Electrostimulation involves contacting a motor nerve by means of applied voltage. This contacting causes an action potential to reach the muscle, causing it to contract. Therapeutic electrostimulation is used primarily for peripheral paralysis and is intended to prevent muscle atrophy.
What is electrostimulation?
Electrostimulation is therapeutic stimulation by an applied voltage source. Electrostimulative procedures are used primarily for nerve deficits. Electrostimulation is therapeutic stimulation by an applied voltage source. Electrostimulative procedures are used primarily for nerve deficits. When peripheral nerves of the body fail, there is often a breakdown of muscle cells in the area supplied by the paralyzed nerve, especially in the arms and legs. This degradation is related to the fact that the muscles do not reach electrical signals through the nerve, The signals from the nerve can be replaced by electrostimulating therapies. In such a therapy session, attached electrodes send small surges of electricity into the tissues to control the affected nerve. The control causes stimulating signals to reach the threatened muscle, resulting in a muscle contraction. Due to the contractions induced in this way, ideally no atrophy of the paralyzed muscle occurs. Human muscles show varying degrees of response to different types of current modulation. In most cases, voltage waveforms with an exponential progression are best suited for electrostimulation. In addition to this application, therapeutic measures are also used on men with anejaculation to stimulate ejaculation.
Function, effect, and goals
Functional electrostimulation corresponds to the electrical stimulation of a specific muscle or muscle group. The procedure can take place directly or indirectly. The electrical signal stimulates motor nerves, which trigger muscle contraction. Implanted functional electrical stimulation takes place, for example, with the pacemaker. Depending on the particular damage, the regular stimulating signal of the pacemaker excites the heart muscle in the region of the right atrium or in the region of the right ventricle. The respiratory pacemaker is also based on implanted functional electrical stimulation and stimulates mainly the phrenic nerve. Other applications of the implanted form are the bowel pacemaker and the bladder pacemaker, which stimulate the muscles involved in excretion to contract. Another field of application of electrostimulation opens up with the cochlear implant of hearing impaired people. The implant electrically stimulates the auditory nerve, allowing hearing even after severe hearing loss. This type of electrical stimulation irritates different regions of the basilar membrane, stimulating ganglion cells in the hearing organ. Each nerve stimulation requires an applied field strength with a certain gradient strength that can trigger an action potential in the contacted nerve. The potential thus triggered travels along the motor nerve to the motor end plate of a muscle. At the muscle, the stimulation again triggers an action potential and thus moves the triggered muscle to contract. However, muscle cells can also be stimulated directly. Electrical stimuli for direct muscle excitation are much larger and last much longer than those for stimulation of specific nerves. For both nerve and muscle electrostimulation, surface electrodes are applied to the patient’s skin. Normally, these measures take place within a rehabilitation facility. By means of changes in the stimulation frequency, electrostimulation stimulates the individual areas of the muscle fibers to varying degrees. Frequencies up to 200 Hz activate mainly the fast muscle fibers. Those up to 10 Hz improve the endurance capacity of the slow muscle fibers. Direct muscle electrostimulation is equivalent to training and can thus be applied to top athletes, for example. The now effective application of direct muscle electrostimulation refers to denervated muscles after permanent peripheral paralysis and uses pulses of up to 300 MS width. Stimulation intensities range up to 250 mA.
Risks, side effects, and hazards
As a therapeutic method, electrostimulation is associated with some risks and side effects.A person’s body is sensitive to electrical currents. For this reason, small voltages below 40 volts can already cause negative effects if applied to unfavorable conditions. These unfavorable conditions include, for example, highly conductive sweat. In individual cases, electrostimulation thus causes injuries such as minor burns or functional impairment of peripheral nerves. Since improper use can also impair the conduction of excitation in the heart muscle cells, life-threatening cardiac arrhythmias can occur in extreme cases. In the context of direct muscle stimulation, pain can also occur as a side effect of electrostimulation. Some patients experience low-frequency stimulation current only as an unpleasant pulling sensation. Others complain of extremely painful sensations. In patients without appropriate innervation, these side effects take care of themselves. All other patients are now usually treated with medium-frequency current for direct muscle stimulation, which corresponds to frequencies above 1000 Hz and is sensitively non-stressing. Electrical resistance to electrical stimuli is inversely proportional to frequency. According to experience, frequencies of about 2,000 Hz in modulated currents are most effective. Modulated medium frequency is already used in a standardized way by certain therapy devices and training systems. Both electrostimulation of nerves and stimulation of muscles can cause skin rashes in the area of the applied electrodes. As a rule, such rashes are reversible and disappear after a few hours. However, patients with allergies to certain adhesives should make these allergies known to their therapist. In absolutely exceptional cases, sensory disturbances remain on the skin after electrostimulation, resulting in permanent insensations. Such insensations can correspond, for example, to a persistent numbness or a disturbance of the warm-cold sensation. Despite the possible risks, most patients tolerate electrostimulation well. Some even find the pulses relaxing.
