A Randomized, Controlled Study to Compare the Effectiveness of Two Foam Dressings in the Management of Lower Leg Ulcers

   Polyurethane foam dressings are commonly used in the treatment of chronic wounds, including leg,1,2 decubitus,1 and diabetic foot ulcers.3 They absorb exudate, prevent maceration and leakage, and control odor.1,2 Their exudate handling properties also may have a positive impact on the treatment cost of exuding ulcers.4

   The purpose of this prospective, randomized, controlled clinical study was to compare a new, nonadhesive polyurethane foam dressing to a hydrocellular dressing in the management of moderately to heavily exuding venous ulcers. The effect of both dressings on healing and periulcer skin condition and their ability to manage exudate were assessed.

Methods

   Patients and study design. One hundred and eighteen consecutive patients in four European sites were recruited to participate in this study. All patients were treated in outpatient clinics of University Hospitals in the Netherlands or Denmark. Patients presenting with moderately to highly exuding leg ulcers of at least 3 weeks' duration were eligible to participate if the primary etiology of each ulcer was venous insufficiency and the wound was not larger than 9 cm x 9 cm. Patients younger than 18 years of age, pregnant women, people with an ankle/brachial index of less than 0.8, insulin-dependent diabetes mellitus, erysipelas or other symptoms of clinical ulcer infections, or those with a history of cytotoxic or systemic steroid drug therapy during the last 3 months were not eligible to participate.

    Study treatments. The 10-cm x 10-cm polyurethane nonadhesive study dressing (Biatain Non-Adhesive Dressing, Coloplast A/S, Denmark) is composed of a soft, 4-mm thick hydrophilic polyurethane foam and an elastic semipermeable film backing. The 10-cm x 10-cm hydrocellular control dressing (Allevyn Hydrocellular Dressing, Smith and Nephew, England) consists of a 4-mm thick layer of soft, hydrophilic polyurethane foam bonded to a semipermeable polyurethane film. The wound contact surface of the dressing is covered with a perforated polyurethane film. At the discretion of the investigator, both dressings could be secured with a secondary absorbent dressing and an elastic bandage. The use of compression therapy, secondary dressings, and/or elastic gauze was recorded in the data collection form for each patient. Periulcer skin treatments, (eg, zinc oxide paste or topical corticosteroids) were used according to the standard procedure in the individual clinic.

   Study procedures. Subjects were randomized in blocks of six to one of the two treatment groups using sequentially numbered, sealed opaque envelopes. During the study, dressing changes involved removing the old dressing, rinsing with isotonic saline solution, and applying a new dressing. All dressings overlapped the periulcer skin by at least 1 cm from the edge of the ulcer. If necessary, a secondary absorbent dressing was applied. The compression bandage was changed once or twice a week, depending on the amount of edema and exudate. Patients were assessed upon entry into the study and every 7 days until the ulcer was completely healed or the study period of 8 weeks was completed. Dressings were changed once every 7 days, if leakage of exudate occurred, or when an interim assessment was deemed necessary. All dressing changes were recorded in the data collection form for each patient. A maximum of three clinicians per study site was responsible for the patient assessments and study procedures.

   Measurements. Healing was assessed by tracing the ulcer area and calculating the ulcer size (planimetry) and by assessing the percentage of black necrotic, yellow slough, and healthy red granulation tissue in the wound bed. The degree of exudation at baseline was assessed based on the frequency of dressing changes and exudate saturation of the dressings before entering the study. The ability of the dressings to handle exudate was assessed by recording the incidence of leakage (yes/no), number of dressing changes per week, and extent of periulcer skin reactions. Dressing absorption capacity was rated using a verbal rating scale ("excellent," "good," "reasonable," or "poor"); periulcer skin reactions (maceration, erythema, eczema, and petechiae) were assessed using a verbal rating scale ("none," "little," "moderate," or "severe"). The number of dressing changes per week was calculated by dividing the total number of dressing changes per patient by the total number of dressing changes throughout the study period, including the mandatory change at the weekly assessment. Patient comfort was evaluated by assessing the degree of smell/odor, pain, and comfort when wearing the dressing. Odor was recorded as "none," "little," "moderate," or "severe" and patients were asked to describe the experience of pain in the ulcer area as "none," "little," "moderate," or "severe." Comfort when wearing the dressing was rated as "very comfortable," "comfortable," "uncomfortable," or "very uncomfortable."

   Ethics. The study was conducted in accordance with the Helsinki Declaration and EN540. Ethics Committee approval was obtained at all study centers and all patients provided written informed consent.

   Data analysis. Data were analyzed using descriptive techniques for patient characteristics, the Student's t-test and paired Student's t-test for ulcer size, and the Mann-Whitney test for dressing absorbency variables. The incidence of leakage, need for a secondary absorbent dressing, and special treatment of the surrounding skin variables were analyzed using chi-square techniques and the Wilcoxon test, two-factor analysis of variance was used to compare number of changes per week, and log-rank Kaplan-Meier analysis techniques were used to analyze time to healing and time to complete red healthy granulation tissue data. All data analysis were performed using SPSS(R) Version 10.0 (SPSS Inc. Chicago, Ill.). Results Of the 118 patients recruited, 99 completed the study. Participants either completed the full treatment period (8 weeks), withdrew from the study after 6 weeks of care, or their ulcer healed. The mean length of the treatment was 7.0 weeks (+/- 1.7) in the polyurethane foam and 6.9 weeks (+/- 1.6) in the hydrocellular dressing group. Of the 19 patients who withdrew from the study, one withdrew consent, eight used another medication, three had protocol violations, four experienced adverse events, and three experienced serious adverse (see Table 1). A relationship between the dressings and the adverse events could not be verified. In addition, one patient in the study group developed contact dermatitis. A patch test confirmed an allergic reaction to the foam and to the hydrocellular dressing as well as to a previously used cod liver oil ointment. The maximum number of assessments for each study variable are provided in Table 2. Because not all variables were assessed at every visit as per protocol or as a result of healing, study withdrawal, or dressing not in situ, the number of assessments varies. At baseline, no significant differences between the two patient groups were observed (see Table 3). Statistical analyses of the wound area at baseline also did not show a significant difference in either the "intent to treat" (P = 0.173)or "per protocol" (P = 0.145) groups.

   Ulcer healing. Of the 53 ulcers in the study group, 18 (39%) healed. In the control group, 18 ulcers (39%) healed. The mean time to healing was 5.2 weeks (SD = 1.9) in the study group and 5 weeks (SD = 1.7) in the control group. This difference was not significant (see Figure 1). Both treatment groups showed a statistically significant decrease (study group P = 0.005, control group P less than 0.0005 in ulcer size from baseline to last week of evaluation. The mean ulcer area decreased from 5.19 cm2 to 2.01 cm2 at final evaluation in the study group and from 7.23 cm2 to 3.46 cm2 in the control group . A statistically significant decrease in relative ulcer size was noted within the two treatment groups from baseline to last week of evaluation as well (P < 0.0005 in both groups, Wilcoxon Signed Ranks test (see Figure 2). Of the 53 ulcers in the study group and the 46 ulcers in the control group, 41 and 30 (77% and 65%), respectively, developed complete healthy red granulation tissue in the study period. The mean time to the development of complete red healthy granulation tissue was 2.7 weeks (SD = 2.5) in the study group and 3.2 weeks (SD = 2.2) in the control group. This difference was not significant.

   Handling of exudate. Dressing absorbency was rated as "excellent" in 124 out of 163 (76%) of dressing changes in the study group and in 12 of 170 (7%) dressing changes in the control group (P < 0.0005, Mann-Whitney test). Leakage of exudate was observed in 198 of 309 (64%) of weekly assessments in the control group and in 172 of 355 (48%) assessments in the study group (P <0.0005, chi-square test). Use of a secondary absorbent dressing was recorded in 188 of 263 (72%) weekly assessments in the control group and in 132 of 308 (43%) in the study group (P less than 0.0005, chi-square test). The number of dressing changes per week was significantly lower in the study group (2.14) than in the control group (3.34) (P less than 0.0005, two-factor analysis of variance, log-transformation; factors were treatment and week) and the degree of periulcer skin reactions was low in both treatment groups (see Table 4). However, based on clinical judgment, special treatment of the surrounding skin was needed for 212 of the 296 (72%) dressing changes in the control group to 191 of 352 (54%) of dressing changes in the study group (P <0.0005, chi-square test).

   Patient comfort. No odor was evident in 325 of 414 (79%) dressing changes in the study group and in 246 of 355 (69%) assessments in the control group. No significant differences were observed between the two groups in patient ratings of comfort during treatment. During the weekly assessments, no pain was recorded for 226 of 379 (60%) observations in the study group and in 169 of 319 (53%) in the control group. Discussion In this study, no significant differences in healing rate or reduction of ulcer size were found between the two treatment groups. Compared to other studies, the results of this study indicate at least similar healing rates.1,4 Presumably, an extension of the study period could have shown a difference in the increase of healthy red granulation tissue. The results of this study confirm the previously reported ability of the polyurethane foam dressing to handle exudate.1,2,5 The low incidence of leakage, better absorption capacity ratings, and perceived need to protect the periulcer skin indicate effective vertical absorption and retention capacities of the polyurethane foam dressing. This may explain the lower number of dressing changes per week observed in this study. Wound exudate may damage the periulcer skin, prolonging the treatment period and adding to the patient's discomfort.6 Additionally, leakage of wound exudate can be inconvenient have a negative effect on a person's daily activities and increase costs. For example, using the observed number of dressing changes per week (study dressing 2.14; control dressing 3.34) and the material costs, the average material costs per patient per week are $10.87 for the study dressing and $18.99 for the control dressing treatment. These numbers do not include nursing time costs, an important cost in leg ulcer care.7,8 Because the study was not blinded, secondary absorbent dressing and periulcer treatments used were at the discretion of the investigator. This may have skewed the results. Furthermore, it could be argued that compression should not have been applied to patients with mixed ulcers, as compression may be contraindicated in arterial diseases. However, because the ankle/brachial index of all included patients exceeded 0.8, indicating that the ulcers have venous more than mixed etiology, applying short-stretch compression to these patients was acceptable.

Conclusion
    In this study, no significant differences in treatment outcomes between the two dressings were observed. However, compared to the hydrocellular dressing, the polyurethane foam dressing was found to have better exudate handling properties, which may explain the reduced number of dressing changes observed. Focus by healthcare authorities on controlling expenditures and ensuring access to optimum treatment necessitates that future studies address not only safety and effectiveness, but also the extenuating factors involved in the overall management of wound care.

Acknowledgment
    The authors are grateful to Coloplast A/S for funding this study and to Clinical Trial Coordinator Rikke Holt, MSc(Pharm) (Coloplast A/S) for data collection.

1. Thomas S, Banks V, Bale S, et al. A comparison of two wound dressings in the management of chronic wounds. Journal of Wound Care. 1997; 6(8): 383-386.

2. Dmochowska M, Prokop J, Bielecka S, et al. A randomized, controlled, parallel group clinical trial of a polyurethane foam dressing versus a calcium alginate dressing in the treatment of moderately to heavily exuding venous leg ulcers. WOUNDS.1999;11(1):21-28

3. Clever HU, Dreyer M. Comparing two wound dressings for the treatment of neuropathic diabetic foot ulcers. Proceedings 5th European Conference on Advances in Wound Management. Harrogate, UK. November 21-24, 1995: 201-203.

4. Kurring PA, Roberts CD, Quinlan D. Evaluation of a hydrocellular dressing in the management of exuding wounds in the community. British Journal of Nursing. 1994;3(20):1049-1053.

5. Banks V, Bale S, Harding K, Harding EF. An interim analysis of a randomized, stratified, controlled, parallel-group clinical trial of moderate to heavily exuding wounds. Proceeding from 5th European Conference on Advances in Wound Management. Harrogate, UK. November 21-24,1995;177-180.

6. Gates A. The use of a non-adherent silicone dressing in arterial leg ulceration. Journal of Wound Care. 2000;9(2):79-81.