Negative Pressure Wound Therapy and Ultraviolet Light: A Novel, New Adjunct?

Ancient Egyptians and Romans believed that sucking on a wound with one’s mouth could remove poisons and evil humors from within. By the late 1990s, this concept evolved into negative pressure wound therapy (NPWT) as doctors advanced in the study of microbes and left humoral theory behind.

Throughout the 20^th century, doctors experimented with the tissue and wound response when under suction of a glass cup and various vacuum sealing systems. Then in 1997, Louis C. Argenta and Michael Morykwas published an article with results that intermittent pressure provided optimal blood flow patterns at 5 minutes on and 2 minutes off.

The use of NPWT is now considered an “essential therapeutic advancement for the temporization of definitive soft-tissue coverage,” according to the authors of a recent review of reconstruction surgeons’ armamentarium and approach published in Burns & Trauma. The wound care adjunct is thought to aid in wound healing in that it increases blood flow while preventing edema, inflammation and tissue fibrosis that complicate microvascular reconstruction.

While NWPT has not been proven as effective as debridement at reducing the bioburden in a wound, a recent study explored how the adjunct therapy could become more effective in inhibiting bacterial proliferation.

NPWT and Ultraviolet-A: A New Approach for Wound Care Treatment?

Infected diabetic foot ulcers (DFU) are one of the most common causes of hospitalization and amputation among diabetic patients. Infections have also been found to be directly associated with delayed wound healing in chronic wounds.

Inspired by the poor outcomes and severity of diabetic foot ulcers, researchers at the University of Texas set out to study whether the use of NPWT in conjunction with Ultraviolet-A (UV-A) therapy could inhibit bacterial proliferation in chronic, non-healing wounds.

In the study, recently published in the Journal of the American Podiatric Medical Association, five pigs with full thickness excisional wounds were treated with either -125 mmHg NPWT (NPWT), -125 mmHg NPWT + UV-A fiber optic therapy (NPWT + UV-A) or saline-moistened gauze (control).

Among the findings:

• • The size and number of bacteria colonies examined in vitro decreased. After 24 hours, the NPWT + UV-A therapy resulted in significantly smaller colonies of both Staphylococcus aureus and Pseudomonas aeruginosa than the control. The colony number of both strains also decreased when UV-A was combined with NPWT.

• • Reduced wound area. After 14 days of treatment, the wounds that were treated with NPWT + UV-A were found to have a significantly reduced wound area compared to both NPWT alone and the control.

While an animal model was used for this study, these results could potentially have applications for post-operative wound debridement or amputation patients. Davis et al. believes the addition of UV-A to NPWT could help reduce the wound bioburden by treating residual infection or bacterial colonization. They also note that UV-A could be utilized outside of the immediate perioperative period in patients who are undergoing extended negative pressure wound therapy courses for larger wounds.

The Challenge of Bioburden and Biofilm in Chronic Wounds

Beyond bioburden, the biofilm phenotypic state is considered to be more fundamental in preventing chronic wounds from healing in a timely manner. While several studies have examined the role of biofilms in chronic non-healing wounds using animal data, Malone et al., 2017 sought to quantify the presence of biofilms in human chronic wounds. Their meta-analysis of 554 studies from the literature databases revealed the prevalence of biofilms in chronic wounds to be especially prominent at 78.2%.

Biofilms are thought to be so detrimental to chronic wound healing that the U.S. Department of Defense has made biofilm and chronic wound research a priority in recent years. For example, current research is aimed at understanding the formation of and developing treatment strategies for plaque, which researchers hope will help them to treat and prevent biofilms of bacterial species found in combat wounds.

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