Electrical Stimulation: Can It Help Facilitate Wound Closure?
While there are varied modalities available to help manage stubborn wounds, this author suggests that electrical stimulation may play an adjunctive role. Accordingly, he reviews the current literature, theories and practical application of electrical stimulation in wound care.
As the field of wound care progresses clinically from a focus on the gross and cellular levels to a better understanding of the subcellular and biochemical levels, our approach to treatment has progressed from passive dressing modalities to advanced wound care products including mechanically driven wound care modalities. Mechanical wound care products incorporate physical modalities including pressure, ultrasound, radiofrequency and electrical stimulation.
As our understanding of the inner workings of cells increases, we begin to try to manipulate cells in the most positive way to induce quicker and better wound healing. The best of these modalities not only alter the structure of the cells involved but also induce the biochemical actions that cause healing. The ultimate goal is not only to heal the current wound but also to generate healing so the tissue is in such a condition as to minimize the risk of ulceration recurrence.
The “current of injury” and exogenous mimicking of the phenomenon for wound care is not a new concept. Ojingwa finds reference to the use of electric stimulation as far back as the 17th century. He relates the use of an electrostatically charged gold leaf to enhance the healing of smallpox lesions.1
Barker and colleagues observed that wounds in the skin induce an instantaneous current flow out of the wound (driven by the transepithelial potential difference). This establishes a steady direct current (DC) electromagnetic field at the wound of up to 200 mV/mm that persists until re-epithelialization is complete.2 This translates into the fact that in the presence of a wound, our skin battery leaks its electric potential until such time as the wound heals.
This electric field is important for generating a natural biological galvanotaxis, which draws cells and neural tissue to the wound to generate healing. In a chronic wound, this electromagnetic field is disrupted and therefore inhibits cellular regeneration. If electrical signals play a role in the stimulation of wound repair, then one could expect that exogenous application of an electrical current to chronic wounds could mimic the body’s bioelectrical currents and enhance tissue healing processes.
Cruz and co-workers found the current of injury varied in specific ways during the regeneration process with the current ceasing to flow as healing completes or stalls.3 Foulds and colleagues, in demonstrating the “skin battery,” showed that a voltage is consistent across the epidermis.4 They note that the outer surface of the skin is negatively charged with respect to the positively charged dermis.
A Guide To The Theoretical Basis Of Electric Stimulation
While the mechanism by which electric stimulation changes the cellular environment is still unknown, researchers have put forth a number of hypotheses. Bourguignon and colleagues propose that electric stimulation affects the cells simply by inducing a local increase in temperature, which generates a localized increase in cellular metabolism.5
While this is interesting, it does not account for the significant increase in proliferation and in healing rates in comparison with other heating modalities. Numerous studies have focused on localized warming of the wound area with results that were not as impressive as those with electric stimulation.
Another theory is that electric stimulation causes a change in pH in the wound area. While pH has become an area of research of late in wound care, not enough is known to be able to attribute the increase in healing to this reason.