Since 1953 interventional therapy has been used in hospitals and hospitals to immediately provide pain relief for chronic and acute pain patients. Originally developed in Austria by Dr. Hans Nemec it is one of a number of electrical stimulation techniques used in modern pain control by physiotherapists, MD's, and DC's.
Interferential therapy arrived roughly the same time as did the discovery of the use of cortisone, phenylbutazone and other new drug treatments. It was relegated as a form of palliative treatment and almost led to its virtual disappearance but for its use in clinics and hospitals for patients needing immediate pain relief.
During the late 1960s and 70s it was found that many of the new drugs also provided very undesirable side effects and, as more drugs were coming down the pipeline, there developed some serious side effects including death when they were combined, or used in conjunction with , other pain and non pain medications. Often the effect of the drugs addressed in not pain cessation but in altered levels of consciousness which affected daily living.
It is known that external electrical stimulator can excite tissues, specifically neural tissue which affects movement, and sensory perceptions. Certain excitable neural tissues and the rate (frequency) for excitation are as follows:
· 0-5 Hz sympathetic nerves
· 0-10 Hz unstriped muscle
· 1-50 Hz motor nerves
· 10-150 Hz parasympathetic nerves
· 90 – 150 Hz sensory nerves
One of the problems in stimulating the neural tissue is the dry outer layer of the skin, corneal tissue, has a reliably high level level and impeded the flow of the electrical current to the target neural tissues. The high resistance is what led to the development of interventional therapy.
Basically interferential is called such due to the "interference" of two currents crossing each other and the summary (beating) of those currents leading to a new current. This new current is the stimulant current that affects the neural tissue. The purpose of the higher frequency is with increased frequency comes increased penetration. There is no magic to the interferential frequencies of 4,000 and 4001 to 4,150. Generally speaking if the frequency were increased to 10,000 then the potential of less resistance may be better but the practicality is to find the optimum frequency that is therapeutically efficient and technologically achievable.
In theory when two currents are administrated with some form of a crossover pattern there occurs a summation of the electrical energy that is greater than either individual current as a stand alone current. It is along the point of crossover energy that the stimulatory frequency is in the range of 1 – 150 pulses per second (PPS), another term for frequency. The neural tissues are now excited by the new current created.
In pain control the sensory nerves are the targeted tissues that affect pain relief. It is the stimulation of these nerves that "block" (Melzack / Wall Gate Control Theory) the transmission of the pain impulse to the spinal cord for sensory perception in the brain.
For clinical use interferential has been used due to its immediacy to block the transmission as the patient is treated. When the patient enters the clinic or doctor's office it is with the active transmission of the pain impulse to the brain. During the treatment the cross currents of the differential treatment interfer with the pain stimulus by stimulating the sensory nerves, rather than allowing the pain impuls of the C-fibers (carrier of the pain impulse) to reach the spinal cord. Following treatment most patients find the treatment has provided what is called "residual" or "carryover pain relief" and the restoration of the pain message is delayed for some time period following interferential treatment.
When the differential treatment can be submitted on an as needed basis, outside a medical facility, the patient can effect the delay of the return of the pain stimulus for hours, progressing to days, weeks or months.