E-Stimulation: An Effective Modality to Facilitate Wound Healing
- Wed, 5/9/12 - 10:04am
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Every action in the body, from the cellular level to the level of gross motor function, begins as an electrical impulse. Exogenously applied electrical energy is something any wound care clinician should consider using to augment what is already a function of natural healing. When it comes to chronic wounds, electrical stimulation (ES), one of several biophysical technologies, is known by those healthcare providers who employ its use to be one of the most cost effective, therapeutically efficacious tissue repair and wound healing accelerators in the industry today.1 By restoring the natural electrical potentials necessary for cellular activities that have become stalled, ES re-establishes and intensifies healing processes.2,3
There has been substantial research regarding the effects of ES on the cellular and physiological mechanisms that enhance wound closure and healing.4 This article does not attempt to describe the evidence in detail; rather, the authors summarize the overall effects of ES on chronic wounds in an effort to familiarize clinicians with this underused efficacious treatment modality.
Types of Electrical Current
There are three types of electrical current that assist in wound closure and healing: direct current (DC), alternating current, and pulsed current (PC). The majority of clinical trials using ES currents for wound healing have used PC delivered in either monophasic- or biphasic-pulsed waveforms, whereby current is delivered to the wound via a number of pulses per second (pps).
There are three variations of PC that have been reported to augment chronic wound closure and healing. They are:
• high-voltage monophasic-pulsed current, frequently referred to as hi-volt pulsed current (HVPC);
• low-voltage monophasic-pulsed current; and
• low-voltage biphasic-pulsed current (LVBPC).
LVBPC is employed in transcutaneous electrical nerve stimulation (TENS) devices, primarily for pain control.4
At present, HVPC is the current most supported by the evidence for wound healing and is most frequently used for this purpose in the US. HVPC devices provide choices for polarity and pulsed frequency, which are known to affect cell behavior in and near the wound bed.4
ES Action on Cells and Tissue
Chronic wounds become stalled somewhere between the inflammatory and proliferative phases, often requiring assistance to restore the wound to the beginning of the inflammatory phase (so as to proceed through the proliferative phase and on to the maturation phase). Functioning cells are required for granulation tissue formation, wound closure, and subsequent healing through the maturation phase. Neutrophils and macrophages clean the wound and help decrease bioburden to prevent infection. Fibroblasts are the “workhorse” cells that build granulation tissue, and keratinocytes resurface the wounds. Early in vitro studies4-8 suggested cells involved in wound healing have their own inherent charge, and thus would be attracted to a treatment electrode having opposite polarity. More recent research has shown the motility of cells involved in wound healing can be enhanced by exogenously applied electrical fields; however, cell migration is not influenced in the same way that a charged particle (ion) is affected by electrical forces (Table 1).4,9
(For a sample of devices that deliver HVPC applicable for wound healing, visit www.todayswoundclinic.com beginning May 9. Note: This is a small sample and is not intended to be comprehensive regarding the devices available for sale and use.) Tables 2 and 3 describe the effects of ES on wound closure and healing, and the types of wounds that may benefit from ES application, respectively.
Using ES for Wound Closure4
Although several factors appear to affect cell movement in the wound bed using electrical currents, the choice of the polarity of the wound treatment electrode should be based on reports from clinical outcomes and best practice.
When using ES, the clinician introduces the current into or near the wound by setting the parameters on the device to facilitate the outcomes desired. Many ES device manufacturers preset some of these parameters to simplify treatment application. The following suggestions relate to parameter selection:
• Pulse frequency: 100 pps.
• Pulse duration: 20-100 µsec (usually fixed by the manufacturer).