Warm-Up® Active Wound Therapy (Augustine Medical, Inc., Eden Prairie, MN), also known as noncontact normothermic wound therapy (NNWT) uses a non-contact radiant-heat bandage to treat chronic venous ulcers when conventional wound-healing therapy has failed. The device consists of a noncontact, domed wound cover into which a flexible infrared heating card is inserted. A battery pack powers the device and warms the wound to a pre-determined temperature. The inside of the wound cover contains a foam ring, which acts as a wick to drain away exudate.
In a Decision Memorandum, the Center for Medicare and Medicaid Services (CMS) reviewed the evidence of the effectiveness of noncontact normothermic wound therapy. The CMS concluded that “the medical literature does not support a finding that NNWT heals any wound type better than conventional treatment.” CMS concluded, therefore, that there is insufficient evidence in the peer-reviewed medical literature to consider this device as reasonable and necessary for the treatment of wounds.
An assessment of treatments for chronic pressure ulcers by the Ontario Ministry of Health and Long-Term Care (2009) concluded that "thermal dressings such as noncontact normothermic dressings or radiant heat dressings were associated with greater improvement in stage III and IV pressure ulcers; however, this did not translate into more wound closure. There is no evidence at present to conclude that thermal dressings will result in more complete healing in stage III or IV pressure ulcers."
Several recent studies have evaluated the effectiveness of NNWT for the treatment of chronic wounds. However, there are drawbacks from these studies -- small sample sizes and lack of long-term follow-up. McCulloch and Knight (2002) examined the effect of a noncontact, radiant warming device in the treatment of neuropathic foot wounds secondary to diabetes. Patients (n = 36) were assigned to management with off-loading and warming (treatment) or off-loading therapy only (control) for a period of 8 weeks or until healing. Wounds of subjects in the treatment group healed at a rate of 0.019 +/- 0.019 cm2/day compared with that of 0.008 +/- 0.009 cm2/day in the control group (p = 0.049). The difference between treatment and control groups barely reached statistical significance.
The authors of a small (13 patients) preliminary study on Warm-Up® Active Wound Therapy concluded that Warm-Up® Active Wound Therapy is a safe treatment modality for chronic venous stasis ulcers; however, further investigation using a larger prospective study is needed to demonstrate effectiveness
Kloth and associates (2002) studied the effect of NNWT versus standard wound care on patients (n = 40) with 43 stage III and IV pressure ulcers. A sterile noncontact wound dressing was applied to 21 wounds for 24 hours per day, 7 days per week. Each day after the wound was irrigated and the noncontact dressing was changed, a heating element in the dressing was activated for 3 1-hour periods for 12 weeks or until wound closure. Twenty-two control wounds were treated with standard, moisture-retentive dressings 24 hours per day, 7 days per week for 12 weeks or until wound closure. The healing rate for the treatment group was significantly greater than that for the control group (0.52 cm2 per week and 0.23 cm2 per week, respectively; p < 0.02). However, the difference in the incidence of closure among wounds that completed the entire 12-week protocol between treatment and control groups were not significant (11 of 14 or 78.5 % for the treatment group and 8 of 16 or 50 % for the control group).
In a pilot study, Karr (2003) studied the use of NNWT in the treatment of wounds associated with osteomyelitis. This study consisted of 2 arms: (i) the control arm (11 patients with 11 ulcers) received standard wound care, and (ii) the treatment arm (5 patients with 6 ulcers) received NNWT. Standard wound care resulted in complete ulcer healing at an average of 127 days, while NNWT resulted in complete ulcer healing at an average of 59 days, or 54 % faster than in the control arm. However, the mean wound healing times between the 2 groups were not significantly different (p < 0.33). Moreover, the median wound healing time for the 2 groups were quite similar (70 days for the control group and 68 days for the treatment group). The authors concluded that a larger prospective study that evaluates NNWT for ulcers associated with osteomyelitis is warranted.
In a prospective, randomized, controlled study, Alvarez and colleagues (2003) compared diabetic foot ulcer healing in patients being treated with either NNWT applied for 1 hour 3 times daily until healing or 12 weeks, or standard care (saline-moistened gauze applied once-daily). Surgical debridement and adequate foot off-loading was provided to both groups. Evaluations were performed weekly and consisted of acetate tracings, wound assessment, and serial photography. A total of 20 patients completed the study and both treatment groups were distributed evenly (n = 10). Ulcers treated with NNWT had a greater mean percent wound closure than control-treated ulcers at each evaluation point (weeks 1 to 12). After 12 weeks, 70 % of the wounds treated with NNWT were healed compared with 40 % for the control group. However, the differences were not significant (p < 0.069). The authors concluded that further study in a greater patient population is needed to assess the effectiveness of NNWT in treating neuropathic foot ulcers.
In a randomized controlled study, Thomas et al (2005) examined the effectiveness of radiant heat bandage on the healing of stage 3 or stage 4 pressure ulcers. A total of 41 subjects with a stage 3 or stage 4 truncal pressure ulcer greater than 1.0 cm2 were recruited from outpatient clinics, long-term care nursing homes, and a rehabilitation center. The experimental group was randomized to a radiant-heat dressing device and the control group was randomized to a hydrocolloid dressing, with or without a calcium alginate filler. Subjects were followed until healed or for 12 weeks. Eight subjects (57 %) in the experimental group had complete healing of their pressure ulcer compared with 7 subjects (44 %) with complete healing in the control group (p = 0.46). The authors noted that although a 13 % difference in healing rate between the 2 arms of the study was found, this difference was not statistically significant.
In a single center randomized study with 49 patients, Alvarez et al (2006) reported that NNWT improves the healing of diabetic neuropathic foot ulcers. Moreover, these researchers stated that further study in a greater patient population is needed to fully assess the effectiveness of this device and to provide additional information on whether local warmth can reduce the incidence of infection.
Serena et al (2009) examined if noncontact, nonthermal, low-frequency ultrasound (LFU) therapy is effective in controlling wound bacterial colony counts in a series of 4 related experiments. First, ultrasound penetration in both wounded and intact skin was assessed in-vitro. Compared to sham, noncontact ultrasound penetrated farther into both wounded (3.0 to 3.5 mm versus 0.35 to 0.50 mm) and intact (2.0 to 2.5 mm versus 0.05 to 0.07 mm, respectively) pig skin. Second, using an in-vitro model to stain and count live/dead bacteria, 0 % of sham-treated and 33 % of Pseudomonas aeruginosa, 40 % of Escherichia coli and 27 % of Enterococcus faecalis were dead after 1 ultrasound application. Minimal effects on methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus were observed. Third, using an in-vivo model, after 1 week, while differences between different bacterial species were observed, overall bacterial quantity decreased with ultrasound treatment (from 7.2 +/- 0.79 to 6.7 +/- 0.91 colony forming units [CFU] per gram of tissue [CFU/g]) and silver anti-microbial dressings (from 7.2 +/- 0.79 to 5.7 +/- 0.6 CFU/g) but increased to 8.6 +/- 0.15 CFU/g for sham and 8.6 +/- 0.06 CFU/g for water-moistened gauze. Fourth, 11 patients (average age of 60 years) with pressure ulcers containing bacterial counts greater than 10(5) CFU/g of tissue received 2 weeks of noncontact ultrasound therapy. The quantities of 7 bacterial organisms were reduced substantially from baseline to 2 weeks post-treatment. None of the wounds exhibited signs of a clinical infection during the treatment period and no adverse events were observed. Taken together, these 4 studies indicated that noncontact ultrasound can be used to reduce bacterial quantity. The authors concluded that controlled clinical studies are needed to determine the effectiveness of this treatment and to further elucidate its effects on various Gram-negative and Gram-positive bacteria.
In an in-vitro study, Conner-Kerr and colleagues (2010) examined the effects of LFU delivered at 35 kHz on bacterial viability, cell wall structure, and colony characteristics, including antibiotic resistance on vegetative forms of MRSA. They concluded that studies to elucidate the observed effects of LFU on MRSA and evaluate its effect in-vivo are needed. Furthermore, in a Cochrane review on therapeutic ultrasound for venous leg ulcers, Cullum et al (2010) concluded that the studies evaluating ultrasound for venous leg ulcers are small, poor-quality and heterogeneous. There is no reliable evidence that ultrasound hastens healing of venous ulcers. There is a small amount of weak evidence of increased healing with ultrasound, but this requires confirmation in larger, high-quality randomized controlled trials. There is no evidence of a benefit associated with LFU.