Electrical Stimulation Therapy and Wound Healing: Where Are We Now?

Abstract

Background: Healing chronic wounds is an ongoing challenge for clinicians and poses a serious public health burden. Electrical stimulation (ES), broadly defined as the application of electrical current via electrodes placed on the skin adjacent to or directly within the wound, has been proposed as a therapeutic modality over a century ago, and recent advances in understanding the biology of electrical phenomena in the skin have rekindled an interest in this modality.

The problem: Despite evidence that has shown ES to be effective for wound healing, it has been slow to gain acceptance in the United States. Also, there has been no consensus in terms of standardization of parameters to devise a systematic protocol for implementation of this technology.

Basic/clinical science advances: The epidermis maintains a "skin battery" that generates an endogenous electric field and current flow when wounded. Experimental models have demonstrated that most of the cell types within the wound can sense an electric field in the range of that endogenously generated in the wound, and respond with a variety of biological and functional responses that can contribute to healing. Multiple animal wound models have demonstrated enhancement of a number of parameters of healing when ES is exogenously supplied.

Clinical care relevance: Clinical trials have investigated the efficacy of multiple forms of ES for improving healing in a wide variety of human chronic wounds. In 2002 the Centers for Medicare and Medicaid Services approved reimbursement for use of ES in a clinical setting for certain chronic wounds.

Conclusion: THERE REMAIN MANY VOIDS IN OUR KNOWLEDGE BASE: clinical evidence is limited by deficiencies in the design of many of the trials, a multiplicity of ES application modes and waveforms used in trials prevent selection of an optimal modality, and lack of uniformity in reporting ES dosages leave us not much advanced from our clinical knowledge base a decade ago.

Sara Dahle

Figure 1.

Generation of skin wound electric fields. Unbroken skin maintains a “skin battery,” derived by apical-basal transport of Na⁺ and generation of a transepithelial potential (A). When wounded, the potential drives current flow through the newly formed low-resistance pathway (B), generating an electric field whose negative vector points toward the wound center at the lower portion of the epidermis. Color images available online at www.liebertpub.com/wound

Figure 2.

Electrical stimulation devices used for healing chronic wounds. Devices used in the target studies: (A) Houghton et al.—the Micro Z^©, a portable monophasic twin peak wave form with high-voltage pulsed current and electroconductive sock (monopolar or bipolar method used). Voltage ranges from 50 to 150 V (www.advancedtherapyconcepts.com); (B) Lee et al.—the Electro Pressure Regeneration Therapy™ (EPRT) device, an ultra-low microcurrent that delivers square wave bipolar, direct current. Voltage ranges from 5 to 40 V (www.bodiharmoni.com); (C) Petrofsky et al.—customized three-channel stimulator, biphasic wave with 20 mA, and two pathways of current created rotated every second in sequence. Internationally available marketed devices: (D) Posifect^® by BIOFiSica (UK) Ltd., used in the United Kingdom, is a bandage that delivers direct current microamps with embedded metallic anode in outer and inner bandages with embedded metallic anode in a hydrogel placed over the wound; external power source required (www.sumed.co.uk); (E) Wound EL^® by GerroMed Dressing electrode and dispersing electrode, with patient-programmable external power source, delivers pulsed direct current stimulation; (F) Procellera^® by Vomaris, Inc., is the only U.S. FDA 510 K, over-the-counter, or by prescription approved medical device for partial and full-thickness wounds. A small voltage (2–10 mV) is produced by microbatteries of Ag and Zn metals printed onto woven bandage activated by moisture of the wound (http://procellera.com). Color images available online at www.liebertpub.com/wound