Section: Introductionmentioning

confidence: 99%

Temperature Correction to Enhance Blood Glucose Monitoring Accuracy Using Electrical Impedance Spectroscopy

Lee

Son

Zhbanov

et al. 2020

Sensors

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Electrical methods are among the primarily studied non-invasive glucose measurement techniques; however, various factors affect the accuracy of the sensors used. Of these, the temperature is a critical factor; hence, the effects of temperature on the electrical properties of blood components are investigated in this study. Furthermore, the changes in the electrical properties of blood according to the glucose level are corrected by considering the effects of temperature on the electrical properties. An impedance sensor is developed and used to measure whole blood impedance in 10 healthy participants at various temperatures and glucose levels. Subsequently, the conductivities of the plasma and cytoplasm were extracted. Changes in the electrical properties of the blood components are then analyzed using linear regression and repeated measures ANOVA. The electrical conductivities of plasma and cytoplasm increased with increasing temperatures (plasma: 0.0397 (slope), 0.7814 (R2), cytoplasm: 0.014 (slope), 0.694 (R2)). At three values of increasing glucose levels (85.4, 158.1, and 271.8 mg/dL), the electrical conductivities of the plasma and cytoplasm decreased. These tendencies are more significant upon temperature corrections (p-values; plasma: 0.001, 0.001, cytoplasm: 0.003, 0.002). The relationships between temperature and electrical conductivity changes can thus be used for temperature corrections in blood glucose measurement.

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“…• The orientation of red blood cells. During pulsatile flow, the orientation of red blood cells changes, which has been shown to affect the impedance of the blood (Gaw, 2010).…”

Section: Bioimpedance Of Perfusionmentioning

confidence: 99%

Electrical Impedance Tomography for Perfusion Imaging and Monitoring

Stowe¹

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Electrical impedance tomography (EIT) is a medical imaging technology that uses boundary electrodes to inject stimulus currents and measure the resulting potential distributions. These potentials are measured using electrodes which are in turn used to reconstruct conductivity changes within the body.EIT has been studied for its ability to image both the flow of blood and the delivery of blood to a tissue (perfusion). However, cardiac-related signals are challenging to image accurately due to their small amplitude and the limited sensitivity of EIT systems to impedance changes deep in the body. This thesis presents techniques to improve perfusion imaging with EIT by generating more accurate meshes and using internal electrodes to obtain higher sensitivity in the centre of the body. This work develops a tool to generate accurate, customized meshes from diagnostic computed tomography (CT) images, and a technique to reconstruct images with internal electrodes. Custom models reconstructed the location of impedance changes due to ventilation with higher accuracy, and internal electrodes yielded an increase in internal sensitivity over traditional external configurations. Shifting the position of electrodes on an internal probe by as little as 1% of the tank radius in simulation created artefacts in images reconstructed using existing approaches without motion correction. A novel technique to correct for probe motion is presented that improved reconstruction accuracy and reduced background noise compared to existing techniques. The presented work contributes to increasing internal sensitivity of EIT measurements and demonstrates that refined meshes and internal electrodes may improve measures of perfusion and help to make EIT a viable tool for continuous perfusion monitoring at the bedside.iii Thank you to Dr. Étienne Fortin-Pellerin and the team at Université de Sherbrooke for their support with so many experiments, and welcoming me into their lab.I would also like to thank Dr. Alistair Boyle for his valuable insights into the field of EIT and my colleagues who have made my time at Carleton so enjoyable.Finally, a huge thank you to my family. My parents, Marlys and Doug, and my sisters, Alyssa and Caitlyn have supported this work in so many ways, both in the workshop helping with prototypes and proofreading. A special thank you to my partner Sana for her patience, help and support along this journey.

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The electrical impedance of pulsatile blood flowing through rigid tubes: an experimental investigation

Cited by 8 publications

References 17 publications

Limitations and challenges of EIT-based monitoring of stroke volume and pulmonary artery pressure

Limitations and challenges of EIT-based monitoring of stroke volume and pulmonary artery pressure

Temperature Correction to Enhance Blood Glucose Monitoring Accuracy Using Electrical Impedance Spectroscopy

Electrical Impedance Tomography for Perfusion Imaging and Monitoring

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