High volt 03

Effect of Electrical Stimulation onChronic Leg Ulcer Size andAppearance

Background and Purpose. Electrical current has been recommendedfor use on chronic pressure ulcers; however, the ability of this modalityto improve healing of other types of chronic ulcers is less wellestablished. The purpose of this study was to examine the effect ofhigh-voltage pulsed current (HVPC) on healing of chronic leg ulcers.Subjects. Twenty-seven people with 42 chronic leg ulcers participatedin the study. Methods. The subjects were separated into subgroupsaccording to primary etiology of the wound (diabetes, arterial insuffi-ciency, venous insufficiency) and then randomly assigned to receiveeither HVPC (100 microseconds, 150 V, 100 Hz) or a sham treatmentfor 45 minutes, 3 times weekly, for 4 weeks. Wound surface area andwound appearance were assessed during an initial examination, fol-lowing a 1- to 2-week period during which subjects received onlyconventional wound therapy, after 4 weeks of sham or HVPC treat-ment, and at 1 month following treatments. Results. The resultsindicated that HVPC applied to chronic leg ulcers reduced the woundsurface area over the 4-week treatment period to approximately onehalf the initial wound size (mean decrease�44.3%, SD�8.8%,range�2.8%-100%), which was over 2 times greater than that observedin wounds treated with sham units (mean decrease�16.0%, SD�8.9%,range��30.3%-83.7%). Discussion and Conclusion. The results of thestudy indicate that HVPC administered 3 times a week should beconsidered to accelerate wound closure of chronic leg ulcers. [Hough-ton PE, Kincaid CB, Lovell M, et al. Effect of electrical stimulation onchronic leg ulcer size and appearance. Phys Ther. 2003;83;17–28.]

Key Words: Acetate tracings, Chronic ulcers, Diabetic foot ulcers, Electrical stimulation, Photographic

Wound Assessment Tool (PWAT), Venous leg ulcers, Wound size and appearance.

Pamela E Houghton, Cynthia B Kincaid, Marge Lovell, Karen E Campbell, David H Keast, M GailWoodbury, Kenneth A Harris

Physical Therapy . Volume 83 . Number 1 . January 2003 17

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Chronic vascular leg ulcers due to venous insuffi-ciency, atherosclerosis, diabetes mellitus, orsmall vessel disease affect approximately 1% ofthe general population and up to 10% of indi-

viduals who are in health care facilities.1 Slow-healingvascular ulcers have serious human consequences,including pain, lost workdays, and marked reduction inquality of life.2 Furthermore, 70% to 90% of leg ampu-tations are due to vascular ulcers, and foot ulcerationand infection are leading causes of hospitalizationamong people with peripheral vascular disease due todiabetes mellitus.3 Chronic ulcers due to venous insuffi-ciency represent approximately 70% to 90% of chroniclower-extremity ulcers. Costs associated with the manage-ment of these ulcers on an outpatient basis in the UnitedStates have been as high as $2,500 per ulcer for a4-month period.4 Given that many of the factors thatpredispose individuals to develop chronic wounds aremore prevalent with advancing age, the human andfinancial costs of assessing and managing this problem

are likely to rise significantly as the average age of theNorth American population increases.

Researchers have begun to examine the efficacy ofvarious therapeutic approaches designed to acceleratewound healing.5,6 A therapeutic approach that acceler-ates wound closure could reduce health care costs.Several putative therapeutic approaches have been pro-posed, including the use of antiseptics, antibiotics,growth factors, pressurized oxygen, biologically engi-neered skin substitutes, and physical therapy modalitiessuch as electrical stimulation.

Numerous reports7–21 support the use of electrical stim-ulation for managing chronic wounds. In randomizedcontrolled clinical trials,7,8,15,17,19,21 electrical stimulationhas been shown to improve the healing rates of chronicpressure ulcers occurring with limited mobility or lim-ited cognitive ability because of conditions such as spinalcord injury, stroke, or brain trauma.

PE Houghton, BScPT, PhD, is Associate Professor, School of Physical Therapy, University of Western Ontario, Room 1443, London, Ontario,Canada N6G 1H1 ([email protected]). Address all correspondence to Dr Houghton.

CB Kincaid, PT, MEd, is Associate Director for Clinical Education and Clinical Associate Professor, Department of Physical Therapy, University ofMichigan–Flint, Flint, Mich.

M Lovell, RN, is Clinical Research Nurse, Vascular Service, Victoria Campus, London Health Science Centre, London, Ontario, Canada.

KE Campbell, NP/CNS, RN, MScN, is Clinical Nurse Specialist, Wound Care, Parkwood Hospital, St Joseph’s Health Care London, London,Ontario, Canada.

DH Keast, MD, FCFP, is Medical Director, Interdisciplinary Wound Management Clinic, Parkwood Hospital, St Joseph’s Health Care London, andFamily Physician, London, Ontario, Canada.

MG Woodbury, BScPT, PhD, is Epidemiologist, Research Department, Parkwood Hospital, St Joseph’s Health Care London, and AdjunctProfessor, Department of Biostatistics and Epidemiology, University of Western Ontario.

KA Harris, MD, FRCSC, FACS, is Vascular Surgeon, Victoria Campus, London Health Sciences Centre, London, Ontario, Canada, and Chair,Department of Surgery, Faculty of Medicine, University of Western Ontario.

Dr Houghton and Ms Kincaid provided concept/idea/research design. Dr Houghton provided writing and project management, and DrHoughton and Ms Lovell provided data collection. Dr Woodbury provided data analysis and consultation (including review of manuscript beforesubmission). Ms Campbell, Dr Harris, and Dr Keast provided fund procurement, subjects, facilities/equipment, and institutional liaisons. Theauthors acknowledge the following students enrolled in the undergraduate program in physical therapy at the University of Western Ontario fortheir invaluable contributions to this research project: Leya DeBryn, Michelle Allin, Anna Banks, Jeannie Tschirart, Megan Close, Jada Close, andGeorge Paradalis were involved in administering weekly treatment sessions; Lisa Morrison played a key role in establishing documentation skillsand reliable outcome measures; and Beth Desveaux, Donovan Stewart, and Linh Nyugen performed the data analysis of wound surface areas andthe calculation of wound appearance scores.

Study approval was obtained from the Review Board for Health Sciences Research Involving Human Subjects at the University of Western Ontarioand from the Research Committee at Parkwood Hospital of St Joseph’s Health Care London and the Clinical Research Investigation Committeeat Victoria Campus of London Health Sciences Centre.

This research was performed at the University of Western Ontario with support from a grant obtained by Brenda O’Neill from The VictoriaHospital Foundation, London Health Sciences Centre. Equipment used in the study was supplied by Electro-Med Health Industries, North Miami,Fla.

This article was submitted December 6, 2001, and was accepted July 26, 2002.

18 . Houghton et al Physical Therapy . Volume 83 . Number 1 . January 2003

Using this research, the US Department of Health andHuman Services’ Agency for Healthcare Research andQuality (AHRQ) (formerly the Agency for Health CarePolicy and Research [AHCPR]) developed and pub-lished clinical practice guidelines for the managementof pressure ulcers.22 The guidelines state that “electricalstimulation is the only adjunctive therapy with sufficientsupporting evidence to warrant recommendation by thepanel,”22(p55) to be used for enhancing the healing rateof stage II or III pressure ulcers that have been unre-sponsive to conventional therapy. The evidence for theuse of electrical simulation for chronic pressure ulcerswas revisited in a 1998 review of the research literatureperformed by Dr Liza Ovington.23 Based on this morerecent review of the research literature, she suggestedthat the strength of evidence rating should be upgradedto the highest rating possible (rating of A � positiveresults exists from 2 or more randomized controlledclinical trials).

Despite the strong evidence supporting the use of elec-trical stimulation for chronic wounds, most research hasexamined the effect of this modality on either pressureulcers7–16 or ulcers due to mixed etiologies.17–21 Fewresearchers have examined the effectiveness of electricalstimulation for chronic wounds due to other etiologiessuch as venous and arterial insufficiency.24–29 Therefore,the purpose of our study was to examine the effect ofHVPC on wound healing of chronic lower-extremityulcers due to diabetes or to arterial or venousinsufficiency.

Method

Subject RecruitmentIndividuals with at least one lower-extremity chronicwound lasting longer than 3 months were recruited intothe study via advertisements in local media and throughcollaboration with physicians and wound care specialistsserving either outpatient clinics or an inpatient popula-tion. Individuals who agreed to participate in the studysigned an informed consent statement and then werescreened using inclusion and exclusion criteria asapproved by local institutional review boards. The inclu-sion criteria were: (1) the individual had one or morefull-thickness skin ulcers located below the knee ofgreater than 3 months’ duration; (2) the primary etiol-ogy of the wound was either venous or arterial insuffi-ciency, or the wound was due to diabetes mellitus; and(3) the individual had received medical attention for themedical condition believed to be the primary cause ofthe wound that included appropriate standardizedwound care and nutritional information.

Subjects were excluded from the study if they wereundergoing corticosteroid therapy, radiation therapy, or

chemotherapy for cancer, all of which would interferewith the ability to heal. Other exclusion criteria includedany of the following medical conditions for which elec-trical stimulation is contraindicated5: (1) ventriculararrhythmia, (2) atrial fibrillation, (3) use of a cardiacpacemaker, (4) history of deep radiation therapy withinthe local region, (5) known deep venous thrombosis orthrombophlebitis, (6) superficial metal ions or metalimplants near the area, (7) pregnancy, or (8) activeosteomyelitis.

Subject DemographicsA total of 33 individuals volunteered to participate in thestudy. Four subjects did not meet the inclusion andexclusion criteria, and 2 subjects did not complete the4-week treatment program. Both of these subjects hadbeen assigned to a group who received a sham treat-ment. They elected to withdraw from the study forreasons unrelated to the treatment. A total of 27 peoplewith 42 ulcers completed the study protocol.

Demographic information on the subjects enrolled inthe study was obtained from a standardized subjectinterview, physical examination, vascular flow laboratorysession, or medical chart review (Tab. 1). Subjects wererandomly assigned to either a group who received HVPC(n�14) or a group who received sham HVPC (n�13)(see “Study Design” section). A similar number of femalesubjects were present in each treatment group. Theaverage ages of the subjects were 66.3 years (SD�4.8,range�25–91) for the subjects who received HVPC and62.4 years (SD�5.6, range�31–81) for the subjects whoreceived the sham treatment. The mean duration oftime the subjects had their ulcers prior to entry into theprogram was 2.96 years (SD�1.4, range�0.8–15) for thesubjects who received HVPC and 5.47 years (SD�2.4,range�0.25–25) for the subjects who received the shamtreatment. The relatively high value for the mean dura-tion of ulcer in the sham treatment group was due to onesubject in this group who had an ulcer that had beenpresent for 25 years. Nineteen out of 27 ulcers werelocated in the ankle or malleolar region of the leg, withall ulcers under study located below the level of theknee. Approximately half of the ulcers in the study werevenous ulcers. Arterial ulcers represented the type ofulcer present in fewest number of subjects in the study(n�2). Three subjects in each treatment group haddiabetes and venous insufficiency or arterial disease.

Initial ExaminationRelevant information about the history and severity ofany medical conditions known to influence wound heal-ing were determined using a questionnaire and wereverified by use of a medical chart review. After obtainingthe relevant medical history, both limbs were observedand any signs of vascular insufficiency were noted. These

Physical Therapy . Volume 83 . Number 1 . January 2003 Houghton et al . 19

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observations included the presence of pale, shiny, skin,thickened nails, little hair growth, cool skin tempera-ture, weak or absent foot pulses, and the presence ofvaricosities or visual identification of skin stained withdark brown hemosiderin pigment, or bilateral limbswelling or lymphedema.30 A small blood sample wasobtained and analyzed using a glucose monitor (OneTouch Blood Glucose Monitoring System*) to identifysubjects with hyperglycemia. A calibrated nylon 5.07Semmes-Weinstein monofilament was applied with suffi-

cient pressure to produce filament bending to 10 pre-determined locations of the plantar aspect of the sub-jects’ feet in a random cadence and order. Resultsobtained using these monofilaments vary little and thatfilaments produce a controlled reproducible force of10 g.31 People who are unable to detect this monofila-ment have a higher risk of foot ulceration and areconsidered to lack the protective sensation necessary todetect and respond to excessive external pressure.32

The relative amount pain associated with the wound wasassessed prior to manipulating the wound in any wayusing a well-established visual analog scale. The reliabil-* Lifescan Canada Ltd, 300-4170 Creek Dr, Burnaby, British Columbia, Canada

V5C 6C6.

Table 1.Patient Demographics and Coexisting Medical Conditions Determined in Initial Evaluation

Factor AffectingHealing

Subjects Who ReceivedHVPCa (n�14)

Subjects Who ReceivedSham Treatment (n�13)

Sex 5 female/9 male 5 female/8 male

Age (y)X 66.3 62.4SD 4.8 5.6Range 25–91 31–81

Duration (y)X 2.96 4.57SD 1.4 2.4Range 0.8–15 0.25–25

Initial wound size (cm2)X 6.39 5.53SD 1.85 1.96Range 0.24–38.1 0.24–29.8

Ankle brachial indexX 0.85 0.89SD 0.1 0.1

Blood glucose concentration (mmol)X 6.53 8.81SD 0.9 1.8

(4 subjects �10 mmol) (5 subjects �10 mmol)

Visual analog scale pain score (mm)X 1.48 1.16SD 0.6 0.6

Sensory impairment (no. of subjects in group) 6 7

Infected wounds (n) 8 4

Wound locationToe 2 1Foot 2 2Ankle/malleolus 6 7Leg 4 2

Type of ulcerDiabetic 2 3Arterial 2 0Venous 7 6Mixed 3 3

No. of factors affecting wound healing per subjectX 4.85 4.91SD 0.5 0.9

a HVPC�high-voltage pulsed current.


ity of results obtained on initial and repeated assess-ments of an individual’s pain is considered excellent(r �.95).33 This pain assessment involved asking thesubjects to indicate their level of pain on a 100-mm linemarked at one end with the descriptor “worst pain” andat the other end with the descriptor “no pain.” We alsonoted the presence of signs of infection, including apositive swab culture, marked redness extending beyondwound margins, increased pain, and foul-smelling puru-lent wound exudate.

Information gained during this interview was used todocument the number and type of medical conditionsknown to affect wound healing that were present in thesubjects such as chronic obstructive pulmonary disease,congestive heart failure, or coronary artery disease. Theobservations from this initial examination together withresults from Doppler ultrasound studies performed in avascular flow laboratory also were used to determine theprimary etiology of the wound (diabetic, arterial, orvenous). Subjects were considered to have diabetes ifthey had a blood glucose concentration within the last24 hours that was greater than 10 mmol (180 mg/dL).We considered arterial insufficiency to be present if theDoppler ultrasound recorded an ankle brachial pressureindex of less than 0.8, a value commonly used todesignate the presence of moderate arterial insufficien-cy.34 We considered venous insufficiency to be present ifa subject had varicosities, gravity-dependent leg edemaor lipodermatosclerosis, or hemosiderin staining of thelower extremity.35

Eight subjects who received HVPC and 4 subjects whoreceived the sham treatment had signs of infection at thetime of the initial examination and were prescribedappropriate antimicrobial therapy. A similar number ofsubjects in each group were unable to accurately detecta 10-g Semmes-Weinstein monofilament and thus wereconsidered to have lack a protective sensory response.32

Based on the initial evaluation, we counted the numberof factors known to affect wound healing for eachsubject. On average, the subjects in each group had 5 ofthese factors known to affect wound healing. On thebasis of these descriptive data, we believe that oursubjects represented a relatively broad heterogeneoussubject population of individuals who typically havechronic leg wounds.

Comparing the frequency of each of these factors knownto affect healing between treatment groups using aMann-Whitney rank sum test revealed that none of thesedescriptive variables were different between treatmentgroups. Mean values for age, duration of the ulcer, initialwound size, ankle brachial index, mean pain score, andblood glucose concentration were compared for subjectsin each treatment group using the Student t test. We

found that the mean values for each of these factorsknown to affect wound healing were not differentbetween the 2 treatment groups.

Pearson product moment correlation coefficients werecalculated to examine the correlation between subjectdemographics, coexisting medical conditions, and con-current therapies with the change in wound size thatoccurred over the study period. Wound healing, consid-ered as a reduction in wound size, that occurred over thestudy period in the subjects in either treatment groupwas negatively correlated with duration of ulcer(r �.547), blood glucose concentration greater than 10mmol (r �.345), and the number of factors affectingwound healing (r �.409). These correlations were notstatistically significant.

Study DesignWe designed the study to be a randomized, double-blind, prospective clinical trial. Subjects satisfying theinclusion and exclusion criteria were divided into 3subgroups based on predetermined criteria according tothe primary etiology of the wound (diabetes, arterialinsufficiency, venous insufficiency). The subjects thenwere randomly assigned to either group A or group B.Both groups of subjects were treated identically usingelectrical stimulators (EGS Model 300 electrical stimula-tors†) that were marked “A” or “B.” The equipment usedon the subjects who received the sham treatment hadbeen deactivated by the manufacturer in an inconspicu-ous manner so that neither the subjects nor theresearcher were aware of which group of subjects werereceiving real or sham treatment. Some of the subjects(n�11) were admitted to the study with more than onewound. Two of these subjects developed a new ulcer thatdid not resolve with standard wound care over a 3-monthperiod and were readmitted to the study. Nine of thesesubjects had bilateral ulcers seven of which were venousleg ulcers. In all these cases one ulcer was randomlyselected to be treated with a electrical stimulator marked“A,” and the other ulcer was treated with an electricalstimulator marked “B.” At the completion of the study,when all the data had been collected and analyzed, it wasrevealed that electrical stimulators marked “A” wereactive and those marked “B” had been deactivated.

Subjects enrolled in the study were told during the initialtreatment session that although they could expect somediscomfort during procedures involved in removing thedressing, cleansing the wound, and placing the activeelectrode in the wound, they should not experience painduring the course of the 45-minute treatment period.Subjects were told that if they were to feel any discomfort

† Electro-Med Health Industries, 11601 Biscayne Blvd, Ste 200A, North Miami, FL33181.


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during the treatment, they should inform the therapist,who would adjust the stimulator. No subject in eithertreatment group reported any discomfort during a treat-ment session, and no adverse reactions following treat-ment sessions were recorded during the course of thestudy.

Standard Wound CareTable 2 presents information on concurrent interven-tions also administered during the study. These interven-tions included pressure relief and protection for individ-uals with sensory impairment and compression therapyfor persistent leg edema. Wound dressings used in thestudy included nonadherent gauze pads, hydrogels,hydrocolloids, and absorbent foam dressings. Dressingssuspected of adversely interacting with electrical stimu-lation, such as topical agents with metal ions andpetrolatum-based products, were not prescribed. A stan-dardized dressing protocol was not used in this study;rather, dressings were tailored to meet the needs of eachsubject and to promote moist interactive healing.Wound dressings were changed if the wound was eithermacerated or dessicated. In most cases, the wounddressing used by the patient before enrolling in the studywas continued throughout the treatment period.

Sharp debridement procedures were performed, asneeded, by qualified personnel in a relatively smallnumber of subjects in each treatment group (n�4 andn�5). These procedures were done most often on asingle occasion during the a 1- to 2-week period duringwhich subjects received only conventional wound ther-apy and involved primarily the removal of excess callusformed around foot ulcers. When we believed infectionmight be present, the subject’s attending physician wascontacted and oral antibiotic therapy was initiated whereindicated. These concurrent interventions were usedconsistently throughout the treatment program andwere applied similarly for subjects in both treatmentgroups. In addition, subjects were asked to rate their

ability to adhere to the standard woundcare program during the 4-week treat-ment period. Very few individualsenrolled in the study did not carry outall of the necessary interventions, andthe number of subjects who wereunable to adhere to the wound careprogram was similar in both treatmentgroups (n�3).

Treatment SessionFollowing the 1- to 2-week period dur-ing which subjects received only con-ventional wound therapy, all subjectswere treated for 45 minutes with eitherreal or sham electrical stimulation 3

times a week for 4 weeks. The active electrode made ofMetalline gauze‡ was secured directly over the wound,which previously had been loosely packed with sterilegauze soaked in isotonic saline. A second dispersiveelectrode was placed approximately 20 cm proximal tothe wound. A portable high-voltage pulsed galvanicstimulator† supplied by Electro-Med Health Industrieswas used to deliver the electrical stimulus. Because thisstimulator is a battery-operated unit, the batteries wererecharged regularly at the beginning of each week oftreatment. The following settings were used: pulse dura-tion � 100 microseconds, peak intensity � 150 V, andpulse frequency � 100 Hz. The polarity of the activeelectrode was negative, and this polarity was maintainedthroughout the 4-week treatment period. These settingswere selected based on the results of previous stud-ies.13,19–21,23 Following treatment, the wound wasredressed in a manner consistent with the condition ofthe wound and the standard wound care protocol wedescribed earlier. All materials applied to the wounds ofthe subjects had been sterilized previously, and the activeelectrodes were discarded after each use. Universalprecautions were observed at all times, including handwashing, use of clean latex-free gloves, posttreatmentdecontamination of treatment areas and equipment,and appropriate disposal of wound care supplies.

EvaluationWound healing was assessed by a licensed physicaltherapist, nurse, or trained research assistant using pre-viously validated outcome measures36–39 during the ini-tial evaluation, following the 1- to 2-week period duringwhich subjects received only conventional wound ther-apy, after the 4-week treatment period, and at the1-month follow-up assessment. In addition, any changesin leg girth, pain, or treatment (eg, wound dressings,medications, subject adherence) during the study wererecorded. Any reports of adverse responses or of pain or

‡ Lohmann Medical, 3000 Earhart Ct, Hebron, KY 41048.

Table 2.Concurrent Wound Interventions

Subjects WhoReceived HVPCa

(n�14)

Subjects Who ReceivedSham Treatments(n�13)

Optimal wound dressing(maintains good wound moisture) 10 9

Debridement 5 4Pressure relief 3 4Compression 7 4Patient nonadherence 3 3Primary etiology not adequately

addressed 3 4

a HVPC�high-voltage pulsed current. Numbers represent the number of subjects in each group.


discomfort from subjects during the treatment sessionsalso were noted.

Outcome Measures

Wound size. The wound surface area was measured atscheduled intervals by the use of acetate tracing andsubsequent planimetric determination. This measurehas been used extensively for wounds and has estab-lished validity and reliability.36,37 Wound tracings wereaccomplished by outlining the wound circumferenceonto a transparent film (EZ Graph§) applied directlyover the wound. In order to improve the accuracy ofthese tracings, each wound was traced 3 times and thesame individual performed all wound tracings. Thisindividual had previously demonstrated on over 50wounds of mixed etiology what we consider excellentintrarater reliability with this wound measurement tech-nique (intraclass correlation coefficient �.98).40 Thewound surface area was determined from wound tracingusing a planimeter (PLANIX 7�) by a single assessor whoalso was blinded as to the identity of the subject and tothe treatment group assignment. The percentage ofdecrease in wound surface area from the wound size(%2WSA) measured during the initial evaluation wascalculated for each subject. The mean and standarderror of the mean (SEM) for the %2WSA was deter-mined for the and for the subjects who received thesham treatment. Values for %2WSA were calculated formeasurements obtained during the initial evaluation,after the 1- to 2-week period during which subjectsreceived only conventional wound therapy (prior totreatment), following the 4-week treatment period, andduring the 1-month follow-up assessment.

Wound appearance. The appearance of each woundwas assessed through direct observation of the wound atthe subjects’ bedside using the Pressure Sore Status Tool(PSST). The PSST is supposed to yield valid and reliablemeasurements that characterize changes in the appear-ance of chronic ulcers.38,39 The PSST is a pen-and-papertool with 13 domains that measure, on a scale between 1and 5, characteristics of wound size and depth, woundbed composition, wound exudate, and viability of woundedge and periulcer skin. A total PSST score between 13and 65 is derived by summing the scores given to each ofthe domains, with lower total PSST scores indicatingbetter wound appearances.

Wounds were photographed at the time of the assess-ment using a Nikon FM-2 (N-50) camera# that wasequipped to adjust automatically to variations in lighting

and with a macro lens to permit close-up images of thewound. All images included a 15.24-cm (6-in) disposableruler that had a subject identification number and datewritten on it. Care was taken to ensure that the camerawas placed perpendicular to the wound bed. The dis-tance between the camera and the wound was varied inorder to capture in the picture frame the entire wound,the ruler, and a sample of the surrounding skin (0.9–1.8 m [3–6 ft] away). These photographs were then usedto evaluate changes in wound appearance using a semi-quantitative analysis of wound appearance by the Photo-graphic Wound Assessment Tool (PWAT). The PWAT isa pen-and-paper tool consisting of 6 domains that assessthe composition of the wound bed and viability of thewound edge and periulcer skin that are capable of beingviewed using a wound photograph. Scores assigned on ascale of 0 to 4 to each of the domains of the PWAT aresummed to derive a total PWAT score between 0 and 24,with 0 representing a healed wound. The PWAT haspreviously been shown to produce reliable measure-ments of chronic leg ulcers and is responsive to changesin wound status.41

The total PSST score of wound appearance assigned byexamining the wound directly at the bedside was calcu-lated for each wound. In addition, the total PWAT scorewas determined by viewing wound photographs taken atthe same time of assessment. The mean (�SEM) of thetotal PSST scores and total PWAT scores for wounds inboth treatment groups were determined for measure-ments obtained during the initial examination, after the1- to 2-week period during which subjects received onlyconventional wound therapy, following the 4-week treat-ment period, and during the 1-month follow-upassessment.

Data Analysis

Factors affecting wound healing. The demographics ofthe subjects and coexisting medical conditions known toaffect wound healing were obtained from the subjectinterview and observation, vascular flow laboratory ses-sion, and medical chart review and are outlined in Table1. Differences in these values between treatment groupswere compared using the Student t test for parametricdata and the Mann-Whitney rank sum test for nonpara-metric data.

A secondary analysis was conducted to determine theassociation between the amount of wound healing thatoccurred during the study and subject demographics,coexisting medical conditions, and concurrent interven-tions. Pearson product moment correlation coefficientswere calculated for correlations between each of thesefactors known to affect wound healing and the amountof wound healing (%2WSA) that occurred over the

§ EZ Graph of Victoria Inc, 1606 E Brazos, Ste B, Victoria, TX 77901.� Sokkia Corp Canada, 1050 Stacey St, Mississauga, Ontario, Canada L4W 2X8.# Nikon, 1300 Walt Whitman Rd, Melvin, NY 11747-3064.


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4-week treatment period in wounds treated with eitherreal or sham HVPC.

Wound healing in combined vascular ulcers. The mean(�SEM) of the %2WSA and the total PWAT and PSSTscores representing changes in wound size and woundappearance, respectively, were calculated and comparedbetween the treatment groups. To account for the factthat multiple ulcers were treated on the same individual,a single wound was randomly selected from each subjectin both treatment groups. These values were comparedbetween the 2 groups using the Student t test. Inaddition, the change in wound size (%2WSA) andwound appearance (PWAT scores) that occurred in theHVPC- and sham-treated wounds over the time period ofthe study were analyzed statistically using a one-wayrepeated-measures analysis of variance (ANOVA). Prob-ability values less than .05 were considered statisticallysignificant.

Wound healing in bilateral venous leg ulcers. The%2WSA also was calculated for 7 subjects who hadbilateral venous leg ulcers. In these subjects, one of theulcers was randomly selected for treatment with HVPC,and the other ulcer was treated with sham HVPC.Comparison of the %2WSA between HVPC- and sham-treated wounds was done using a paired t test, and thechange in WSA that occurred over the 4 measurementperiods was analyzed statistically using a one-wayrepeated-measures ANOVA. Statistical significance wasaccepted at the 95% confidence interval.

Results

Wound Healing of Combined Vascular UlcersFollowing the 4 weeks of treatment, the %2WSA wasgreater for chronic vascular ulcers treated with HVPCthan for the sham-treated wounds (Fig. 1). There was nodifference in %2WSA between groups at the 1-monthfollow-up assessment. The %2WSA measured prior tothe start of either HVPC or sham treatments (after the 1-to 2-week period during which subjects received onlyconventional wound therapy) was minimal comparedwith %2WSA measured during the 4-week treatmentperiod and during the follow-up assessment. There wasno difference in the %2WSA that occurred over the 1-to 2-week period during which subjects received onlyconventional wound therapy between the subjectstreated with HVPC and those who received the shamtreatment, and the mean wound surface area was similarbetween groups at the time of the initial evaluation.Examination of the change in wound size that occurredover the study period revealed that there was a decreasein wound surface area over the 4-week treatment periodin the HVPC-treated wounds but not in the sham-treatedwounds.

Prior to the start of treatment, the mean PWAT scoresassigned from examining wound photographs were sim-ilar between treatment groups (Fig. 2). However, therewas a decrease in PWAT scores following the 4-weektreatment period in wounds treated with HVPC(P �.05). This improvement in wound appearance wasreflective of the loss of necrotic tissue and the relativeincrease in healthy granulation tissue present in thewound bed of HVPC-treated wounds. A similar decreasein total PWAT scores did not occur in wounds treatedwith sham HVPC. The improved wound appearanceobserved in HVPC-treated wounds was not apparent atthe 1-month follow-up assessment when the PWATscores were similar in HVPC- and sham-treated wounds.The total PSST score obtained from a bedside assess-ment of the wound produced variable results and didnot yield any detectable change in wound appearanceover time. Furthermore, total PSST scores calculated forHVPC-treated wounds (31.7�1.55) and for sham-treatedwounds (28.8�2.1) also were found to be similar for the2 treatment groups.

Wound Healing of Bilateral Venous UlcersIn the subjects who had bilateral venous leg ulcers(n�7), the ulcers that received HVPC treatment were57%�15% of original size versus 20%�18.6% for sham-treated ulcers located on the contralateral leg (P �.05,Fig. 3). The difference in the mean %2WSA after the4-week treatment period was not present at the 1-monthfollow-up assessment. There was no difference in mean

Figure 1.Mean (�SEM) of the percentage of decrease in wound surface areafrom the wound size measured during the initial evaluation calculatedfor subjects randomly selected to receive high-voltage pulsed current(HVPC) (closed bars) and subjects randomly selected to receive shamtreatment (open bars). Values were calculated from measurements takenafter the 1- to 2-week period during which subjects received onlyconventional wound therapy (pretreatment), following the 4-week treat-ment period (posttreatment), and at the 1-month follow-up assessment.Asterisk denotes statistically significant difference between treatmentgroups (P �.05, one-way analysis of variance for repeated measures).


%2WSA between the HVPC- and sham-treated woundsat the time of the initial assessment or over the 1- to2-week period during which subjects received only con-ventional wound therapy.

DiscussionThis placebo-controlled, double-blind, randomized con-trolled clinical trial demonstrated that HVPC applied tochronic leg ulcers (diabetic, arterial, or venous ulcers) 3times per week reduced the wound surface area over the4-week treatment period to approximately one half ofthe original size. This rate of wound closure was appro-priately twice that observed in wounds treated identicallywith sham HVPC. The ability of HVPC to stimulatewound healing of chronic leg ulcers was particularlyevident in 7 subjects with bilateral venous ulcers wherethe HVPC-treated wounds had consistently faster woundclosure rates than did sham-treated wounds located onthe contralateral limbs of the same individuals. Wereviewed notes taken after each treatment session andfound that no adverse reactions occurred during thecourse of any of the treatments. Therefore, we believethat therapy involving the use of electrical current canbe applied in comfortable manner that is relativelypainless to the patient with minimal safety concerns.

Our study was performed within a single research centerthat involved a relatively small sample size (27 subjects

with 42 ulcers). However, our sample size was sufficientto detect differences that we believe are clinically mean-ingful. Prior to the study, we determined that a samplesize of 12 subjects per group would be required to detectdifferences between treatment groups with a statisticalpower of 80%. Additionally, based on calculations ofeffect size using data collected from the 27 subjectsenrolled in this study, we determined that we had 80%power to detect at least a 10% difference in %2WSAbetween treatment groups. That is, differences of lessthan 10% between treatment groups would not bedetected in this study (Type II statistical error), which isreasonable because we would not consider differencesless than this to be clinically meaningful.

In this study, we monitored and recorded all factors webelieved could affect wound healing such as subjectdemographics, coexisting medical conditions, and con-current standard wound care interventions. No differ-ence in these factors was detected between the subjectswho received HVPC and the subjects who received thesham treatment. We believe, therefore, it is likely thatthe observed acceleration in healing was attributable tothe exogenous application of electrical current to thewound bed rather than being due to other factors.

The beneficial effects of HVPC that we observed were ina sample who were, on average, over the age of 60 yearsand had an average wound history of 3 to 5 years withseveral coexisting medical conditions known to interfere

Figure 2.Mean (�SEM) of the total Photographic Wound Assessment Tool(PWAT) score assigned by a single observer from an assessment ofwound appearance using a wound photograph. Total scores werecalculated for subjects randomly selected to receive high-voltage pulsedcurrent (HVPC) (square symbols) and subjects randomly selected toreceive sham treatment (diamond-shaped symbols). Values were calcu-lated from measurements obtained from photographs taken after the 1-to 2-week period during which subjects received only conventionalwound therapy (pretreatment), following the 4-week treatment period(posttreatment), and at the 1-month follow-up assessment. Asteriskdenotes statistically significant difference between treatment groups(P �.05, Mann-Whitney rank sum test).

Figure 3.Mean (�SEM) of the percentage of decrease in wound surface areafrom the wound size measured during the initial evaluation calculatedfor 7 subjects who had bilateral venous leg ulcers. In these subjects, oneof the ulcers was randomly selected to be treated with high-voltagepulsed current (HVPC) (closed bars) and the other ulcer was treated withsham HVPC (open bars). Values were calculated from measurementstaken after the 1- to 2-week period during which subjects received onlyconventional wound therapy (pretreatment), following the 4-week treat-ment period (posttreatment), and at the 1-month follow-up assessment.Asterisk denotes statistically significant difference between treatmentgroups (P �.05, one-way analysis of variance for repeated measures).


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with their ability to heal. Healing rates in both HVPC-and sham-treated wounds were inversely related to thenumber of factors affecting wound healing and to theinability to manage the primary wound etiology such aspoorly controlled blood glucose concentrations. There-fore, we believe the benefits of this therapeutic approachare best obtained in conjunction with an optimal woundmanagement program that addresses the underlyingcause of the wound and reduces the factors workingagainst wound healing.

The changes in wound healing that occurred over thestudy period were evaluated using measurements ofwound size and wound appearance. These measure-ments were taken by a single observer who was blindedto the treatment groups, thus, we contend, reducingrater bias. Measurements of wound surface area usingacetate tracings with subsequent planimetry have beenshown to be sensitive to change over time.36,37 Thistechnique of determining wound size has been recom-mended by researchers42 who have systematically com-pared numerous wound measurement tools that arecurrently available. Although a more accurate descrip-tion of wound extent should include measurements ofwound depth or volume, we did not measure thesevariables in our study because measurement tools thatproduce reproducible and accurate measurements ofwound depth or volume are not readily available.

We expressed wound healing as a percentage of changein order to normalize large variations in initial woundsize that existed in each treatment group. The use ofpercentage of decrease in wound size as an index of rateof healing has been used in previous reports.13,18 We alsodetermined the change in surface area from the initialevaluation and the percentage of initial wound size andfound that regardless of how wound healing wasexpressed, HVPC treatment consistently produced bet-ter outcomes than the sham treatment.

Wound appearance was assessed using the well-established PSST38,39 and by using a recently developedtool that has been modified for use on wound photo-graphs (PWAT).41 Changes in wound appearance overthe 4-week treatment period occurring in woundstreated with HVPC were detected when the change intotal PWAT scores was examined. Examination of thechange in total PSST scores did not show a differenceover time in either treatment group, nor was a differencedetected in PSST scores between the subjects whoreceived HVPC and the subjects who received the shamtreatment. These findings were not surprising becausealthough the PSST has been validated and used exten-sively to assess the appearance of chronic pressureulcers,38,39 no published reports exist to demonstrate thevalidity and reliability of PSST measurements for assess-

ing leg ulcers due to vascular insufficiency. Recently, thevalidity and reliability of PWAT scores were tested instudy in which 56 pressure ulcers and 81 chronic legulcers were rated by 5 independent observers, and thePWAT was found to have excellent reliability, concur-rent validity, and sensitivity to change.41

These measurements of wound size and appearancewere taken after 4 weeks of treatment. This duration oftreatment is consistent with that used in other clinicaltrials of other wound care treatments. Previous stud-ies8,13,28,43 have demonstrated that 4 weeks of treatmentis sufficient to evaluate the efficacy of wound treatment.Although 4 weeks of treatment was sufficient to assessthe effectiveness of the HVPC treatment, it was not longenough to produce complete wound closure. Initialimprovements in wound closure rate were no longerobvious 1 month following completion of the 4-weektreatment program. Therefore, continued HVPC treat-ments of greater than 4 weeks or until wound closureneed to be studied to determine whether improvementsin the healing of these chronic leg ulcers would occur.

A standardized wound care program was provided in ourstudy to both subjects who received HVPC and subjectswho received the sham treatment. A variety of dressingmaterials were used in an effort to promote moistinteractive healing and to optimize the wound environ-ment. This approach to dressing selection is consistentwith most published recommendations that the “bestdressing” is one that meets the functions and character-istics of the wound and considers the needs of thepatient.44,45 Research examining the influence of variousdressing types on the rate of wound closure has yieldedinconclusive results and has not identified any particularsuperior dressing.23 Therefore, it is unlikely that differ-ent dressings utilized by subjects enrolled in the studycontributed to accelerated wound closure rates observedfollowing HVPC treatments. There is research evidenceto suggest that appropriate and timely debridementprocedures can accelerate wound closure46; however, anequal number of subjects in each treatment group in ourstudy received relatively minor wound debridementprocedures.

Electrically induced acceleration of wound closure insubjects with leg ulcers due vascular compromise causedby diabetes mellitus has been demonstrated in 4 studies,including 2 randomized controlled clinical trials.24–27

Thurman and Christian24 reported on a subject withjuvenile diabetes who had a nonhealing ulcer located onthe toes. In this case, HVPC was used to heal the woundand as a result avoided a previously scheduled footamputation. Lundeberg et al,26 in a well-controlledclinical trial, found differences in the percentage ofhealed ulcer area and the number of healed ulcers


treated with electrotherapy compared with those receiv-ing sham treatment.

Baker et al27 conducted a prospective randomized clin-ical trial involving 80 subjects with diabetes and 114open wounds. They demonstrated that the applicationof electrical stimulation using an asymmetrical biphasicwaveform accelerated the healing of wounds in peoplewith diabetes. The healing rates they observed, however,in patients with diabetes were lower than those found forpressure ulcers by the same investigators in a differentstudy.9 Slower healing rates induced by electrical stimu-lation observed in people with diabetic ulcers versuspressure ulcers are presumably due to the numerousnegative effects that diabetes has on wound healing.47

Therefore, although electrical stimulation is effective inaccelerating wound closure of diabetic ulcers, we expectthe expected rate of healing to be lower than for othertypes of ulcers.

There is little research that has examined the effect ofelectrical stimulation on chronic venous ulcers. In 1968,Assimacopoulos28 presented 3 case reports describingthe use of low-intensity direct current to stimulatewound closure in subjects with chronic venous insuffi-ciency. The wounds had not responded to previoustreatments. Although the case reports suggest that elec-trotherapy may be beneficial in managing chronicvenous ulcers, no subsequent controlled clinical trial hasconfirmed these findings. In 1987, Katelaris et al29

reported on the effects of electrical stimulation onchronic venous ulcers. The electrical current, however,was administered in combination with povidone-iodinesolution. This negative result is not surprising given whatis now known about the cytotoxic effects of povidone-iodine solution.48 Therefore, we believe that our studyrepresents the first properly designed clinical trial todemonstrate that direct application of HVPC to thewound bed produces faster closure of chronic venousulcers compared with sham-treated wounds.

The electrical stimulus settings used in our study wereselected based on results of previous studies.13,19–21,25

Electrical stimulation in our study was delivered using amonopolar setup with the active electrode placeddirectly in to the wound bed using specialized electrodescomposed of sterile conductive material and a largerdispersive electrode placed on intact skin close to thewound. Placement of the active electrode directly in thewound bed is the electrode placement used most oftenwhen administering HVPC waveforms.13,19–21,25 How-ever, successful outcomes also have been reported whenusing other waveforms of electrical current such asasymmetrical biphasic pulsed current delivered throughelectrodes placed on periulcer skin.27

The frequency and duration of treatments reported inthe literature vary greatly. Most authors suggest that theoptimal treatment schedule necessary to produce maxi-mal tissue healing response is not known, but, in gen-eral, it is recommended that treatments should be givenfor 1 hour a day, 5 times a week, in order to stimulatewound closure.49,50 We found that electrical currentdelivered for only 45 minutes 3 times a week wasbeneficial. Although it is probable that more frequenttreatments would optimize wound healing, this is notalways feasible for people living in the community. Ourtreatment protocol was selected to accommodate indi-viduals being treated in an outpatient setting.

ConclusionOur results demonstrated that HVPC administered 3times per week for 4 weeks to chronic vascular leg ulcersproduced a reduction in wound size and an improve-ment in wound appearance as compared with sham-treated wounds. Therefore, it appears that electrother-apy treatments of the type we used are not only effectivein managing chronic pressure ulcers but also should beused to accelerate wound healing of chronic vascular legulcers. Further work is needed to determine the exactmechanism(s) underlying the electrically inducedwound repair and to elucidate electrical stimulationsettings, electrode setups, and treatment schedules. Mostimportantly, future research is needed to determinewhether the type of electrical stimulation we used can beconducted in a manner that not only decreases woundsize but also leads to wound closure.

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