Effectiveness of Wound Care Products in the Transmission of Acoustic Energy.

Ultrasound continues to be used by physical therapists to stimulate wound healing.[1] In our opinion, however, data on appropriate techniques and dosage[3] for delivering acoustic energy to wounds are limited. Wound care with ultrasound has been performed in the following ways: directly around the wound,[1,3-9] in a water bath[1,9-11] using a condom method,[12] directly over the wound with an ultrasound gel medium,[13-16] using saline within the wound cavity,[11] or over various hydrogels[8,9,12,17-21] and semipermeable film dressings.[8,21-23] Because some authors have recommended treating broken skin only through a sterile and inert coupling medium[1,24] and because some techniques such as sonation around the wound appear to make it "impossible to keep the ulcers sterile,"[3(p233)] the use of wound care products as barriers between the wound and the ultrasound equipment has become popular.

Although the effects of various wound care dressings on diagnostic ultrasound imaging have been examined,[25,26] there is a paucity of evidence regarding the transmissivity of these materials for therapeutic ultrasound. Therefore, the purpose of this in vitro study was to examine the ultrasound transmissivity of 4 hydrogel sheets and 4 film dressings used for wound care.

Method

Instrumentation

An Intelect Legend ultrasound unit,(*) which the manufacturer states has a 5.0-[cm.sup.2] sound head(*) and an effective radiating area of 4.0 [+ or -] 1.0 [cm.sup.2] ([bar]X [+ or -] SD), was used to deliver acoustic energy. The receiving transducer(*) was the same model as the delivering transducer. The receiving transducer was modified([dagger]) so a bus net connector could be attached. With the bus net connector, the receiving sound head could be connected to an oscilloscope. The amount of sound energy received was read as peak-to-peak (peak-peak) voltage from a Gould digital storage oscilloscope([double dagger]) (Fig. 1). The beam nonuniformity ratio of each ultrasound applicator was specified by the manufacturer as 6:1. The ultrasound equipment was calibrated([dagger]) prior to the taking of any measurements. All experiments were conducted with continuous wave ultrasound at a frequency of 3.3 MHz, which has become popular for superficial wounds[12,20] and deep wounds.[12]

[Figure 1 ILLUSTRATION OMITTED]

A platform apparatus (Fig. 2) was used to carry out the pilot trials and the experiment. The apparatus was mounted on a 22.5-kg (50-lb) aluminum plate. Four aluminum rods, which were 0.635 cm (1/4 in) in diameter, were fixed in the plate 17.8 cm (7 in) apart. A Plexiglas([sections]) platform was fitted to slide up and down on the rods. The bottom platform had a hole drilled in the center with the exact dimensions of the receiving sound head. The sound head was placed underneath the platform flush with the Plexiglas. The transducer was secured in foam to protect the crystal, held in place with a vise, and made level with the bottom platform. The transmitting transducer was housed in another piece of Plexiglas with the same dimensions as the bottom platform. This top piece of Plexiglas was aligned directly above the bottom platform and receiving sound head. The transmitting sound head was secured to the top plate using a Plexiglas collar, which was allowed to slide horizontally, to tighten around the sound head. This apparatus allowed for one movable piece during data collection. The top piece of Plexiglas, with the transmitting sound head attached to it, was only permitted to move vertically along the 4 aluminum rods. Between setups, the top plate was raised to remove one wound care product interface and add another. A 3-dimensional level was used to keep the Plexiglas plates and transducers parallel with each other.

[Figure 2 ILLUSTRATION OMITTED]

Materials

In this study, we examined the transmissivity of ultrasound through 4 film dressings and 4 hydrogel sheets, with pig tissue as a constant interface. The 4 film dressings examined were CarraSmart Film,([parallel]) Tegaderm,(#) J&J Bioclusive,(**) and Opsite Flexigrid.([dagger])([dagger]) The hydrogels examined were CarraDres,([parallel]) Aquasorb Border,([double dagger])([double dagger]) Nu-Gel,(**) and ClearSite.([subsections])

We used pig tissue in this study due to its physiologic similarity to human tissue.[27] The tissue was cut fresh, frozen, then thawed prior to use. It was shaved to decrease attenuation of acoustic/ultrasound energy and to avoid air bubbles becoming trapped in the hair. The tissue dimensions were 11.5 x 8.2 cm, with 0.5 cm of subcutaneous fat. The same piece of tissue was used throughout this experiment. The experiment was conducted in a ventilated room at a temperature of 22 [degrees] C.

Pilot Studies

A pilot study was conducted to test the intertrial reliability of obtained measurements. Five setups with 3 trials per setup were performed. A 5-minute rest interval was allotted between trials, and at least 5 minutes elapsed between setups. Each setup included elevating the top plate with the secured transmitting sound head, replacing it on the interposed tissue, and leveling it out. Voltage output readings from the first setup were lower compared with voltage output readings taken from setups 2 through 5. The readings from the first apparatus setup were consequently discarded. The mean ([+ or -] SD) of the 12 acceptable trials between the 4 setups was 1.70 [+ or -] 0.04 V. This measurement yielded a coefficient of variation of 2.15%, which we considered sufficient to proceed with the experiment.

A second pilot study was conducted to determine whether the order of presentation of the sound wave intensities caused sequence effects that would affect subsequent sound wave transmission. Three trials were conducted, with a 5-minute rest interval between trials. The interposed materials consisted of pig tissue between 2 gel pads. Similar peak-peak voltage output was found for each trial at each intensity, regardless whether the order of intensities was conducted from lowest to highest intensity (0.2-2.0 W/[cm.sup.2]), from highest to lowest intensity, or randomized. We concluded that any short-term transmissivity changes in the tissue in response to sonation were dissipated during the 5-minute rest interval. This pilot work supported our decision to use a single piece of pig tissue as a constant throughout the experiment.

Procedure

Three trials were performed at each of 5 intensities for baseline data collection and for each wound care product interface. The intensities were 0.2, 0.5, 1.0, 1.5, and 2.0 W/[cm.sup.2]. The baseline setup included a piece of pig tissue placed between the sound heads. Ultrasound gel was placed at each interface. Any large air bubbles in the gel at the receiving sound head interface were removed by a syringe. Following the collection of the baseline data, each of the 4 hydrogel dressings and the 4 film dressings were tested in randomized order. A thin layer of ultrasound gel was placed on the pig tissue before the film dressing or hydrogel was applied in order to prevent reflection of the acoustic energy. Air that became entrapped as the dressing was applied was removed by applying light pressure across the dressing with a sterile tongue depressor. A thin layer of gel was placed on the outer surface of the dressing to decrease sound energy impedance as a result of air.[1,8,12,18,19,23,28] The wound dressings were handled only by the edges to avoid the accumulation of any body oils that could have interfered with the testing. Before applying the hydrogel dressing, the bottom plastic film was first removed. In cases where the hydrogel dressing was protected with a removable plastic film on both sides, the top film was also removed. Once the bottom plate and receiving sound head were level and the tissue sample with the wound dressing was in place, the top plate was lowered until the transmitting transducer contacted the material. The top plate was then made parallel with the bottom plate using a 3-dimensional level.

Three trials were done at each intensity for each interposed material. The interface was not touched until 3 trials at each intensity were recorded. The ultrasound unit was turned on and ramped to the desired intensity. Once the sine wave became stable (approximately 2 seconds after reaching the desired intensity), the peak-peak voltage output was recorded from the oscilloscope. The ultrasound unit was then shut off and a 5-minute cooling-off period followed. After data collection, the top plate was raised, and the interposed material was removed. The process was then repeated. Between setups, the apparatus and interface were examined for ally debris that might interfere with the trials. After new ultrasound gel was placed at each interface and another dressing was applied to the pig tissue, the process was repeated. The same tester performed each setup. Another tester was responsible for ramping the ultrasound to the desired intensity.

Data Reduction and Analysis

We normalized our voltage data with the different wound product interfaces by using the voltages obtained at baseline. To normalize the voltage data, we first calculated the average baseline voltage at each intensity. Then, we converted each raw voltage value into a percentage of voltage by dividing by the mean baseline voltage for the corresponding intensity. The converted percentage of voltage data were then used in our statistical analyses.

We used a one-way analysis of variance (ANOVA) to compare transmissivity (expressed as percentage of baseline voltage) of the 9 interfaces, including 8 experimental conditions and the baseline of only gel and pig tissue. Post hoc comparisons were done with the Scheffe test. The alpha level was set at .05 for all analyses.

Results

The mean voltages for each film dressing and hydrogel at each intensity are shown in Table 1 and are illustrated in Figures 3 and 4, respectively. The ANOVA identified differences in percentage of voltage across materials (F=526.48, P [is less than] .01). Table 2 and Figure 5 show the post hoc results. The 6 different subsets, in decreasing order of transmissivity, were as follows: (1) gel baseline (100%), (2) Nu-Gel (77.2% [+ or -] 4.6%) and ClearSite (72.0% [+ or -] 2.2%), (3) CarraSmart Film (60.5% [+ or -] 4.4%), (4) J&J Bioclusive (53.2% [+ or -] 2.4%), (5) Tegaderm (47.1% [+ or -] 2.3%), Aquasorb Border (45.3% [+ or -] 2.1%), and CarraDres (42.8% [+ or -] 5.9%), and (6) Opsite Flexigrid (31.5% [+ or -] 4.0%).

[Figures 3-5 ILLUSTRATION OMITTED]

Table 1. Average ([+ or -] SD) of Three Trials in Peak-Peak Voltage Output for Hydrogels and Film Dressings at the Specified Intensities

                              Intensity (W/[cm.sup.2])

Interface                     0.2                  0.5

Baseline
  Pig tissue + gel     2.40 [+ or -] 0.10   3.68 [+ or -] 0.04

Hydrogel
  CarraDres            1.24 [+ or -] 0.08   1.66 [+ or -] 0.05
  Aquasorb Border      1.10 [+ or -] 0.00   1.72 [+ or -] 0.05
  Nu-Gel               1.86 [+ or -] 0.05   2.99 [+ or -] 0.09
  ClearSite            1.72 [+ or -] 0.08   2.73 [+ or -] 0.09

Film dressing
  CarraSmart Film      1.60 [+ or -] 0.03   2.17 [+ or -] 0.20
  Tegaderm             1.18 [+ or -] 0.02   1.78 [+ or -] 0.04
  J&J Bioclusive       1.30 [+ or -] 0.03   2.07 [+ or -] 0.06
  Opsite Flexigrid     0.91 [+ or -] 0.02   1.19 [+ or -] 0.07

                              Intensity (W/[cm.sup.2])

Interface                     1.0                  1.5

Baseline
  Pig tissue + gel     5.16 [+ or -] 0.10   6.80 [+ or -] 0.03

Hydrogel
  CarraDres            2.14 [+ or -] 0.05   2.59 [+ or -] 0.09
  Aquasorb Border      2.45 [+ or -] 0.07   2.86 [+ or -] 0.06
  Nu-Gel               4.22 [+ or -] 0.10   5.06 [+ or -] 0.13
  ClearSite            3.82 [+ or -] 0.09   4.70 [+ or -] 0.06

Film dressing
  CarraSmart Film      2.92 [+ or -] 0.07   3.86 [+ or -] 0.13
  Tegaderm             2.52 [+ or -] 0.02   3.01 [+ or -] 0.02
  J&J Bioclusive       2.78 [+ or -] 0.02   3.41 [+ or -] 0.09
  Opsite Flexigrid     1.58 [+ or -] 0.04   1.90 [+ or -] 0.06

                       Intensity (W/[cm.sup.2])

Interface                        2.0

Baseline
  Pig tissue + gel        7.76 [+ or -] 0.05

Hydrogel
  CarraDres               2.90 [+ or -] 0.03
  Aquasorb Border         3.46 [+ or -] 0.10
  Nu-Gel                  5.50 [+ or -] 0.07
  ClearSite               5.48 [+ or -] 0.07

Film dressing
  CarraSmart Film         4.93 [+ or -] 0.15
  Tegaderm                3.49 [+ or -] 0.03
  J&J Bioclusive          4.00 [+ or -] 0.19
  Opsite Flexigrid        2.22 [+ or -] 0.07

Table 2. Homogeneous Subsets Identified by Scheffe Test(a)

                                     Homogeneous Subset

Material                             1               2

Baseline                           100.0%
Nu-Gel hydrogel                             77.2% [+ or -] 4.6%
ClearSite hydrogel                          72.0% [+ or -] 2.2%
CarraSmart Film film dressing
J&J Bioclusive film dressing
Tegaderm film dressing
Aquasorb Border hydrogel
CarraDres hydrogel
Opsite Flexigrid film dressing

                                   Homogeneous Subset

Material                                    3

Baseline
Nu-Gel hydrogel
ClearSite hydrogel
CarraSmart Film film dressing      60.5% [+ or -] 4.4%
J&J Bioclusive film dressing
Tegaderm film dressing
Aquasorb Border hydrogel
CarraDres hydrogel
Opsite Flexigrid film dressing

                                   Homogeneous Subset

Material                                    4

Baseline
Nu-Gel hydrogel
ClearSite hydrogel
CarraSmart Film film dressing
J&J Bioclusive film dressing       53.2% [+ or -] 2.4%
Tegaderm film dressing
Aquasorb Border hydrogel
CarraDres hydrogel
Opsite Flexigrid film dressing

                                   Homogeneous Subset

Material                                    5

Baseline
Nu-Gel hydrogel
ClearSite hydrogel
CarraSmart Film film dressing
J&J Bioclusive film dressing
Tegaderm film dressing             47.1% [+ or -] 2.3%
Aquasorb Border hydrogel           45.3% [+ or -] 2.1%
CarraDres hydrogel                 42.8% [+ or -] 5.9%
Opsite Flexigrid film dressing

                                   Homogeneous Subset

Material                                    6

Baseline
Nu-Gel hydrogel
ClearSite hydrogel
CarraSmart Film film dressing
J&J Bioclusive film dressing
Tegaderm film dressing
Aquasorb Border hydrogel
CarraDres hydrogel
Opsite Flexigrid film dressing     31.5% [+ or -] 4.0%

(a) Means ([+ or -] SD) are given for the percentage of voltage transmitted compared with the baseline voltage.

Discussion

The results indicate a wide variation across the 8 wound care product interfaces. The overall transmissivity range was from the 70% range (Nu-Gel at 77.2% and ClearSite at 72.0%) to the 30% range (Opsite Flexigrid at 31.5%). There were wide variations within each product type as well. For instance, the transmissivity range for hydrogels was from 70% (Nu-Gel and ClearSite) to 40% (Aquasorb at 45.3% and CarraDres at 42.8%); the range for film dressings was from 60.5% (CarraSmart Film) to 31.5% (Opsite Flexigrid).

Various wound characteristics, conditions, and wound care treatment goals may influence which dressing type would be most appropriate for a particular wound.[8,24,28-30] For instance, hydrogel dressings absorb fluids and are used to manage moderate amounts of drainage.[8,24,28-30] Film dressings, in contrast, do not have absorption capabilities and can handle only minimal amounts of drainage.[8,24,28-30] In addition, hydrogel dressings may offer cushioning and a cooling sensation to the wound.[24,28,30] Generally speaking, minimal, if any, irritation to the intact periwound tissue is expected on removal of a hydrogel, whereas the removal of a film dressing is thought to require greater care in those instances where the surrounding skin is fragile.[28,29]

Film dressings do not require a secondary dressing.[24,28-30] However, because exudate may pass through hydrogel dressings, using a secondary dressing is advised.[24,28-30] In contrast to hydrogel dressings, which are thought to be "unable alone to keep out bacteria,"[29(p166)] film dressings are thought to protect a wound from microbes and bacteria.[24,28-30] Some authors contend that film dressings may remain in place for up to 1 week, whereas hydrogels generally need to be changed every 3 to 4 days.[28] Clinicians, we believe, should make clinical decisions on the type of wound care dressing used for ultrasound treatment based on attributes of the dressing, including the transmissivity of the dressing.

Our results have varied levels of agreement with the few results presented in the literature. We recorded that 47% of ultrasound energy was transmitted through Tegaderm compared with the baseline recording. This percentage is similar to the finding of 40% of Byl and colleagues.[23] In contrast, Nussbaum[21] reported that only 10% of "ultrasound power" was transmitted through an Opsite Flexigrid film dressing; we found that 31% transmitted through Opsite Flexigrid.

The only study of hydrogel transmissivity we found was of Geliperm([parallel])([parallel]) by Brueton and Campbell[17] in 1987. The Geliperm was kept under water during the experiment[17] and was attached directly to the face of the sound head.[21] This procedure, which did not mimic clinical conditions, resulted in 95% transmission of the sound energy through the Geliperm. We were unable to obtain Geliperm for our study as it is currently available in Europe but not in the United States.[8]

Although we attempted to carefully control the experimental setup, we did not measure and control for pressure variations of the sound head. Pressure variation has been found to influence acoustic energy transmission.[31] This potential for variation may have affected our results.

Our in vitro study did not mimic the varying wound conditions seen clinically in terms of wound depth, drainage amount and composition, whether a full-thickness wound should be filled with sterile normal saline solution[1,19-21] or a sterile gel,[12,20] and so on. We were aware of these limitations but chose to control the experimental variables as much as was possible in order to focus on the transmission capabilities of the wound care products. The percentage of ultrasound transmission through a film dressing or hydrogel is not the only factor relevant to wound healing. However, clinicians can use our findings as a part of the clinical reasoning process that they use to select an optimal wound dressing.

There are other factors to consider in deciding which product or product type to use in the treatment of wounds with ultrasound, including cost, whether a sterile or clean technique is warranted, and the potential for cross-contamination. As we noted, one disadvantage of a hydrogel is its inability to keep bacteria out of the wound without the aid of a secondary dressing.[29]

An additional consideration with some of the hydrogels is that the clinician needs to decide whether to remove the outer polyethylene film during sonation, as we did during our study. This has been suggested for those occasions when clinicians want to increase the vapor transmission rate of the wound[24,29] or when electrical stimulation with a reusable electrode is going to be conducted.[12] If the outer film is removed during sonation, replacing the film on the dressing after treatment or covering the wound with another appropriate film to prevent dehydration of the dressing can be done. If a sterile technique is desired or there is the concern with cross-contamination, it may be appropriate to replace the sonated hydrogel dressing with a new dressing following treatment.

We recommend that future research should address the optimum amount of acoustic energy that is needed to be received in order to best assist aid the wound healing process and outcome. In addition, we suggest that further research is needed on the acoustic energy transmission of hydrogels with and without the polyethylene film in place.

Summary

The transmissivity range for hydrogels was from more than 70% (77.2% for Nu-Gel and 72.0% for ClearSite) to approximately 40% (42.8% for CarraDres). The transmissivity range for the film dressings was from approximately 60% (60.5% for CarraSmart Film) to approximately 30% (31.5% for Opsite Flexigrid).

(*) Chattanooga Group Inc, 4717 Adams Rd, Hixson, TN 37343.

([dagger]) Methodist Hospital of Indiana Inc, Biomedical Engineering Department, 1701 N Senate Blvd, Indianapolis, IN 46202.

([double dagger]) Gould Instrument Systems, Roebuck Rd, Hainault, Ilford, Essex, IG6 3UE England.

([sections]) Rohm & Haas Co, Independence Mall W, Philadelphia, PA 19105.

([parallel]) Carrington Laboratories Inc, 2001 Walnut Hill Ln, Irving, TX 75038.

(#) 3M, Medical-Surgical Division, Bldg 275-4E-01, St Paul, MN 55144-1000.

(**) Johnson & Johnson Medical Inc, 2500 Arbrook Blvd, PO Box 90130, Arlington, TX 76004.

([dagger])([dagger]) Smith & Nephew, Wound Management Division, 11775 Starkey Rd, Largo, FL 33773.

([double dagger])([double dagger]) DeRoyal Industries Inc, 200 DeBusk Ln, Powell, TN 37849.

([subsections]) CONMED Carp, 310 Broad St, Utica, NY 13501.

([parallel])([parallel]) Geistlich Sons Ltd, Long Lane, Chester, CH2 2PF England.

References

[1] Dyson M. Role of ultrasound in wound healing. In: McCulloch JM, Kloth LC, Feedar JA, eds. Wound Healing: Alternatives in Management. 2nd ed. Philadelphia, Pa: FA Davis Co; 1995:319-345.

[2] Reid DC, Cummings GE. Factors in selecting the dosage of ultrasound: with particular reference to the use of various coupling agents. Physiotherapy Canada. 1973;25:5-9.

[3] Dyson M, Franks C, Suckling J. Stimulation of healing of varicose ulcers by ultrasound. Ultrasonics. 1976;14:232-236.

[4] Dyson M, Suckling J. Stimulation of tissue repair by ultrasound: a survey of the mechanisms involved. Physiotherapy. 1978;64:105-108.

[5] Callam MJ, Harper DR, Dale JJ, et al. A controlled trial of weekly ultrasound therapy in chronic leg ulceration. Lancet. 1987;2(8552): 204-206.

[6] Roch C, West J. A controlled trial investigating the effect of ultrasound on venous ulcer referred from general practitioners. Physiotherapy. 1984;70:475-477.

[7] Nussbaum EL, Biemann I, Mustard B. Comparison of ultrasound/ ultraviolet-C and laser for treatment of pressure ulcers in patients with spinal cord injury. Phys Ther. 1994;74:812-823.

[8] Sussman C, Dyson M. Therapeutic and diagnostic ultrasound. In: Sussman C, Bates-Jensen BM, eds. Wound Care: A Collaborative Practice Manual for Physical Therapists and Nurses. Gaithersburg, Md: Aspen Publishers Inc; 1998:427-445.

[9] McDiarmid T, Ziskin MC, Michlovitz SL. Therapeutic ultrasound. In: Michlovitz SL, ed. Thermal Agents in Rehabilitation. 3rd ed. Philadelphia, Pa: FA Davis Co; 1996:192-200.

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[11] McCulloch J. Physical modalities in wound management: ultrasound, vasopneumatic devices and hydrotherapy. Ostomy Wound Manage. 1995;41(5):30-32, 34, 36-37.

[12] Phillips J. Ultrasound in wound healing. In: Merkel MJ, Phillips J, eds. Solving the Problems of Slow Healing Wounds. Indianapolis, Ind: Accelerated Wound Healing Seminars; 1997:35-38.

[13] Shamberger RC, Talbot TL, Tipton HW, et al. The effect of ultrasonics and thermal treatment on wounds. Plast Reconstr Surg. 1981;68:860-870.

[14] Eriksson SV, Lundeberg T, Malm M. A placebo controlled trial of ultrasound therapy in chronic leg ulceration. Scand J Rehabil Med. 1991;23:211-213.

[15] Creates V. A study of ultrasound treatment to the painful perineum after childbirth. Physiotherapy. 1987;73:162-165.

[16] ter Riet G, Kessels AGH, Knipschild P. A randomized clinical trial of ultrasound in the treatment of pressure ulcers. Phys Ther. 1996;76: 1301-1311.

[17] Brueton RN, Campbell B. The use of Geliperm as a sterile coupling agent for therapeutic ultrasound. Physiotherapy. 1987;73:653-654.

[18] Young SR, Dyson M. The effect of therapeutic ultrasound on angiogenesis. Ultrasound Med Biol. 1990; 16:261-269.

[19] Young SR, Dyson M. Effect of therapeutic ultrasound on the healing of full-thickness excised skin lesions. Ultrasonics. 1990;28:175-180.

[20] Feedar JA. Physical therapy modalities to augment wound healing. Topics in Geriatric Rehabilitation. 1994(a);9(4):43-57.

[21] Nussbaum EL. Therapeutic ultrasound. In: Behrens BJ, Michlovitz SL, eds. Physical Agents: Theory and Practice for the Physical Therapist Assistant. Philadelphia, Pa: FA Davis Co; 1996:81-117.

[22] Byl NN, McKenzie AL, West JM, et al. Low-dose ultrasound effects on wound healing: a controlled study with Yucatan pigs. Arch Phys Med Rehabil. 1992;73:656-664.

[23] Byl NN, McKenzie A, Wong T, et al. Incisional wound healing: a controlled study of low and high dose ultrasound. J Orthop Sports Phys Ther. 1993;18:619-628.

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[25] Whiteley MS, Magee TR, Harris R, Horrocks M. Colour Duplex imaging through wound dressings. Eur J Vasc Surg. 1993;7:713-716.

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[27] Lehmann JF, McMillan JA, Brunner GD, Blumberg JB. Comparative study of efficiency of short wave, microwave, and ultrasonic diathermy in heating hip joint. Arch Phys Med Rehabil. 1959;40:510-512.

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B Klucinec, PT, MS, ATC, is Physical Therapist, Joyner Sportsmedicine Institute Inc, 2525 9th Ave, Suite IA, Altoona, PA 16602 (USA). Address all correspondence to Mr Klucinec.

M Scheidler, PT, MS, is Physical Therapist, Hancock Memorial Hospital and Health Services, Greenfield, Ind.

C Denegar, PT, PhD, ATC, is Associate Professor, Department of Orthopedics and Rehabilitation, and Associate Professor in Kinesiology, Pennsylvania State University, University Park, Pa.

E Domholdt, PT, EdD, is Professor and Dean, Krannert School of Physical Therapy, University of Indianapolis, Indianapolis, Ind.

S Burgess, PT, MS, Assistant Professor of Physical Education, Ball State University, Muncie, Ind.

Mr Klucinec, Mr Scheidler, Mr Denegar, and Dr Domholdt provided concept/idea/research design. Mr Klucinec, Mr Scheidler, Dr Domholdt, and Ms Burgess provided writing. Data collection was provided by Mr Klucinec, Mr Scheidler, and Ms Burgess, and data analysis was provided by Mr Scheidler, Mr Denegar, and Dr Domholdt. Project management was provided by Mr Klucinec and Mr Scheidler; institutional liaisons, by Mr Klucinec; and facilities/equipment, by Dr Domholdt. Mr Denegar and Ms Burgess provided consultation (including review of manuscript before submission). The Physical Therapy Department of Slippery Rock University provided the oscilloscope used in this study; Bert Goebel (Kees Goebel Medical) and Chattanooga Group provided the ultrasound equipment; Steve Wood, James Phillips, and Johnson &Johnson provided wound care supplies; and the Biomedical Engineering Department at Methodist Hospital of Indiana Inc provided modification and calibration of equipment.

Funding for this project was provided by the University of Indianapolis.

This article was submitted February 22, 1999, and was accepted January 13, 2000.