Emerging Insights On Negative Pressure Wound Therapy

Karen Shum, DPM, and Kazu Suzuki, DPM, CWS

   Although NPWT dressing changes have traditionally occurred three times a week (i.e. Monday/Wednesday/Friday), we have found that twice-a-week dressing changes (i.e. Monday/Thursday or Tuesday/Friday) may be as effective while alleviating the pain and the logistical cost to our patients. Pain and quality of life measurements are superior in patients with lower extremity leg ulcers who have undergone NPWT in comparison to conventional therapy as they are on less bed rest and are able to ambulate earlier with NPWT.15

Assessing The Benefits Of Different NPWT Devices

Now that there are multiple NPWT devices on the U.S. market, our options have expanded greatly and include different types of dressing interfaces (polyurethane foam vs. gauze), battery-powered vs. mechanically-powered suction, and small disposable devices versus larger rental devices.

   The debate over the effectiveness of improved granulation tissue formation between foam and gauze has so far occurred with porcine models. Studies have evaluated wound contraction and microvascular blood flow within the tissue and showed similar results when comparing foam and gauze.2,13 In biopsies of the wound bed, there is evidence of tissue pulling through foam and gauze space, signaling granulation tissue formation and reduction in wound surface area with the two separate dressing interfaces.14 In our institution, we prefer polyurethane foam dressing as gauze dressings may disintegrate faster and the gauze fragments may be embedded within the wound bed.

   The introduction of simple, smaller, portable devices on the market has now enabled the care of wounds via NPWT on an outpatient basis at home or in a skilled nursing facility. This ultimately reduces the length of hospitalization with a decrease in overall medical cost and simplifies delivery and care logistics.16

   SNaP (Spiracur) is a small NPWT device that is lightweight (2.2 oz) and mechanically powered (“non-powered”) in comparison to the widely-used ActiVac Therapy System (KCI), which is electrical with a rechargeable battery. SNaP functions with metal springs that generate continuous negative pressure therapy and is designed to be single-use and disposable as the canister for the wound fluid is integrated within the device.

   A multicenter, comparative, randomized control trial evaluated SNaP and VAC therapy in healing lower extremity wounds and showed comparable results in patients treated for diabetic foot ulcers and venous ulcers.17 In our clinical experience, the clinical efficacy of NPWT has been equivalent for both devices as long as the pressure settings and the dressing interface are the same.

   The smaller design of the SNaP has a distinct advantage in that one may apply the small form and light weight for most wound care patients, including older, frail patients, who may find traditional battery-operated devices to be heavy. The aforementioned randomized controlled study found that the SNaP system interferes significantly less with overall activity, sleep and social interaction than the VAC therapy system.17 On the other hand, because of its small canister capacity, the SNaP device may not be suitable in cases that require a large amount of wound drainage, for example, for the treatment of large venous leg ulcers.

A Pertinent Overview On Clinical Uses Of NPWT

Negative pressure wound therapy is an adjunctive therapy to improve wound healing in the field of surgery and wound care. As with any other wound dressing, it is imperative to make sure the wound is free of ischemia and infection before the application of NPWT dressings.

   In our institution, we use a laser Doppler machine (SensiLase, Vasamed) to measure skin perfusion pressure (SPP) and pulse volume recordings (PVRs) to rule out ischemia in lower extremities. In grossly infected wounds, purulence clogs the open pores of NPWT foam dressings. Physicians should not use NPWT in such patients until they can debride and decontaminate the wound sufficiently in the operating room along with appropriate administration of antibiotics.

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