Pulsed electromagnetic field therapy: electrotherapy unplugged.
Pulsed electromagnetic field therapy grew out of the use of diathermy technologies about 100 years ago. In their original forms, diathermy devices generated short-wave radio waves that penetrated into tissue to generate therapeutic deep heat. By the mid-1930s, at least one clinician, a Dr. Ginsberg, saw enough differences in outcomes from using diathermy as compared with other forms of tissue heating that he eliminated the heating effects of diathermy by reducing the duty cycle of the machine to have it pulse in short bursts. The outcome was effective therapy for a variety of conditions without heating tissue. The technology was commercialized by the 1950s and became part of the therapeutic armamentarium in physical medicine, where it is still found today.
PEMF technology for bone growth stimulation grew out of a separate initiative. After the discovery, in the 1950s, that bone produced electrical currents when stressed, a number of researchers began to examine the utility of the electrical treatment of fractures as a means to healing them. By the late 1960s, non-healing fractures were being treated with direct electrical stimulation, not unlike that used today for pain and wound care treatment. The surgeon implanted electrodes on either side of a non-healing fracture and an external generator provided the current that often lead to bone healing. In the 1970s, an innovative electrochemist proposed that external pulsed electromagnetic fields could be used to induce an electric current in the bone, eliminating the need for surgically implanting electrodes, which carries a significant risk of infection. The notion that pulsed electromagnetic fields can cause electrical current to flow in a conductor (like bone or other human tissue) is just a basic characteristic of the properties of electromagnetism and is used widely, from hydroelectric power to household appliances. The application of that fact to bone growth stimulators made possible the ability to treat recalcitrant fractures externally, as the pulsed electromagnetic field treats directly through casts, dressings, clothing, etc. Patients themselves, once instructed on use, can use these systems easily. Simply place the lightweight applicator over the treatment area and turn on the power. The success rate of healing recalcitrant fractures is around 80%, the same success rate as a first surgical graft, but it does not carry any of the risks associated with surgery. Lastly, bone growth stimulators, like other PEMF technologies, have no-known adverse or side effects, and few restrictions on use.
In the end, both threads of history point to the possibility and then the utility of delivering electrotherapy through pulsed electromagnetic fields. As is well known in orthopedics, but not as well disseminated in other areas of practice, PEMF is only a delivery system for electrotherapy. Nothing about the electromagnetic field itself is therapeutic. The only therapeutic component is the electrical energy deposited in the tissue. While orthopedics made significant advances in the use of PEMF therapies, the rest of physical medicine continued to use direct electrical stimulation modalities for the most part. The only PEMF therapy technologies found in physical medicine were the older, pulsed diathermy technologies, which had significant constraints on use due to interference, as well as size and ergonomics. These products are generally characterized by a power supply and an applicator. These devices can produce up to 1,000 watts of energy, which can reduce the utility of the technology. Such high energy increases the probability of electromagnetic interference (EMI) with other kinds of electronic equipment, from telephones and radios to computers, PDAs, monitoring equipment and other clinically necessary equipment.
The other barrier to the development and adoption of PEMF therapies in the treatment of chronic wounds is the knowledge of electrical stimulation and the regulatory constraints that exist on marketing the technologies. The FDA usually clears electrotherapies for the treatment of pain and PEMF therapies for the treatment of pain and edema in soft tissue. Other uses, no matter how successful, are considered "off-label" and manufacturers do not advertise their products for such uses. So the amount of information available is reduced or indirect, impairing the clinician from easily finding pertinent information for uses, such as wound care. The knowledge base for the use of electrical stimulation, especially in the area of wound care, may be significant, but the number of practitioners is relatively low, partly because physical therapists do not do wound care in many settings and nurses, who do the bulk of wound care both in and out of institutions, do not have the specialized training available in physical therapy education. This means that many facilities do not have the expertise in modalities to even use available modalities, much less choose among competing modalities.
In the past several years, improved understanding of the mechanisms underlying PEMF technology has advanced the technology, leading to improved design and utility of PEMF in soft tissue. Pilla has written a comprehensive review of the PEMF literature. (1) Recent animal studies illustrate the different physiological effects of PEMF signals. (2) Newer, targeted PEMF technology is designed to specifically affect well-known physiological processes. Targeted PEMF is designed to accelerate the normal anti-inflammatory activity of the body. Multiple, sometimes concurrent, biological activities take place from the initial pain and swelling, through new blood vessel formation (angiogenesis) to tissue regeneration and then tissue remodeling. These processes are all related to an initial step, so accelerating that first electrochemical process should accelerate the whole cascade. Tissues will respond depending on their current state, so acutely inflamed tissue should rapidly respond by reductions in pain and swelling, while chronic wounds, for example, should see improvements in blood flow and growth factor production. (3,4,5)
The practical aspects of this advance in targeting PEMF to differentially affect specific electrochemical processes is significant reductions in power needs, and therefore size, weight, and electromagnetic interference. Currently available targeted PEMF technologies can be found in lightweight, battery operated, and disposable products and in institutional products that are virtually free from electromagnetic interference and can treat multiple sites on a patient simultaneously with lightweight applicators. The institutional technology can be used in electrically intensive environments, such as in LTACHs and ICUs, without interference. This allows for a much more versatile use of the technology. The disposable technology can be pre-programmed to provide a course of treatment for a week or more without any user intervention. The products can be placed over dressings and activated. These products can remain in place for up to two weeks; when the dressings are changed (the frequency depending on the type of dressing), the product is just reapplied over the new dressing. As more and more patients move from institutional settings and into their homes, technologies that can follow them may offer superior outcomes.
PEMF and other electrotherapies have some history in the off-label use with chronic wounds. As far back as 1994, the AHCPR guidelines endorsed only electrotherapies as having sufficient evidence to warrant recommendation. The evidence has continued to accrue, leading to Medicare's National Coverage Determination for the use of electrotherapy and PEMF in the treatment of chronic wounds (stage III and stage IV pressure ulcers, arterial, venous stasis and diabetic ulcers) under the HCPCS code G0329. (6,7) Currently, PEMF is subject to a National Coverage Determination by CMS for the treatment of chronic wounds.
The critical understanding is that PEMF, even targeted PEMF, is only a delivery system for an electrotherapy. However, unlike other forms of electrotherapy delivery, PEMF will treat directly through dressings, casts, and clothing. Because a PEMF devices produces a homogenous electrical field, it is omni-directional (not dependent on electrode placement), and can be used with virtually any other wound care therapy, e.g, HBO, advanced wound dressings, negative pressure wound therapy, without altering current practice. The following case studies, from my practice, illustrate the capabilities of the technology, in conjunction with an excellent outpatient wound care program.
These cases are drawn from an underserved, Native American population, mostly in rural settings. Approximately 3.3 million Native Americans live in the US. Their disease burden greatly exceeds national averages, with 5 times the tuberculosis, twice the incidence of diabetes, and a significant number of chronic wounds being under-treated. Technologies that can be incorporated into current wound care practice, can stay in place, and can eliminate compliance problems through automatic treatment regimens may help overcome some of the existing hurdles to effective treatment. Targeted PEMF provides this combination of characteristics and was piloted on a variety of cases, illustrated below. In all the cases, the patients were provided with disposable products that provided an automatic treatment regimen (Ivivi Technologies, Montvale, NJ) and were replaced weekly when the patients visited their wound care clinics.
This patient had a failed abdominal closure; she was being cared for in a small, rural wound care clinic. This 61 y.o. woman was obese, diabetic, and had peripheral arterial disease. She had abdominal surgery and then two further surgeries after becoming septic. She was hospitalized for over 3 months before coming to the wound clinic. The initial assessment by the surgeon was a 9-18 month healing timeline. Figure 1 shows the wound prior to using targeted PEMF and figure 2 shows healing at 25 days. Complete healing occurred by day 38.
This patient had significant comorbidities and compliance issues that prevented successful closure of his long-standing wounds. He was 55 y.o. man with poorly controlled diabetes, liver impairment, and severe peripheral arterial disease. His history was significant for overweight and alcohol abuse. His job as a security guard required walking. This patient was able to continue work with compression and appropriate dressings for drainage (Unna's boots twice a week). Figure 3 shows this wound, which had been open for 10 months at the initiation of PEMF therapy. Figure 4 shows healed wounds at 12 weeks.
The final case illustrates the significant diversity of wounds found in this population, as well as demonstrating how the technology can be incorporated directly into a dressing. This 48 y.o. man had an infection secondary to a tick bite in 1987, which led to stripping and debulking surgery of the lymph system in that leg in 2002. The patient developed ulcers on that ankle secondary to compression dressings. The wounds did not progress for 5 months, while the leg gained 4 inches in diameter due to edema. Figure 5 shows the limb. An open wound is bandaged. Figure 6 shows the PEMF product in place over the offloading appliance and dressings. This leg lost 2 inches of diameter with two weeks of treatment and looked remarkably better, with visibly better perfusion and noticeably less drainage. Over the course of 6 weeks, the patient lost another 1.25 inches in diameter to the leg, was able to wash and care for his leg, and the oozing ceased completely.
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Electrotherapies have long been recognized as effective adjuncts in the treatment of chronic wounds. Recently, Medicare has recognized PEMF as an effective delivery system for electrotherapy. It is vastly simpler to use, paralleling the evolution of bone growth stimulators, 25 years later. The targeted PEMF therapy currently available provides a lower-cost, high-compliance technology that offers the benefits of electrotherapy without any of the associated challenges.
(1.) Pilla A. 2006. Mechanisms and 1. therapeutic applications for timevarying and static magnetic fields. In: Handbook of Biological Effects of Electromagnetic Fields, 3rd Edition. Barnes, F. and Greenbaum, B., Eds. CRC Press.
(2.) Strauch B, Patel M, Rosen D, et al. A 2. pulsed magnetic field therapy increases tensile strength in a rat Achilles tendon repair model. J Hand Surg 2006;31A: 1131-1135
(3.) Roland D, Ferder M, Kothuru R, et al. 3. Effects of pulsed magnetic energy on a micro surgically transferred vessel. Plast Reconstr Surg 2000;105:1371-1374.
(4.) Weber RV, Navarro JA, Wu JK, et al. 4. Pulsed magnetic energy (PME) applied to a transferred arterial loop supports the rat groin composite flap. Plast Reconstr Surg 2004;114:1185-1189.
(5.) Tepper OM, Callaghan MJ, Chang EI, 5. et al. Electromagnetic fields increase in vitro and in vivo angiogenesis through endothelial release of FGF-2. FASEB 2004;18:1231-1233.
(6.) CMS. Decision Memo for 6. Electrostimulation for Wounds (CAG-00068R), 2003. http:// www.cms.hhs.gov/mccd/viewdecisionmemo.asp?id=28. Last Accessed January 2008.
(7.) Ojingwa, J., and Isseroff, R. 2002. Electrical Stimulation of 7. Wound Healing. Journal of Investigative Dermatology. 36: 1-12.
Patricia Justice-Stevenson, RN, BSN, CWS
Patricia Justice-Stevenson, RN, BSN, CWS is Director Clinical Services, Advanced Wound Care Services, LLC. Her practice is focused on developing evidence-based outpatient wound care programs in small rural health care facilities. Contact at: firstname.lastname@example.org