Health benefits related to the application of electrical current to biologic tissue were first documented in ancient Rome where currents generated by torpedo fish were used to treat chronic pain.^1,2 It is reported that the use of electricity as a medical intervention started when a freed slave accidently stepped on a torpedo fish and received an electric shock. The shock apparently “cured” the man of chronic pain associated with what is now believed to have been gout.² Since that time, electrical stimulation (ES) or “e-stim” technology has been utilized in both diagnostic and treatment procedures in multiple areas of patient care including general medicine, cardiology, surgery, and physical therapy.^1,2 General indications include electrocautery of bleeding vessels, muscle stimulation/reeducation, pain control, improved blood flow, and the transcutaneous delivery of medications.^1,3,4 Literature also documents that ES promotes wound healing by creating changes in epidermal polarity,⁵ cellular migration and function, blood flow, edema, and wound contraction,^6–8 as well as by decreasing bioburden and improving autolysis.⁵ Meta-analysis review confirms that through these changes, ES can increase wound healing by as much as 22% per week.^9,10 ES for wound healing is supported by multiple health professional organizations including the National Pressure Ulcer Advisory Panel, the European Pressure Ulcer Advisory Panel,^11,12 the Wound, Ostomy and Continence Nurses Society,¹³ and the American Physical Therapy Association’s Academy of Clinical Electrophysiology and Wound Management.¹⁴

This chapter discusses the therapeutic application of electrical current for wound healing using terminology presented in TABLE 14-1. ES equipment consists of an electric or battery-powered base unit with adjustments for parameters (eg, voltage, polarity, treatment time), electrodes that conform to the wound or periwound surface, and lead wires that connect electrodes to the base unit. Although no ES device is approved by the FDA specifically for wound management,¹⁵ general units that are used “off label” are of various sizes ranging from bulky, box-type units that can provide a variety of current types to small, handheld units designed for portability. TABLE 14-2 provides a partial list of ES vendors (FIGURES 14-1 and 14-2). Electrodes used for wound management include self-adhesive gel, carbon, and aluminum foil paired with an alligator clip and saline moistened gauze (FIGURE 14-3A–C). Lead wires, typically used in pairs, are available as single or bifurcated leads (FIGURE 14-4). CASE STUDY

INTRODUCTION

Mr DY is a 59-year-old male with a history of type 2 diabetes, renal insufficiency, and hypertension who presents with a non-healing wound on the plantar medial foot of more than 1-year duration. The wound began as a thick callus and progressed to necrotic tissue with underlying infection (FIGURE 14-5). He had surgical debridement about 1 month ago and has been treated with wet-to-dry dressings at home since then. He works for the state department and is currently out on disability.

FIGURE 14-5

Case study Wound on the left plantar foot of a patient who has a diabetic foot wound that has not responded to standard of care for 30 days. HVPC, 100 pps, 120 V, alternating active electrode with the direct method, for 45 minutes was applied twice a week.

DISCUSSION QUESTIONS

1. 
   

   What subjective information is needed to determine treatment for this patient?

   
   
2. 
   

   What objective tests and measures are advised before initiating treatment?

   
   
3. 
   

   What would be considered standard care for this type of wound?

Healthy, intact skin has a variable negative charge of approximately 23 mV, referred to as the transepithelial potential difference.^6,16 When a break in the skin occurs, the influx of positive charge (Na⁺) from the wound tissue and deeper layers of the epidermis interact with the negative charge (Cl⁻) of adjacent intact skin creating a low-level bioelectric signal to the body that an injury has occurred (FIGURE 14-6).^6,17,18 This endogenous signal, referred to as the current of injury,⁶ flows in a moist wound environment¹⁷ and continues to signal that repair is necessary until a new epidermis is established.¹⁹ This natural bioelectric signal for repair can be disrupted or halted with low tissue moisture, desiccation, or scab formation, thus resulting in reduced or stalled wound healing. Once a moist wound environment is reestablished, the application of an exogenous electrical current can mimic the normal current of injury, resulting in the attraction of key cells involved in tissue healing, and essentially reinitiating the healing process.^17,19

Additionally, through the action of electrotaxis (previously referred to as galvanotaxis),²⁰ ES positively affects wound healing by attracting cells necessary for healing into wounded tissue (FIGURE 14-7).²¹ Studies have shown that key cells involved in tissue healing, such as epithelial cells, fibroblasts, and macrophages, are attracted by electric charge (TABLE 14-3).²² In fact, recent studies support that electric charge is the “overriding guidance cue”²⁰ directing cell migration, and through this mechanism exogenously applied electrical current applied to a wound can facilitate an existing healing phase or encourage progression to the next phase of healing.²²

ES has been documented to have positive effects during all phases of tissue healing,^20–23 regardless of wound etiology, due to its ability to affect changes in cellular activity and migratory direction.²⁴ These specific cellular and tissue effects are presented in the following paragraphs and are organized by phase of wound healing. (Detailed descriptions of individual cell activity and role in wound healing can be reviewed in Chapter 2, Healing Response in Acute and Chronic Wounds.)

Inflammation

Primary cells active during the inflammatory phase include neutrophils and macrophages. Since both neutrophils and macrophages carry a negative charge, research supports that an exogenously applied electropositive field can encourage increased numbers of these cells to migrate into the wound bed,⁶ thereby facilitating the inflammatory process. Increased numbers of macrophages also facilitate debridement of nonviable tissue and wound debris. In the case of wound infection, activated neutrophils become positively charged²⁶; thus, application of negative polarity will encourage increased bacterial destruction and reduction in bioburden. Positively charged mast cells can also be repelled by exogenously applied electrical current, which may result in decreased tissue fibrosis over the course of tissue healing.^27–29

Proliferation

Positively charged fibroblasts are the primary cells active during the proliferation phase and are attracted by negative polarity. ES application during the proliferative phase has been shown to increase both the number and activity of fibroblasts, thereby increasing protein synthesis, collagen deposition,^6,26,30,31 and overall faster wound contraction.^7,21,22 ES also encourages increased blood flow³² to the wound and periwound tissue by facilitating increased capillary density^27,33 and inhibiting local vasoconstriction.³⁴ These effects may be further enhanced when ES is delivered in a warm (∼32°C) environment so that the risk of inducing vasoconstriction of the skin due to cool room temperatures is reduced.³⁵

Epithelialization

When positively charged electrical current is applied to a granulated wound, negatively charged epithelial cells increase their migratory distance, moving from the wound edge toward the center, and increase the speed at which they migrate across the wound surface. Epithelial cells increase their migratory distance and also increase the speed at which they migrate across the wound surface.³⁶ The application of therapeutic levels of electrical current does not disrupt cellular adhesion between epithelial cells,³⁷ and in fact, may actually augment the bonding or grouping of these cells,³⁸ thereby encouraging overall faster migration of large epithelial sheets across wound surfaces.³⁷

Remodeling and Maturation

When applied during the remodeling phase of healing, exogenously applied ES has been shown to reduce scar hypertrophy³⁹ while improving overall scar tensile strength.^7,21,22 These benefits are achieved through the application of positively charged electrical current, which repels like-charged mast cells in target tissues. CLINICAL CONSIDERATION

If a wound being treated with electrical stimulation appears to stall in the healing process, changing the polarity of the treatment may be beneficial. Sussman’s protocol recommended alternating every third day for proliferation and every day for epithelializaiton.⁶

Published literature regarding cellular and tissue effects supports the application of ES for most chronic wounds (TABLE 14-4).^{6,21,23,40,41} In fact, research so strongly supports the use of ES for chronic wounds that in 2002 the Centers for Medicare and Medicaid Services (CMS) announced ES coverage for arterial, venous, pressure, and diabetic wounds that have not responded to 30 days of standard treatment (TABLE 14-5).^25,26,41,42 ES may also be indicated for wounds that begin to demonstrate slow or stalled healing.¹⁷ CASE STUDY

The patient reports the following subjective information:

• 
  

  He is wearing an athletic shoe and walks 2–3 miles a day to help manage his diabetes.

  
  
• 
  

  Blood sugars are taken every morning and are usually between 120 and 160.

  
  
• 
  

  His medications include Glucophage, Norvasc, and Lasix.

  
  
• 
  

  He is currently working with his nephrologist to initiate peritoneal dialysis at home.

Objective information includes the following:

• 
  

  Wound size is 5.8 cm × 3.1 cm × 0.4 cm with 3–5 mm of undermining at the medial proximal edge.

  
  
• 
  

  Drainage is moderate, serosanguineous, and problematic for the patient in his current lifestyle.

  
  
• 
  

  Pulses are palpable and 2+ (both DP and PT).

  
  
• 
  

  There is positive response to 5.07 monofilament at the dorsal foot, negative response on the plantar foot.

  
  
• 
  

  Achilles tendon reflexes are diminished.

  
  
• 
  

  There is pitting edema on the lower extremity to the knee.

  
  
• 
  

  Gait is independent without assistive device; however, with wide base of support, minimal heel/toe sequence, and lateral trunk sway.

  
  
• 
  

  The patient can perform sit to stand without upper extremities, five times in 20 seconds.

  
  
• 
  

  The patient is unable to single-leg stance on either lower extremity.

  
  
• 
  

  Lower extremity strength is 4-/5; ankle range of motion is 5–30 degrees plantar flexion on the left, 5–40 on the right.

DISCUSSION QUESTIONS

1. 
   

   Is electrical stimulation an appropriate intervention for this patient?

   
   
2. 
   

   What would be the optimal off-loading strategy for this patient?

   
   
3. 
   

   What other physical therapy interventions (other than wound care) would be beneficial for overall function?

Kloth and McCulloch¹⁷ report that petrolatum or heavy metal–based dressings may interfere with the normal bioelectric nature of wound tissues; they need to be thoroughly cleansed from the wound prior to application of the ES. As mentioned previously, wound desiccation can also affect wound bioelectric currents. Once infection has been ruled out and dressing residue and moisture issues resolved, ES may be indicated to reestablish normal bioelectric currents in the wound and reinitiate the healing process.¹⁷