Negative pressure wound therapy

Negative Pressure Wound Therapy (NPWT) is the use of sub-atmospheric pressure to promote or assist wound healing, or to remove fluids from a wound site.

Introduction

Negative Pressure Wound Therapy has two forms which mainly differ in the type of dressing used to transfer NPWT to the wound surface (foam or gauze). One was developed by Dr. Louis Argenta and Dr. Michael Morykwas from Wake Forest University School of Medicine. Their early animal research studied the effect of sub-atmospheric pressure on blood flow to the wound area, removal of bacteria from the wound site, and rates of granulation tissue formation. They published three landmark articles regarding these studies in 2001, in which they describe a system of sub-atmospheric pressure delivery to the wound site utilizing a sealed polyurethane foam dressing attached by a tube to a vacuum pump.

The second was developed by Dr. Mark E. Chariker and Dr. Katherine F. Jeter in 1989. Their work at Spartanburg Regional Medical Center in Spartanburg, South Carolina detailed the use of a Jackson-Pratt drain wrapped in gauze with a transparent dressing placed over the top. The tubing was then connected to wall suction to increase granulation and reduce exudate in the wound bed. The method came to be known as the Chariker-Jeter technique, which started being commercially marketed in 2001 under the Blue Sky Medical Group.

Currently there are two primary suppliers of NPWT systems in the medical industry. KCI, San Antonio, TX, uses the patented V.A.C. (Vacuum Assisted Closure) system described by Morykwas and Argenta, and Blue Sky, Carlsbad, CA, utilizes the patented Versatile 1 Wound Vacuum System with the Chariker-Jeter technique.

Clinical Evidence

Evidence based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients. [Sackett, D.L., Rosenberg, W.M., Gray, J.A., Haynes, R.B., & Richardson, W.S. Evidence based medicine: what it is and what it isn't. BMJ 312, 71-72 (1996).] A growing body of clinical evidence that includes more than 300 peer-reviewed articles [Hunter, J.E., Teot, L., Horch, R., & Banwell, P.E. Evidence-based medicine: vacuum-assisted closure in wound care management. Int. Wound J. 4, 256-269 (2007)] including over a dozen randomized controlled trials (RCTs) [Andros, G. et al. Consensus statement on negative pressure wound therapy (V.A.C. Therapy) for the management of diabetic foot wounds. Ostomy Wound Manage. Suppl, 1-32 (2006).] studying the clinical outcome when treating patients with NPWT exists. Current evidence is mainly derived from studies utilizing the V.A.C. therapy system and all higher evidence (SIGN, level 1) [Harbour, R. & Miller, J. A new system for grading recommendations in evidence based guidelines. BMJ 323, 334-336 (2001).] is exclusively derived from studies with this system, as the newer system has yet to be more fully investigated. [Kirby, M. Negative Pressure Wound Therapy. The British Journal of diabetes and vascular disease 7, 230-234 (2007).]

Earlier studies that investigated the efficacy of NPWT were in general small and often had serious methodological flaws. [Evans, D. & Land, L. Topical negative pressure for treating chronic wounds: a systematic review. Br. J. Plast. Surg. 54, 238-242 (2001).] In recent years however several larger and better designed RCTs comparing NPWT with alternative modern wound dressings were published. [Armstrong, D.G. & Lavery, L.A. Negative pressure wound therapy after partial diabetic foot amputation: a multicentre, randomised controlled trial. Lancet 366, 1704-1710 (2005).] [Vuerstaek, J.D. et al. State-of-the-art treatment of chronic leg ulcers: A randomized controlled trial comparing vacuum-assisted closure (V.A.C.) with modern wound dressings. J. Vasc. Surg. 44, 1029-1037 (2006).] [Blume, P.A., Walters, J., Payne, W., Ayala, J., & Lantis, J. Comparison of Negative Pressure Wound Therapy Utilizing Vacuum-Assisted Closure to Advanced Moist Wound Therapy in the Treatment of Diabetic Foot Ulcers A Multicenter Randomized Controlled Trial. Diabetes Care(2007).] Two of these RCTs studied the clinical outcome of NPWT in diabetic foot wounds. Another RCT studied the effects of NPWT in chronic leg ulcers. [Vuerstaek, J.D. et al. State-of-the-art treatment of chronic leg ulcers: A randomized controlled trial comparing vacuum-assisted closure (V.A.C.) with modern wound dressings. J. Vasc. Surg. 44, 1029-1037 (2006).] All three studies concluded that NPWT is safe and results in significantly faster wound healing when compared to control therapies.

In the past decade several authors have developed systematic reviews evaluating the available evidence. [Iheanacho I Topical Negative Pressure for chronic wounds? Drug and Therapeutics Bulletin 45, 57-61 (2007).] [Iqwig. Negative Pressure Wound Therapy. 2006. Ref Type: Internet Communication] As the evidence for VAC therapy is accumulating continuously also the evaluation of the available evidence should also be repeated regularly. A recent review summarizing not only the clinical evidence for efficacy of V.A.C. therapy but also providing a comprehensive description of how V.A.C. therapy is thought to improve wound healing was published by Hunter et al.

The value of the increasingly popular treatment for treating adults with chronic wounds has been questioned by Drug and Therapeutics Bulletin (DTB) in August 2007.

After reviewing the available evidence, DTB concludes that the "clinical effectiveness of this therapy is unclear, there have been substantial limitations associated with many of the studies assessing topical negative pressure, which cast doubt on the validity and reliability of the results."

Among the other conclusions are the following:

-- "In people with diabetes mellitus and post-amputation foot wounds (i.e. where a chronic wound has been converted into an acute wound by surgery), there is evidence from one study that vacuum therapy may lead to more rapid healing."

-- "There is no compelling evidence that topical negative pressure helps skin graft 'take', or the healing of pressure ulcers or simple diabetic foot ulcers."

-- "The treatment may accelerate healing in people with chronic venous ulcers who are treated with bed rest and punch grafts. In reality, however, few of those with this condition are likely to be offered hospitalization and bed rest due to the costs."

Lawsuit

KCI sued Blue Sky in federal court for patent infringement soon after Blue Sky's product won FDA approval.

On 3 August 2006 a Texas jury found that BlueSky Medical Group had not infringed upon any previous patents by way of what the system purports to do and how that differs from the KCI system. Blue Sky, for example, does not improve wound healing but has been approved to relieve intrabdominal fluid in patients for whom abdominal closure is unsafe. The courts confirmed that KCI did not have a patent on Negative Pressure Wound Therapy. Blue Sky's technology utilizes Antimicrobial(AMD) gauze or permeated with polyhexamethylene biguanide or PHMB. The AMD gauze provided in every application, works to reduce the bacterial load in the wound bed. The use of several different types of drains (round, channel and flat) with the use of AMD gauze is what separates the two different products. Both products use vacuums to bring accelerated granulation and closure to wounds, they just use different methods to get to that end. The difference is significant and the 40% dip seen in KCI stock the day after the judgment has largely been made up.Fact|date=April 2007

BlueSky Medical was purchased by Smith & Nephew plc in May 2007. The Advanced Wound Management division of Smith & Nephew plc (LSE: SN, NYSE: SNN), the global medical technology business, moved the operations of its negative pressure wound therapy (NPWT) business from California to its US headquarters in Largo, Florida.

ee also

VAC Therapy

External links

* [http://www.boehringerwound.com Engenex NPWT System with Bio-Dome Technology]
* [http://www.o-wm.com/article/3815 Ostomy Wound Management article “Negative Pressure Wound Therapy: A Rose by Any Other Name – Michael S. Miller, DO, FACOS, CWS; Chris A. Lowey, MA, DO.]
* [http://www.kci-medical.com KCI]
* [http://www.blueskymedical.com Blue Sky]
* [http://www.medelasuction.com/USA/en/suction/systems/Invia.php Medela Invia Healing System]
* [http://www.npwt.com Negative Pressure Wound Therapy]

* Topical negative pressure for chronic wounds? Drug Ther Bull 2007; 45: August 2007 http://press.psprings.co.uk/dtb/august/57_dtaugust.pdf

References


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