A piece of equipment commonly used by physical therapists is the interferential current electrical stimulator. This machine produces electrical currents (~4000HZ) that pass through the affected area to be treated. This current tends to penetrate deeper than other electrical modalities and has a number of physiological effects that have therapeutic value.The physiological effects include:
- An increase in localized blood flow which can improve healing by reducing swelling (the additional blood flowing through the area takes edematous fluid away with it)
- The stimulation of local nerve cells that can have a pain reducing/analgesic effect due to potentially blocking the transmission of the pain signals (pain gate mechanism) or by stimulating the release of pain reducing endorphins (opiod mechanism)
The electrical current is applied to the affected area using four electrodes. The four electrodes are placed in such a way that the two currents produced cross each other in the affected area. Where the two currents meet, they actually ‘interfere’ with each other; hence the name ‘interferential.’
During treatment the patient will feel a tingling or ‘pins and needles’ sensation at the contact area of the four electrodes and may also feel the tingling sensation throughout the area being treated. This sensation may continue for a brief period following treatment as well. The intensity of the current should be increased within the patient’s comfort level. A stronger current will usually have a more beneficial effect but the intensity should not be turned up so high as to cause pain.