Prologue

Abstract

In May 2011, an international panel of wound care experts from multiple disciplines convened to develop this document to summarise the evolution of negative pressure wound therapy (NPWT) technology devices over the past 15 years, specifically concentrating on the V.A.C.^® Therapy (KCI USA, Inc., San Antonio, TX) family of products. The aim of this document, which will be comprised of six articles, is to describe appropriate use of current technology options across a variety of wound types. The articles will include literature reviews, initiation criteria, treatment outcomes, technical pearls and clinical cases that will show the enhanced outcomes and potential economic value of the various NPWT technologies in use today.

DEFINITION AND HISTORY OF NEGATIVE PRESSURE WOUND THERAPY

Over the last 30 years, there have been tremendous advances in the science of wound care based on a growing understanding of the physiology of wound healing and subsequent patient optimisation techniques now being used by clinicians. For the past 15 years, parallel advances in the understanding and technology of negative pressure wound therapy (NPWT) have occurred. NPWT is the controlled application of subatmospheric pressure to a wound surface using an electrical or battery‐powered pump to intermittently or continuously deliver subatmospheric pressure through a dressing and remove effluent, thereby promoting wound healing.

Extending back to 400 BC in ancient Greek writings, NPWT applied through ‘cupping’ with various plant‐derived cup‐shaped devices has been used to extract toxins, such as venom and infectious drainage from wounds (1). This practice spread throughout the Roman Empire and descriptions of cupping appeared throughout what is now Asia and Europe until the last century. With a new focus on tissue repair evolving from an increased understanding of moist wound healing, researchers developed closed‐suction treatment techniques during the mid‐20th century (2). Closed suction meant that the wound was sealed, enabling true subatmospheric pressure in a natively moist environment (3). In the 1980s, Russian researchers studied various gauze dressings and suction devices via surgically inserted hollow tubes. The results of these early studies showed that using negative pressure after wound debridement helped to control infection in the wound, and thus aided the healing process 4, 5.

The first commercialised NPWT device (V.A.C.® Therapy, KCI USA, Inc., San Antonio, TX) was introduced in 1996 for general use in chronic, subacute, and acute wounds, and over flaps or grafts. This system employed a reticulated open‐cell foam (ROCF; V.A.C.® GranuFoam™ Dressing, KCI USA, Inc., San Antonio, TX) as the interface between the subatmospheric pressure source and the wound bed. Evaluation of this NPWT/ROCF system in the clinical setting immediately followed (6). In 1997, a comprehensive scientific development study was published regarding the use of NPWT/ROCF by Morykwas and colleagues (7). This study showed the clearance of infectious material from the wound, as well as the positive effects on local blood flow, granulation tissue formation and wound closure with the use of NPWT/ROCF (7).

MECHANISMS OF ACTION OF NPWT

Two broad mechanisms of action have been proposed to account for the promotion of wound healing seen with NPWT/ROCF: a biological tissue response (microstrain) 8, 9, 10 and a mechanical tissue response (macrostrain) 11, 12, 13 (Figure 1). Microstrain occurs when negative pressure draws wound bed tissue into the open pores of the ROCF dressing, and macrostrain develops when negative pressure contracts the wound bed around the ROCF dressing. These mechanisms have been found to produce several wound bed physiological changes that account for healing (Table 1).

Figure 1.

NPWT mechanisms of action. (Reprinted with permission from KCI licensing, Inc.).

Table 1.

Mechanisms of action of NPWT/ROCF

Microstrain	Macrostrain
• Creates tissue microdeformation that leads to cell stretch	• Draws wound edges together
	• Removes infectious material and wound fluids
• Causes cell stretching that may increase metabolic activity, fibroblast migration, cellular proliferation and extracellular matrix production
	• Reduces oedema
	• Promotes perfusion

NPWT, negative pressure wound therapy; ROCF, reticulated open‐cell foam.

The healing mechanisms of NPWT/ROCF are based on the assumption that uniform subatmospheric pressure exerts a mechanical stress on the wound bed. This stress is transmitted to the cytoskeleton, resulting in the activation of signal transduction pathways, which trigger cell recruitment, growth factor expression and cell proliferation 8, 9, 10, 14, 15. The growth of granulation tissue is stimulated as a result, and wound healing may follow at a faster rate than that seen with the application of moist wound healing dressings (16).

Studies have shown that NPWT may stimulate angiogenesis and a three‐ to fivefold increase in cutaneous blood flow adjacent to the wound edges 17, 18. This increases the availability of oxygen and chemical substrates needed for tissue regeneration (19). The application of negative pressure has the added benefit of removing wound exudate and infectious material, which may decrease local oedema 20, 21. By removing pro‐inflammatory cytokines and matrix metalloproteinase, negative pressure helps create a favourable healing environment 22, 23.

A variety of clinical goals and endpoints for NPWT/ROCF use based on the World Union of Wound Healing Society Principles of Best Practice document (24) are summarised in Table 2.

Table 2.

Clinical goals and endpoints of NPWT/ROCF

NPWT/ROCF clinical goals and endpoints

• Reduce wound volume where there has been tissue loss

• Promote granulation tissue formation

• Reduce wound surface area with edge contraction

• Remove wound exudate

• Reduce oedema

• Increase the vascularity of a wound in preparation for a reconstructive procedure

• Reduce the complexity of future surgical reconstruction

• Remove bacterial bioburden in a wound

• Minimise contamination of an open wound with the dressing barrier

• Decrease frequency of wound dressing changes

NPWT, negative pressure wound therapy; ROCF, reticulated open‐cell foam.

INDICATIONS, CONTRAINDICATIONS AND WARNINGS FOR NPWT/ROCF USE

The ActiV.A.C.®, InfoV.A.C.®, V.A.C. ATS®, V.A.C. Freedom® and V.A.C.Via™ Therapy Systems are integrated wound management systems for use in acute, extended and homecare settings. The NPWT/ROCF products listed above are indicated for patients with chronic, acute, traumatic, subacute and dehisced wounds, partial thickness burns, ulcers (e.g. diabetic, pressure and venous insufficiency), flaps and grafts.

Table 3 lists the contraindications for these NPWT/ROCF products. It is important to read and follow all instructions and safety information prior to use for any NPWT device. NPWT/ROCF should be used cautiously when there is active bleeding, when the patient is on anticoagulants or platelet aggregation inhibitors, when there is difficult wound haemostasis, or when placing the dressing in proximity to infected blood vessels. Additional precautions include using NPWT/ROCF when there is difficulty in maintaining a seal, painful wounds and evidence of previous patient nonadherence to therapy (25). For a complete listing of all warnings, precautions and contraindications, please refer to appropriate clinical guidelines and/or product labelling (26).

Table 3.

Contraindications of NPWT/ROCF

Contraindications to NPWT/ROCF include, but may not be limited to:

• Use of foam dressing in direct contact with exposed vital organs (blood vessels, anastomotic sites, organs or nerves)

• Non‐enteric and unexplored fistulas

• Inadequately debrided wounds with necrotic tissue with eschar

• Untreated osteomyelitis within the wound

• Presence of untreated coagulopathy

• Malignancy in the wound

• Sensitivity to silver

NPWT, negative pressure wound therapy; ROCF, reticulated open‐cell foam.

The clinical impact of NPWT technology evolution

This document combines expert opinion with scientific evidence to describe the use of V.A.C.® Therapy family of products in patients with pressure ulcers, diabetic foot and venous leg ulcers, open abdomens, surgical incisions, and in support of skin grafts and flaps. Table 4 describes the V.A.C.® Therapy family of products discussed in the subsequent articles.

Table 4.

NPWT devices

NPWT device	Clinical use	Advancement
V.A.C.® Therapy System	Chronic, acute, traumatic, subacute and dehisced wounds, partial thickness burns, ulcers (e.g. diabetic, pressure and venous insufficiency), flaps and grafts	First commercially available NPWT device that employed a conforming reticulated open‐cell foam interface drastically different from gauze; SensaT.R.A.C.™ Technology that measures and compensates for pressure variances at the wound site
ABThera™ Open Abdomen Negative Pressure Therapy System	Acute, open abdomen with exposed viscera	Dedicated NPWT system to manage open abdomen; larger canister size; specific dressing designed to manage fluid and draw wound edges together
V.A.C.ULTA™ Therapy System	Indicated for all wound types [i.e. chronic, acute, traumatic and dehisced wounds, ulcers (e.g. diabetic, pressure and venous insufficiency)] that would benefit from instillation of topical wound cleansers or solutions, such as wounds at risk for compromised healing	NPWT coupled with volumetric automated fluid instillation and removal of topical wound treatment solutions; dressings specifically designed to optimise the benefits of instillation therapy
Prevena™ Incision Management System	Clean, closed incisions	Ultra‐lightweight, disposable, for‐purchase NPWT device; integrated peel‐and‐place dressing with skin interface layer specifically designed for easy placement over closed incisions
V.A.C.Via™ Therapy System	Ambulatory use for post‐graft, or wounds ≤250 cm3 and exudate volume of 80 cc or less per day; transitioning patients out of acute facilities	Simple, portable, convenient ultra‐lightweight, disposable, for‐sale NPWT device

NPWT, negative pressure wound therapy.

ACKNOWLEDGEMENTS

I would like to thank Julissa Ramos, PhD (KCI, Inc.) for assisting with preparation of the manuscript.

CONFLICTS OF INTEREST

Dr SG has a consulting agreement with Kinetic Concepts, Inc. for the development of this article. This article is part of an educational supplement funded by Kinetic Concepts, Inc. to provide an overview of the V.A.C.® Therapy family of products for new users in developing markets. This supplement is targeted for distribution at the 2012 World Union of Wound Healing Societies (WUWHS) conference.