A Guide To Current And Emerging NPWT Modalities

Adam Isaac, DPM, and David G. Armstrong, DPM, PhD, MD

   Various authors have reported the use of NPWT over closed incision sites in cases of coronary artery bypass grafting, abdominal hysterectomy, revisional hip arthroplasty, transmetatarsal amputation and high-risk fractures of the lower extremity.21-23 Researchers have reported using a pressure setting of 75 to 125 mmHg, typically applying a non-adherent dressing between the incision site and foam layer. The Prevena™ Incision Management System (KCI) is a device specifically designed for applying NPWT over closed incision sites. The compact system has a 45 mL canister and includes a semi-permeable incision dressing impregnated with ionic silver.24

   In a prospective, randomized, multicenter clinical trial published in 2012, Stannard and co-authors were able to demonstrate a decreased incidence of wound dehiscence and infection in postoperative tibial plateau, pilon and calcaneal fractures treated with closed incision NPWT.23 In this study based on 249 patients, with an even distribution of 263 tibial plateau, pilon and calcaneal fractures, the authors found that the relative risk of developing an infection was 1.9 times higher in patients treated with standard postoperative dressings in comparison to those receiving closed incision NPWT.

Does Portable NPWT Offer Healing Promise For Smaller Wounds?

Another recent breakthrough in NPWT has been the development of the Smart Negative Pressure (SNaP®) Wound Care System (Spiracur), a novel portable device that utilizes specialized springs to deliver NPWT without the need for an electrically powered pump. In contrast to the electrically powered NPWT systems, the SNaP System is designed for smaller wounds and is fully disposable. The system is silent throughout its operation and is readily available for “off-the-shelf” use, obviating the need for costly and time-consuming rental agreement. The patient may wear the device, roughly the size and weight of a cell phone, beneath his or her clothing. The SNaP system consists of a cartridge, a hydrocolloid dressing layer with an integrated nozzle and tubing, and a wound interface layer made of either foam or gauze. The cartridge, which doubles as the storage canister (60 mL capacity), can deliver negative pressures of 75, 100 and 125 mmHg.25-27

   In a prospective, multicenter, randomized controlled study, Armstrong and colleagues compared the SNaP Wound Care System to the VAC therapy system for the treatment of chronic lower extremity wounds.28 Over a period of 16 weeks and in 17 study centers, 115 patients with non-infected, non-ischemic, non-plantar lower extremity diabetic and venous wounds received treatment with either the SNaP System or the VAC therapy system. The results showed that at four, eight, 12 and 16 weeks, with respect to percent decrease in wound area, the patients treated with the SNaP system demonstrated non-inferiority to the patients treated with VAC therapy.

   Furthermore, the study authors reported that the effect of the SNaP system in promoting complete wound closure was not significantly different than VAC therapy. The mean application time for the SNaP system was significantly shorter than that for VAC therapy, and patients treated with the SNaP system reported improved activities of daily living, less interruption in sleep and better comfort in social situations.

   A battery-powered version of the KCI device (VAC Via) is also available with the intention of providing a smaller form factor like the non-electrically-powered SNaP device.

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