Negative-Pressure Wound Therapy

The purpose of negative-pressure wound therapy is to apply controlled subatmospheric (negative) pressure to the wound bed for stimulation of granulation tissue and edema reduction, and thus, enhancement of wound healing.

PREREQUISITE NURSING KNOWLEDGE

• Negative-pressure wound therapy (NPWT) is an advanced wound care therapy that uses an occlusive wound dressing, tubing, and powered vacuum unit with a collection canister. Other terms found in the literature for NPWT include topical negative therapy (TPN) and subatmospheric pressure therapy.

• Many different U.S. Food and Drug Administration (FDA)–approved vacuum units are on the market for NPWT.¹⁰ The Agency for Healthcare Research and Quality (AHRQ) provides a review of current NPWT manufacturers.¹¹ The most common devices seen in the acute care practice setting are ActiV.A.C.® and InfoV.A.C. Therapy Systems (KCI Licensing, Inc., San Antonio, TX; Fig. 131-1) and RENASYS EZ® (Smith & Nephew, St. Petersburg, FL⁸; Fig. 131-2). ActiV.A.C.® and Info V.A.C.®¹² use a patented open-cell foam wound contact dressing, and RENASYS EZ®⁶ (and other newly developing units on the market) uses either an open-cell foam or the vacuum-pack method with an antimicrobial gauze packing dressing. The use of moistened gauze wound interface has also been reported in the literature as an effective dressing for NPWT.⁷

Figure 131-1 Components of the Vacuum-Assisted Closure System: ActiV.A.C.® and InfoV.A.C.® Therapy Systems. (Courtesy of KCI Licensing, Inc. 2009.)

Figure 131-2 Components of RENASYS EZ® NPWT therapy. (Courtesy of Smith & Nephew, Inc.)

• Most randomized controlled studies and case studies on NPWT have been conducted with the V.A.C. therapy. No randomized controlled trials are found that compare the effectiveness of various NPWT techniques or systems.¹¹ Further clinical research to evaluate wound closure outcomes with the different NPWT units is needed.⁵^,⁸^,¹⁰^,¹¹

• NPWT assists with wound closure by applying a controlled subatmospheric (negative) pressure evenly over a wound bed. This mechanical stress creates a noncompressive force on the wound bed that dilates the arterioles, increasing the effectiveness of local circulation and enhancing the proliferation of granulation tissue.¹^,⁴^,⁵ NPWT enhances lymphatic flow and removal of excessive fluid, decreasing wound edema and bacterial load at the wound site, further aiding wound healing (Fig. 131-3).¹^,²^,⁴^,⁵^,⁹^,¹⁰

Figure 131-3 ActiV.A.C.® and InfoV.A.C.® Therapy Systems. Fluid, exudate, and debris removed from wound bed. (Courtesy of KCI Lincensing, Inc. 2009)

• Wound healing is best achieved through adequate cleansing, débridement, and dressing of the wound bed on the basis of patient and wound characteristics.

• Wounds heal by either primary or secondary intention (see Fig. 126-1). Most clean surgical wounds heal by primary intention. Suturing each layer of tissue approximates the wound edges. These wounds typically heal quickly and require minimal wound care. Contaminated surgical or traumatic wounds (open wounds) heal by secondary intention. Wounds that heal by secondary intention granulate from the base of the wound to the skin surfaces; care must be taken to allow for uniform granulation and prevention of open pockets or tunneling.