Examination of parameters in transcutaneous electrical nerve stimulation effectiveness

Pain is the oldest medical condition and has been referenced through the ages. TENS is a non-invasive treatment for pain. Despite conflicting reports of treatment outcomes, TENS has enjoyed widespread clinical utilization. Seminal work by Sluka and colleagues reported low frequency TENS produces anti-hyperalgesia through µ-opioid receptors and high frequency TENS produces anti-hyperalgesia through ä-opioid receptors in an animal model of inflammation. The experimental results suggested that pain can be reduced by both high and low frequency TENS but by differing opioid receptors. These important findings require translational experiments to be conducted in humans.

Providing an adequate placebo for experimental investigation of any physical intervention presents as a challenge. An improvement in the placebo intervention is critical to ascertain the true effects of TENS on painful conditions. Clinical TENS experiments often only examine a single outcome - resting pain. Recent work suggests TENS is less effective on resting pain as compared to movement pain. Investigation to determine which outcome measures (pain at rest, movement pain, pain sensitivity, and function) are most likely to be affected by TENS in human subjects with pain are critical to inform the design of future studies.

The least investigated parameter for application of TENS electrode site determination. One method of selection employs a technique of finding points on the skin with suspected lower impedance. To date, no literature exists to determine the effectiveness of this clinical practice and speculation has existed for decades regarding the existence of distinct electrical properties associated with specific points on the body.

This series of experiments accomplishes the goals of improving the TENS placebo, testing established parameters from basic science experiments in a patient population, testing multiple outcome measures to direct future investigation; and examined the effect of electrode site selection in TENS analgesia. These experiments were the first to establish a placebo that can 100% blind the TENS examiner, to test this placebo in a patient population, and to show that although there are differences in impedance between optimal and sham sites, that this difference had no effect in the amount of analgesia produced by TENS.