Negative Pressure Wound Therapy Achieved by Vacuum-Assisted Closure: Evaluating the Assumptions
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Index: Ostomy Wound Manage.2007;53(1):52-57.
Managing and treating complex wounds always have been difficult. The aging of the population and the survival of individuals with multiple comorbidities and more complex pathologies have increased wound care challenges. In 1997, Argenta and Morykwas1 published a prospective cohort study describing a new wound management method that involved the continuous and/or intermittent application of subatmospheric pressure to human wounds for extended periods of time. The authors identified 300 wound patients who presented with chronic wounds (eg, pressure ulcers, stasis ulcers), subacute wounds (wounds that had been open <7 days), and acute wounds (wounds that had been open <12 hours). All patients were treated with negative pressure until the wounds were completely healed, progressed to a point where they could be closed by a surgical procedure (skin graft or muscle flap), or the patient refused further treatment or died. Using these endpoints, 296 of 300 wounds had a positive response to negative pressure wound therapy (NPWT).
Negative pressure technology subsequently became known by several pseudonyms, including vacuum-assisted closure (VAC), topical negative pressure (TNP), vacuum sealing technique (VST), and sealed surface wound suction (SSS); it is informally referred to as the wound vac. While its novelty and origins are controversial,2 this technology has been patented and cleared for marketing by the US Food and Drug Administration (a regulatory mechanism that does not require submission of data from controlled efficacy trials). Currently, the wound vac is in widespread use throughout North America and Europe3; however, its relative effectiveness (enhanced ability to bring about wound closure as compared to other, more standard methods of wound therapies) and efficacy (singular capacity to bring about wound closure) remain in question. The utility of a new therapy also must be examined in terms of its cost effectiveness – ie, whether the technology produces similar or better outcomes at equal or lower costs – should be considered. The purpose of this paper is to describe the device, discuss the mechanisms by which it is thought to effect wound healing, and examine its relative efficacy. Information about the cost effectiveness of this technology remains to be published.
The device. Wound vac technology involves the use of a medical grade, reticulated polyurethane ether foam dressing that is attached to a non-collapsible evacuation tube which, in turn, is attached to a vacuum source. Side ports in the tube allow for communication between the tube and the reticulated foam dressing. The reticulated foam dressing is cut to closely conform to the geometry of the wound bed and is placed in the wound defect so the tube lies parallel to the skin. The reticulated foam dressing serves both to absorb wound exudate and to evenly distribute the negative pressure over the entire wound. An adhesive drape consisting of a transparent film is placed over the foam dressing and the tube, extending 3 to 5 cm beyond the edges of the wound, and is affixed to intact periwound skin, creating an airtight compartment over the wound bed. Distally, the evacuation tube is connected to a collection vessel that is connected to an adjustable vacuum pump. When the device is in operation, the pump creates a negative pressure that pulls effluent from the wound into a collection vessel. Typically, the vacuum pump can be programmed to provide various amounts of negative pressure on an intermittent or continuous basis depending on the wound type.