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.

History
Negative Pressure Wound Therapy in its present form 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 1997, 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 recognition of this origin is challenged by some in the medical industry, who cite Russian studies (The Kremlin Papers) done in 1986 and 1987, in which a vacuum was used to clean wound beds, and an intermittent vacuum therapy was applied with a chamber device to the wound. These studies are subject to interpretation, and whether or not they describe Negative Pressure Wound Therapy is unclear.

Current use
Currently there are two primary suppliers of NPWT systems in the medical industry. Kinetic Concepts (KCI) uses the patented V.A.C. (vacuum assisted closure) system described by Morykwas and Argenta, and Blue Sky utilizes the Chariker-Jeter system, which the company says is derived from “The Kremlin Papers”. KCI sued Blue Sky in federal court for patent infringement soon after Blue Sky's product won FDA approval.

On August 3rd, 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. However, Blue Sky's technology does not have the ability to completely remove edema as it utilizes gauze. Gauze is hydrophilic material that retains moisture. The difference is significant and the 40% dip seen in KCI stock the day after the judgement has largely been made up.

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, plans to move the operations of its negative pressure wound therapy (NPWT) business from California to its US headquarters in Largo, Florida.

Effectiveness
The value of the increasingly popular treatment has been questioned by Drug and Therapeutics Bulletin (DTB). "Doubt cast over clinical effectiveness of popular wound therapy," Drug and Therapeutics Bulletin, August 2007.

After reviewing the available evidence, DTB concludes that the "clinical effectiveness of this therapy is unclear."

Among the other conclusions are the following:

-- "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."

-- "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 hospitalisation and bed rest due to the costs."