Numerical modeling of Transcutaneous Electrical Nerve Stimulation and Sensory Nerve Fiber
Transcutaneous electrical nerve stimulation is a non-invasive method of treating patients who have indication of pain. This therapy depends on electrical current and pulse duration applied to electrodes of device. To develop the medical device for pain relief, we investigated a numerical model of transcutaneous electrical nerve stimulation and sensory nerve fiber for a forearm with skin structure. The problem we wish to solve is the action potential of sensory nerve fiber based on electric potential of forearm applied electrical stimulation. The model of the sensory nerve fiber is based on the Hodgkin-Huxley model considering temperature-dependent parameters such as conductance, rest potential, opening and closing rates of ions to describe the temperature of human body 37 ℃. And the model of forearm consists of electrode, stratum corneum, epidermis, dermis, fat, muscle, cortical bone and bone marrow, whose governing equation is Maxwell equation. The electric potential in the model of forearm is coupled with the external current in model of sensory nerve fiber. We use the AC/DC Module and ODE and DAE interfaces in COMSOL Multiphysics® software and solve the models with varied electric current and pulse duration of electrode in the models. The results showed that the threshold current of sensory nerve fiber increased with pulse duration of electrode in model of forearm, and the rise time of threshold voltage in nerve fiber decrease with electric current of electrodes. We need to study more the model by varying the diameter of sensory nerve fiber, the location and diameter of electrodes.
