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ear Readers: A physiologic temperature range is a vital condition for maintaining homeostasis and supporting cell function and proliferation. This concept has been the basis for “noncontact normothermic” radiant heat therapy (RHT) to support chronic wound healing. Pilot research explored the effects of 3 daily 1-hour RHT treatments on Stage III and IV pressure ulcers that were warmed to 38?C.¹ Periwound skin temperature rose during heating, while linear dimensions of the wounds significantly decreased with RHT (n = 15) versus standard care (n = 14) dressings including moist gauze and other dressings. Other researchers reported accelerated healing rates using RHT versus an alginate dressing.² A recent summary of existing evidence³ concluded that more research is needed to confirm the effectiveness of RHT on wound healing or postoperative wound infection. This month’s Evidence Corner summarizes 2 recent randomized, controlled trials that evaluate RHT when used on full-thickness pressure ulcers and provides some perspective to this puzzling literature.

RHT: A Veterans Affairs (VA) Medical Center Pilot Study on Stage III/IV Pressure Ulcers

       Reference: Kloth LC, Berman JE, Nett M, Papanek PE, Dumit-Minkel S. A randomized controlled clinical trial to evaluate the effects of noncontact normothermic wound therapy on chronic full-thickness pressure ulcers. Adv Skin Wound Care. 2002;15(6):270–276.
       Rationale: Warming increases capillary perfusion and thus may increase vascular perfusion in pressure ulcers and reduce pressure.
       Objective: This prospective, randomized, controlled study compared healing of Stage III and IV pressure ulcers managed with radiant heat therapy (RHT) to healing rates using “standard wound care” (SWC) dressings (saline-impregnated gauze, alginates, hydrogels, and hydrocolloid dressings) for up to 12 weeks.
       Methods: Of 56 subjects enrolled, those with 43 Stage III or IV pressure ulcers completed at least 3 weeks of RHT (22 ulcers) or SWC (21 ulcers) with standardized pressure relief and were included in the analysis. Subjects wore the sterile RHT cover dressing “24 hours per day, 7 days per week for 12 weeks or until wound closure.” The radiant heat element was applied and activated for 3 daily 1-hour periods, with at least 2 hours separating applications. The SWC dressing was changed daily, and the wound was irrigated with normal saline. Daily dressing changes were inconsistent with package insert instructions for some of the listed SWC dressings; thus, the comparison is of questionable clinical relevance and may not pertain to real world practice. Also, some SWC dressings listed were not as moisture retentive as the RHT cover dressing, so moisture retention and/or temperature differences may have caused the results. Measured wound outcomes included percent healed by Week 12 and change in ulcer area (cm2). Primary outcomes were not specified.
       Results: The accepted standard healing outcome, percentage of wounds closed in 12 weeks, did not differ significantly between groups. Ulcers in the SWC group were of significantly longer duration than those in the RHT group. Wound area (cm2) reduction per week was significantly greater for RHT wounds as was the average slope of the individual healing curves. These effects were reportedly greater in pressure ulcers larger than 5 cm² in wound area.
       Conclusion: The authors conclude that there is a significant effect of RHT on chronic Stage III and Stage IV pressure ulcer healing, accentuated in larger pressure ulcers.

RHT: A Multicenter Pilot Study on Stage III/IV Pressure Ulcers

       Reference: Thomas DR, Diebold MR, Eggemeyer LM. A controlled, randomized, comparative study of a radiant heat bandage on the healing of stage 3–4 pressure ulcers: a pilot study. J Am Med Dir Assoc. 2005;6(1):46–49.
       Rationale: It has been theorized that preventing hypothermia in a wound and maintaining a normothermic state might improve pressure ulcer healing.
       Objective: This prospective, randomized, controlled study explored effects of RHT versus a hydrocolloid dressing on full-thickness pressure ulcers in various settings, including outpatient clinics, long-term care, and a rehabilitation center.
       Methods: Forty-one subjects with Stage III or IV pressure ulcers on the trunk were randomized to receive either RHT therapy or a standardized moisture-retentive dressing (a hydrocolloid dressing). A calcium alginate wound filler was applied if clinically necessary. Subjects were managed for up to 12 weeks or healing, whichever came first.
       Results: Eight subjects healed in the RHT group, and 7 subjects healed in the moisture-retentive dressing group. No statistically significant difference was found between the 2 dressing regimens.
       Conclusions: A 13% difference in healing rate was reported, favorable to the RHT, but was not statistically significant at any time point in the study.

Clinical Perspective

       A genuine comparison test of healing efficacy of RHT would require a regimen using a dressing with comparable occlusive traits to the RHT dressing that is applied similarly and with the same frequency with the only variable being addition of the RHT to the dressing regimen. Much of the prior evidence has been clouded by inappropriate nomenclature, for example, calling alginates or moist gauze “moisture-retentive dressings.” Hydrocolloids and film are the only dressings with evidence that their moisture retention is comparable to the film RHT cover dressing.⁴ Composite dressings comprised of these layers may also have this capacity, but published evidence was not available. The closest comparison of RHT to a moisture-retentive dressing was the aforementioned study by Thomas et al., which showed no consistent healing advantage of the RHT over a hydrocolloid dressing. This supports the conclusion by MacFie et al.³ that there is insufficient evidence to support RHT wound healing efficacy, but it does not mean that clinicians should continue to allow wounds to cool during frequent dressing changes or by using dressings with a high moisture vapor transmission rate that permit heat loss through evaporation. For example, James⁵ noted that many modern dressings maintain higher wound surface temperatures than gauze. He summarized evidence that freshly cleansed wounds require 40 minutes to regain their original temperatures and 3 hours to restore normal mitotic and leukocyte activity. During 24 hours dressed with a hydrocolloid dressing, venous ulcer surface temperatures rose during the first 90 minutes from 32.7?C to a more physiologic wound temperature of 35.2?C and remained stable for at least 24 hours while the dressing was in place.⁶ Whitney et al.¹ reported similar rises from wound surface temperatures in RHT-treated pressure ulcers from 33.2?C to 35.6?C with the dressing in place after 1 hour of RHT treatment.
       In summary, the evidence on RHT is consistent with the interpretation that preserving physiologic wound temperature by using a moisture-retentive dressing and changing the dressing less frequently may be as effective as applying local heating to achieve healing outcomes.