A Mechanically Powered Negative Pressure Device Used in Conjunction with a Bioengineered Cell-based Product for the Treatment of Pyoderma Gangrenosum: A Case Report
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Armstrong and Lavery’s8 randomized controlled trial of 162 partial diabetic foot amputations reported that 43 (56%) of NPWT and 33 (39%) of wounds managed with standard moist wound care were healed after 112 days of treatment (P = 0.040). In a multicenter, randomized controlled trial conducted among 362 patients with diabetes and foot ulcers, Blume et al9 found NPWT to be safe and more efficacious than advanced moist wound therapy alone, achieving complete closure within the 112-day treatment phase (P = 0.007). In 2006, Vuerstaek et al10 compared NPWT to conventional wound care in the form of multilayer, short, stretch bandages in 60 hospitalized patients. They found the median time to healing was significantly less (P = 0.0001) in the NPWT treated patients compared to the conventional wound care patients with chronic leg ulcers (29 days versus 45 days). Based on their randomized controlled trial, they suggested NPWT should be considered “the treatment of choice for chronic leg ulcers owing to its significant advantages in the time to complete healing and wound bed preparation time compared with conventional wound care.”
Animal and human studies11-13 and randomized controlled trials have demonstrated the benefits of NPWT, which include increased tissue perfusion, increased granulation tissue formation, reduced bacterial load, and removal of excess interstitial edema compared to standard wound care alone. Genecov et al12 used both porcine and human models and found that split-thickness skin donor graft sites treated with NPWT epithelialized at a “much faster rate” than those treated with standard occlusive dressing.
The SNaP (Smart Negative Pressure) Wound Care System (Spiracur, Inc, Sunnyvale, CA) is a single-use, mechanically powered NPWT device that utilizes specialized springs (instead of an electric pump) to generate pre-set continuous subatmospheric pressure levels (125 mm Hg, 100 mm Hg, or 75 mm Hg) to the wound bed. Each canister maintains its preselected, continuous setting and once filled with exudate is discarded. By eliminating the electric pump, this device helps solve many of the constraints associated with traditional NPWT device use in the ambulatory setting.
Armstrong et al14 conducted a randomized controlled trial enrolling 132 patients with noninfected, nonischemic, nonplantar lower extremity wounds who were managed with the mechanically powered single use device or a battery-powered negative pressure system (V.A.C. Therapy®, KCI, San Antonio, TX). No differences in healing time, rates of healing, or number of adverse events were observed, but patient ease of use and quality of life were rated higher by subjects using the SNaP. For the primary end point (percent decrease in wound area) SNaP was found to be noninferior to NPWT at weeks 4, 8, 12, and 16 (P = 0.0030, 0.0130, 0.0051, and 0.0044, respectively). The authors also found no difference in the proportion of wounds that healed over time (P = 0.9620), an indication that SNaP worked as effectively as the comparator. The proportion of subjects experiencing device-related adverse events was similar between groups (SNaP, n = 64, comparator, n = 68) with maceration being the most common in both groups. What was significantly better in the SNaP subjects was a variety of quality-of- life indicators such as sleep disruption (P = 0.0019), comfort of wear (P <0.001), and overall satisfaction (P = 0.0009).
Bioengineered Cell-based Therapy
Bioengineered cell-based skin substitute (Apligraf, Organogenesis, Inc., Canton, MA) is a living cell-based product consisting of both dermal and epidermal layers. It is generated in vitro from neonatal foreskin and is free of contaminating cells or those that cause rejections.