The impact of ion drift in a Transcutaneous Electrical Stimulation model
(2022) BMEM01 20222Department of Biomedical Engineering
- Abstract
- A major area of research in neuroscience is the effect of stimulating nerves into activation from extrinsic stimuli. This is commonly done with electric currents and external skin-contact electrodes. Research has shown that this method is efficient for producing muscle activation and that different current waveforms produce differing levels of activation and discomfort. This report aims to augment existing transcutaneous electric stimulation models with the effects of ion drift in the electric field caused by the electrodes and investigate how it affects nerve activation. This was done by creating a representative FEM model of the human forearm and directly simulating the effects of introducing ion drift into the model. Models for ionic... (More)
- A major area of research in neuroscience is the effect of stimulating nerves into activation from extrinsic stimuli. This is commonly done with electric currents and external skin-contact electrodes. Research has shown that this method is efficient for producing muscle activation and that different current waveforms produce differing levels of activation and discomfort. This report aims to augment existing transcutaneous electric stimulation models with the effects of ion drift in the electric field caused by the electrodes and investigate how it affects nerve activation. This was done by creating a representative FEM model of the human forearm and directly simulating the effects of introducing ion drift into the model. Models for ionic effects on both electrical conductivity and charge density were included. Simulations showed a very limited effect on nerve activation and that the contributions from changes in ion concentration due to drift was small. Thereafter a 2D-axis symmetric model with the more accurate and costly Nernst Planck Poisson equations showed that the size of charge accumulation and its screening effect on the potential field were both small. Lastly it was studied wether the augmented model could account for different current waveforms yielding different nerve activation patterns, however this could not be replicated. The conclusion from this work is thus that ion drift on the macroscopic scale as modelled here only gives small, almost non-significant results. (Less)
- Popular Abstract
- Can ions drift in a electric field be modelled to impact nerves activation answer? A popular scientific summary
This report studies if it is possible to more accurately predict how nerves activate during electrical stimulation if the electrical effects of ions are included. This was accomplished by developing a new model for how ions change the way human tissue conducts electricity and by simulating these effects in computer models.
The nerves we have in the human body can be activated to cause muscle contractions. This normally happens when a nerve cell receives a signal from another nerve cell, however this can also be achieved by exposing the nerve to an electric current. A common technique for this is to attach electrodes to the... (More) - Can ions drift in a electric field be modelled to impact nerves activation answer? A popular scientific summary
This report studies if it is possible to more accurately predict how nerves activate during electrical stimulation if the electrical effects of ions are included. This was accomplished by developing a new model for how ions change the way human tissue conducts electricity and by simulating these effects in computer models.
The nerves we have in the human body can be activated to cause muscle contractions. This normally happens when a nerve cell receives a signal from another nerve cell, however this can also be achieved by exposing the nerve to an electric current. A common technique for this is to attach electrodes to the skin and to carefully pass current between them until the desired muscle activates. Because the ions are charged they "wander" towards its opposite charge in an electric field. This means that if an electric field is sufficient strong it is possible to move around enough ions to change the electrical properties of the tissue, and thus change how electricity passes through the nerves.
This report attempts to model the effects ions have on nerve activation by taking into account and modelling two phenomena; Electrical conductivity and charge accumulation. Electrical conductivity is a measure of how easy an electric current passes through a material, and by changing the concentration of ions using the electric field it is possible to change this property. Charge accumulation is what happens when ions of similar charge "pool up" in the same area and create their own electric field, which interferes with the electric field from the electrodes. Both these effects were modelled mathematically and then simulated in numerical simulations.
Lastly it was studied if the ionic effects could help explain the observed phenomenon that differently shaped electric pulses produce different outcomes in experiments. It has been shown that different pulse shapes lead to different levels of comfort and muscle activation in patient, but conventional models of nerve activation cannot account for this fact.
Unfortunately it was found that these ionic mechanisms could not significantly improve prediction accuracy or help explain the observed difference between different pulse shapes. This could be due to the modelling simplifications that were made, or it might be implying that ionic effects are irrelevant on the macroscopic scale. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9100821
- author
- Tuvesson, Oscar LU and Blåe, Erik LU
- supervisor
- organization
- alternative title
- Jonflödens påverkan i en modell av transkutan elektrisk stimulering
- course
- BMEM01 20222
- year
- 2022
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- TES, neuron activation, ion drift, conductivity, COMSOL, FEM
- language
- English
- additional info
- 2022-20
- id
- 9100821
- date added to LUP
- 2022-09-27 12:47:48
- date last changed
- 2022-09-27 12:47:48
@misc{9100821,
abstract = {{A major area of research in neuroscience is the effect of stimulating nerves into activation from extrinsic stimuli. This is commonly done with electric currents and external skin-contact electrodes. Research has shown that this method is efficient for producing muscle activation and that different current waveforms produce differing levels of activation and discomfort. This report aims to augment existing transcutaneous electric stimulation models with the effects of ion drift in the electric field caused by the electrodes and investigate how it affects nerve activation. This was done by creating a representative FEM model of the human forearm and directly simulating the effects of introducing ion drift into the model. Models for ionic effects on both electrical conductivity and charge density were included. Simulations showed a very limited effect on nerve activation and that the contributions from changes in ion concentration due to drift was small. Thereafter a 2D-axis symmetric model with the more accurate and costly Nernst Planck Poisson equations showed that the size of charge accumulation and its screening effect on the potential field were both small. Lastly it was studied wether the augmented model could account for different current waveforms yielding different nerve activation patterns, however this could not be replicated. The conclusion from this work is thus that ion drift on the macroscopic scale as modelled here only gives small, almost non-significant results.}},
author = {{Tuvesson, Oscar and Blåe, Erik}},
language = {{eng}},
note = {{Student Paper}},
title = {{The impact of ion drift in a Transcutaneous Electrical Stimulation model}},
year = {{2022}},
}