ELECTRICAL STIMULATOR

Nerves and muscles in the body produce electric potentials when they operate, and conversely they can be made to operate by electrical stimulation. Electrical stimulators are widely used in hospitals.

In the physiotherapy department stimulators exist which may provide direct, alternating, pulsating, or pulsed waveforms, and are used to exercise the muscles by stimulation through Electrodes placed on the skin. The apparatus required for this is often called a Faradic treatment unit, or electrotherapy set.

Electrical stimulators are also sometimes used by anaesthetists during surgery to demonstrate the muscular response to stimulation of a nerve (usually applied to the arm or wrist via Electrodes on the skin). Muscle relaxants used during surgery should abolish the response.

Stimulators exist now which are used for the relief of pain. These transcutaneous electrical neural stimulators (TENS) appear to suppress other pains in the same general area where the stimulation is applied. Electrical stimulation of trigger points is also claimed to be effective. Known trigger points (from acupuncture) are said to display lower skin resistance than other sites. The use of TENS at these points may produce therapeutic effects remote from the sites in question. The mechanism by which these effects are produced is poorly understood. The same can be said of electroanaesthesia and electrosleep.

Electrical stimulators are also used in the neurology department for diagnostic tests on the nervous system. A common test measures nerve conduction velocity using stimulation via skin Electrodes but stimulation may also be applied directly to nerve trunks or into the brain during specialized procedures, but these are less common.

Cardiac pacemakers are electrical stimulators which apply short pulses at the desired heart rate to a site within the heart. These pulses are intended to trigger (prompt) the natural pacemaking mechanisms of the heart and may be required for a short period (in which case an external stimulator may be used with a long wire leading to the heart) or they may be implantable devices remaining in for a number of years before new batteries need fitting.

Other types of stimulator exist including those used to cause contraction of leg or arm muscles as an aid to rehabilitation after spinal injuries, injury to peripheral nerves or muscles, and those stimulators intended for use on the muscles of the pelvic floor as a treatment for incontinence. Electrodes for such devices may be implanted, indwelling, transcutaneous (needles), or surface.

Electrical stimulators may have controls to set the pulse length, pulse repetition frequency, pulse amplitude, and triggering modes. Modern stimulators should either be battery operated or fully electrically isolated.

Content and Design Copyright 2000 Dr. Malcolm C Brown.  See Title Page for more details