Electronic Stimulation Essay, Research Paper

Medicine and electronics are rapidly becoming a common partnership. Electronics and medicine has been around for over a hundred years. This application can be seen in early X-ray machines, as well as early doctors and healers who felt that electricity possessed something special that assisted the healing process of many illnesses and injuries. But it has not been the last forty to fifty years that the development and refinement of electricity as medical agent has occurred. Today the medical field can not imagine itself without the assistance of electricity and electronic components.

In recent years some of the major development has occurred in one particular field of

Medicine, electric stimulation. Electric stimulation is the application of electric current in treatment without the generation of intense heat. This includes electric stimulation of nerves or muscles, passage of current into the body, or use of interrupted current of low intensity to raise the threshold of the skin to pain.

Studies suggested this therapy is applied to conditions such as ulcers, traumatic or burn wounds, osteoarthritis, and cancer. Electrical stimulation is simply the application of electrical pulses to the body, whether it is for function or therapy. The classical and common example is that of the cardiac pacemaker. The range of clinical uses of electrical stimulation has and is growing wider and includes: pain relief (often known as TENS – Transcutaneous Electrical Nerve Stimulation), maintaining or increasing range of movement, muscle strengthening, facilitation of voluntary motor function, and orthotic training or substitution.

Functional Electrical Stimulation (FES) is a branch off of electrical stimulation. The term FES is applied to systems, which attempt to restore, lost or impaired neuromuscular function. This would include such things as standing and walking in cases of paraplegia, by the application of electrical pulses to neural pathways or, but less often, directly to muscles. FES is also sometimes known as Functional Neuromuscular Stimulation or FNS. (http://medicaledu.com:80/estim.htm, 1999)

At the electrode-tissue interface, where the electrode and actual body come into contact, a conversion occurs between the current of electrons passing through the wires and the current of ions moved

within the tissue. Then through this externally applied current, the depolarisation of nerve and muscle to threshold is produced by the transport of ions across the tissue membrane. There are several factors that determine whether sufficient current flows is taking place: impedance of body tissues, electrode size and position, and stimulation parameters. The conductivity of body tissues is related to their water and ion content. Muscle is a good conductor, but conducts better in the longitudinal direction of its fibers than in the transverse one. This also adds to the importance of electrode positioning because it can affect the current required for stimulation. With surface electrical stimulation the effect of the electric current (the

current density) diminishes with depth of tissue.

FES involves depolarizing nerve/muscle fibers via externally applied electric current. Once depolarised these fibers conduct action potentials as occurs in healthy tissue. The electrical pulses applied may be: Monophasic, these waveforms tend to be asymmetric biphasic as the net charge built up in the body by the waveform discharges.

Charge Balanced, is a pulse type that uses a no net charge that is introduced to the body. This is particularly important for some types of enervated muscle stimulation and for implanted electrodes, where electrolysis at the electrode tissue interface could take place if there was a non-zero net charge. These techniques are generally divided into three sub-categories: Faradic, Galvanic, and Interferential.

It is generally the case that faradic stimulation is applied. Faradic stimulation is used for

innervated muscle, i.e. when the lower motor neurons are intact. Stimulation is applied via the nerves often at the muscle motor points. The nerves depolarisation leads onto muscular contraction. Faradic stimulation can be considered to be ac with pulse widths