SNaP® Wound Care System Made Easy
22/02/12 | Complex wounds, Wellbeing and concordance | Piaggesi A, Ivins N, Gibbons G, Fong K.
The treatment of wounds with negative pressure wound therapy (NPWT) has revolutionised practice over the past decade. However, implementation of therapy can be a difficult process for both clinicians and patients —conventional NPWT devices often require a lengthy procurement process to obtain rental units, and complex dressing applications. This document discusses the use of the SNaP® Wound Care System (Spiracur Inc, Sunnyvale, USA), an ultraportable NPWT system for ambulatory and active patients. This system is easy to use, accessible, and may allow earlier discharge from hospital, helping to reduce costs and improve quality of life.
Using conventional NPWT systems
NPWT offers an important option for the advanced management of many wound types and has the potential to benefit a large number of patients[1,2]. The role of NPWT therapy is well established; however, for patients who are ambulatory and active, conventional NPWT pumps can be bulky and intrusive to use, require electrical plug-ins or use battery power, and create noise that is often embarrassing in social situations and may interfere with sleep. Furthermore, these conventional systems are expensive and are not optimised for the typically smaller sized wounds seen in the ambulatory outpatient setting.
Why the SNaP System was developed?
The SNaP Wound Care System was developed at the Biodesign Innovation Program at Stanford University in Palo Alto, California, USA. The key insight that led to its development was that many of the chronic wounds that could benefit from NPWT, such as diabetic foot ulcers and venous leg ulcers, are relatively small in size[3,4]. The SNaP System was therefore designed specifically for small-to-medium sized, slow-to-heal wounds.
The goal was to create a NPWT device that was easy to use by both clinicians and patients. Specifically, the device should be one that clinicians could take off the shelf like any other wound care dressing, was quick and easy to apply, and that patients could wear under their clothes and would not impinge on normal activities. The idea was to make it practical and cost-effective, allowing more patients to benefit from NPWT in the outpatient setting.
How does the SNaP System work?
The SNaP System (see Figure 1) is a disposable, ultraportable NPWT device that does not require an electrically- or battery-powered pump. The SNaP System is a mechanically-powered NPWT system comprising spring technology that reduces air density within an enclosure in a controlled manner. The specialised springs equilibrate even in the presence of exudate so that a constant controlled amount of negative pressure is delivered to the wound bed. Because there is no electrical pump, operation of the SNaP System is completely silent, and it is small enough to be worn on a patient's leg, arm, or belt and hidden under everyday clothing.
The SNaP Wound Care System consists of three basic elements:
- The cartridge with activation/reset key
- Hydrocolloid dressing layer with integrated nozzle and tubing and choice of foam or antimicrobial gauze wound interface layer
- Strap with attachment clip.
The cartridge is currently produced with three different pre-set pressure levels (-75mmHg, -100mmHg and -125mmHg). The cartridge portion of the device weighs 62.3g (2.2oz) and has a canister capacity of approximately 60mL of wound exudate. A visual indicator signals if the canister is full of exudate or if there is an air leak. The SNaP System also incorporates BioLock® technology that isolyzes or gels the wound exudate that collects in the cartridge. This helps to control potential contamination and odour.
A proprietary hydrocolloid dressing provides protection to the often friable periwound skin, improves dressing application handling properties, and provides a robust seal around the wound for negative pressure delivery. The suction port and tubing (which can be cut to length) are fully integrated into the hydrocolloid dressing, simplifying the application process.
The hydrocolloid dressing is used over a wound filling material consisting of a specialised SNaP® BLUE foam dressing or antimicrobial gauze dressing (Kendall™ AMD gauze dressing, Covidien).
The BLUE foam dressings allows for similar mechanical transduction of stress and strain to the wound bed as other foam wound interfaces. The bright blue colour of the foam dressing also allows for easy visualisation within the wound, helping to prevent retention of the foam at dressing changes. In general, the foam dressing is used when more robust granulation tissue formation is required or in deeper wounds. The antimicrobial gauze dressing is used in more superficial wounds or in wounds at higher risk of infection.
The BLUE foam dressing and antimicrobial gauze can be used in conjunction with commercially available wide mesh non-adherent base layers that prevent ingrowth or provide additional antimicrobial action. It is important that careful consideration is given to the use of a base layer prior to application to ensure optimal delivery of negative pressure to the wound bed.
How does the level of negative pressure provided compare?
Both the electrically-powered and the disposable, mechanically-powered NPWT devices achieve the same air density reduction. This results in the delivery of identical negative pressure by both mechanisms at the level of the wound bed (see Figure 2).
To validate this, pre-clinical bench-top and animal studies were performed at Stanford University that demonstrated equivalent delivery of NPWT and equivalent wound healing between the SNaP Wound Care System and the V.A.C.® Therapy™ System (an electrically-powered NPWT device manufactured by KCI, San Antonio, Texas) and other electrically-powered pumps[6,7].
In addition, clinical trial data has shown equivalent outcomes to electrically-powered NPWT devices. In a case series of 63 patients with diabetic and venous ulcers, Lerman et al8 found that the SNaP System resulted in a 50% improvement in time to healing. This was further supported by a multicentre randomised controlled trial (RCT) comparing the outcomes of the SNaP System and the V.A.C. Therapy System in 132 patients with lower extremity diabetic and venous ulcers. The two systems gave similar outcomes in terms of wound healing[9,10], while superior results were shown for the SNaP System in terms of quality of life.