Negative Pressure May Aid Healing of Foot Ulcers

BY BETSY BATES

SAN FRANCISCO -- Negative-pressure vacuum therapy appears to speed healing and increase the likelihood of complete closure of nonhealing diabetic foot ulcers, Dr. David G. Armstrong said at the annual meeting of the American Academy of Dermatology.

But negative pressure, like any therapy for nonhealing wounds, should be "married with good common sense" and the critical steps of debridement and pressure offloading.

"In my opinion, what this device does is make complicated wounds [simpler]. Once you get a nice carpet of granulation tissue, then stop," advised Dr. Armstrong, professor of surgery and chair of research at Rosalind Franklin University of Medicine and Science in North Chicago, Ill.

In negative-pressure wound therapy, subatmospheric pressure is delivered to the wound through a pump attached to a foam dressing. A canister collects exudate wicked from the wound.

Dr. Armstrong recommends that a stoma paste or hydrocolloid be placed around the periphery of the wound to prevent maceration from exudate collected during the process.

Although the exact mechanism of action is unknown, negative-pressure therapy reduces edema, uniformly draws wound edges together, and may promote cytokine elaboration and angiogenesis.

At a cost he likened to a moderately priced hotel stay--$70-$100 a day--the therapy is not cheap, but it could reduce the overall cost of healing diabetic foot ulcers if it keeps patients out of the hospital.

Diabetic foot ulcer treatment averages $28,000, and 75% of those costs are related to the hospital stay.

In a recently published randomized trial, Dr. Armstrong and Dr. Lawrence A. Lavery of Scott and White Memorial Hospital in Temple, Tex., found that large, deep diabetic foot wounds secondary to amputation healed faster and more completely with negative-pressure therapy than with standard wound care (Lancet 2005;366:1704-10).

Wounds closed completely in more than half of the patients (43 of 77) who received continuous treatment with the vacuum-assisted closure (VAC) system for the 112-day study period. Of the 85 patients who received standard moist wound care, only 33 healed completely.

"Rapid granulation tissue formation provided a clinical 'wow!' factor," in the VAC group, Dr. Armstrong said.

There was a trend to fewer reamputations in patients receiving VAC, although the study was not powered to demonstrate that end point.

Although the study received some criticism for allowing clinical judgment to guide therapeutic interventions, Dr. Armstrong said that such a design is necessary for studies to have "real world" relevance.

His study enrolled patients with wounds eight times larger than those in previous trials of negative-pressure therapy.

"It may be that in some trials, the less you need [interventions], the better they work," Dr. Armstrong said. The study used the VAC therapy system made by Kinetic Concepts Inc., which sponsored the research.

Dr. Armstrong stressed throughout his talk the need for matching wound therapies to the right patients and wounds. Not every nonhealing wound needs negative-pressure therapy, for example. Well-designed trials with appropriately selected patients will point the way to "keeping a few more limbs on a few more bodies," he said.

When asked to comment on this presentation, Dr. George Andros, chief of vascular services, Saint Joseph Medical Center, Burbank, Calif., stated: "The Lancet trial confirms what clinicians have known for years; negative-pressure vacuum therapy heals more diabetic foot ulcers and heals them more quickly than conventional therapy."