Negative Pressure Helps Some Diabetic Ulcers


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 other 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 explained.

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

Although the exact mechanism of action has not been identified, negative-pressure therapy reduces edema, uniformly draws wound edges together, and may promote both cytokine elaboration and angiogenesis.

The therapy can be performed on an outpatient basis, although the set-up is bulky, Dr. Armstrong noted.

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 when treated 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) receiving continuous treatment with the vacuum-assisted closure (VAC) system for the 112-day study period. Just 33 of 85 patients receiving standard moist wound care healed completely.

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

There was a trend toward fewer reamputations in patients who received VAC, although the study was not powered to evaluate that end point.

Even though the study was met with some criticism for allowing clinical judgment to guide therapeutic interventions, Dr. Armstrong said that such a study design is necessary for research 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 manufactured 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. Referring to the oft-quoted phrase, “Don't just do something, stand there,” Dr. Armstrong noted that physicians are sometimes reluctant to follow that advice.

“You feel like squirting something, spraying something, applying something to the wound. Much of this really helps people, but some of it won't,” Dr. Armstrong commented.

Well-designed trials with appropriately selected patients will point the way to “keeping a few more limbs on a few more bodies,” he added.