Biomedical subjects

W A Waugaman

Publications and source records attributed to W A Waugaman.

3 recordsLinked to original sources

PubMed2001

Prediction of internal electric current distribution from surface application in atrophied muscle tissue.

The use of surface electrical stimulation therapy for clinical rehabilitation has created the need for an improved modeling method to predict internal current density. A method was developed to model quantitatively the current density delivered to an atrophied muscle. Some stimulation protocols do not produce measurable physiological effects, such as muscle contraction. Therefore, traditional response-based current density modeling cannot be used. Additionally, lumped circuit models do not provide the resolution needed to optimize electrode size, shape, and placement. The quantitative approach developed here can be used to optimize electrical stimulation protocols in abnormal muscle tissue. In this study, the finite element method (FEM) is used to model the low intensity electric current stimulation resulting from surface application. FEM provides the ability to model complex tissue properties found in living tissue. A leg of lamb was modeled because its size and level of tissue complexity is similar to that of a human child's thigh. Voltage gradient measurements were made upon a sacrificed leg of lamb during the application of bipolar stimulation. These measurements were made at numerous points in the stimulated leg of lamb and allowed the mapping of the current density. The leg of lamb was then sliced and photographed to be able to create the finite element model. The empirical data compared favorably to the results of the FEM model, thus verifying the method. This FEM model was then modified to study the effects of muscle atrophy on electric current densities. This modeling method will ultimately lead to improved stimulation protocols and better clinical treatment.

Animals↗

PubMed1999

Verification of the finite element method to model subthreshold electrical current density in saline.

Therapeutic electrical stimulation (TES) is a rehabilitative stimulation therapy for individuals with neuromuscular disorders. TES uses subthreshold transcutaneous electrical stimulation to cause muscle growth and neuron sprouting through increased blood flow. To optimize TES therapy, a new method was required to determine the electrical current density in the target muscle. This is because TES's subthreshold stimulation intensity does not produce any measurable physiological effect. The finite element method (FEM) was the numerical modeling method chosen. FEM provides the ability to the model complex properties found in living beings, such as different tissue types and anisotropic tissue properties. TES uses a 35 Hz biphasic waveform. At this low frequency, the quasi-static approximation was used. This allows the heat transfer model solution to be used to find the steady state electric field solution. The goal of this paper is to show that the heat transfer results are the same as the electric field measurements made in a biological phantom. Laboratory measurements were made in a one liter cylinder of normal saline using bipolar stimulation. Electric field measurements were made using silver chloride electrodes at various points in the stimulated solution. This allowed the mapping of the electric potentials. The empirical data compared favorably to the results of the FEM thus validating in the method and assumptions. Finite element modeling provides an accurate method to visualize the electrical current densities resulting from bipolar stimulation. The FEM can now be used to determine the optimal electrode configuration for TES and other electrical stimulation protocols. This computer modeling method will ultimately lead improved patient results.

Computer Simulation↗

PubMed1997

Electrical current density model from surface electrodes.

The goal of this research is to determine the optimum electrical current for subthreshold electrical stimulation. The first step is to collect atrophied muscle impedance data from children with neuromuscular disorders using Bioelectric Impedance Analysis (BIA). Then to incorporate this impedance data into a model using the 3-D Finite Element Method (FEM). This will allow the evaluation of electric current densities in the target muscle resulting from Therapeutic Electrical Stimulation (TES). Using the FEM, optimum electrical stimulation parameters, levels, and electrode placement can be determined. The FEM will provide the first means to determine the quantity of electric current flowing through the target muscle from surface electrode stimulation. TES is adding new life to electrical stimulation therapy. TES is low intensity (subthreshold), long duration transcutaneous stimulation using surface electrodes. TES effects muscle growth and peripheral nerve sprouting leading to increased functional control and sensation. The initial parameters used in TES have been proven clinically to be effective for use in rehabilitation therapy for people with neuromuscular disorders. This research is the first step towards optimization of the TES protocol. Ultimately, the results will lead to improved quality of life for children with neuromuscular disorders.

Body Composition↗