Tens and interferential units are both used to block the pain signals along sensory nerve routes and often are used as natural and effective pain management. Interferential Stimulation differs from TENS because it allows a deeper penetration of efficacious electrical current in the tissue with more comfort (compliance) and increased circulation. ‘For example, at a frequency of 4,000 Hz (Interferential unit) capacitive skin resistance is eighty (80) times lower than with a frequency of 50 Hz (in the TENS range).
TENS (Transcutaneous Electrical Nerve Stimulation) was designed to stimulate sensory nerve endings in order to decrease the perception of pain. The stimulus blocks pain signals passing along the nerves to the central nervous system. There are many articles that also say TENS will produce excess production of natural pain killers which will control pain but in practice this methodology with TENS rarely is efficacious. TENS blocks pain signals to the brain/spinal cord. TENS stimulation is characterized by biphasic (positive/negative) balanced charges and user selectable pulse width and pulse rate.
Interferential therapy (IF/ IFC) is often described as ‘deep TENS’. Interferential therapy is two high frequencies of 4,000 cycles per channel, overlapping, resulting in 8,000+ pulses per second in the affected area. That enables the electrical currents to penetrate deeper into the tissues. The extra frequency allows the frequency over 8,000,(1- 150) the benefit of low frequency stimulation without the uncomfortable effects of TENS. Interferential therapy offers not only pain relief, but also contributes to acceleration in healing, increased blood flow and edema reduction.
The basic goal of interferential current therapy is to give a pleasant sensation during treatment and achieve deeper tissue penetration allowing carryover pain relief. The uncomfortable sensation felt by many patients using TENS is due to the resistance of the skin to the passing electrical currents. The level of discomfort is inversely proportional to the frequency of stimulation. Hence, the lower the frequency applied, the greater is the discomfort felt. Interferential current therapy uses two medium frequencies applied at the same time in such way that their paths cross and interfere with each other. The interference between them leads to changes producing modulated frequency that has the same therapeutic effects as low frequency stimulation, but without the normal side effects of unpleasant sensation or discomfort.
Interferential therapy is safe and has no side effects. While the interferential therapy is very effective, it causes a minimum skin sensation and the level of discomfort related to the electrical stimulation.
Conditions that respond to TENS & Interferential include the following:
-Post Amputation Pain/Phantom Limb Pain
-Tension – Migraine
Tens has been recognized as efficacious and the rent and purchase paid by almost all major insurance companies for decades, including Medicare (HCFA), when used for chronic pain. Medicare will pay for an interferential treatment in a health facility but does not pay for the rental/purchase of an interferential unit. Many patients have not had the money to pay out of pocket for an interferential unit even though the benefits are obtained in the clinical setting . In certain instances a patient may have coverage for “DME”, durable medical equipment, such as wheelchairs, potty seats, canes, crutches, and walkers. If the patient has DME coverage then in almost all situations Interferential may be covered.
The combination of TENS and IFC in one unit now means when the unit is prescribed for chronic pain that even Medicare will cover it. The new combination IFC/TENS device with both modalities will open up new treatment parameters for patients now that an IFC unit can be rented or purchased by a patient.