Temple University School of Podiatric Medicine Journal Review Club
Editor's note: This post is part of the Temple University School of Podiatric Medicine (TUSPM) journal review club blog series. In each blog post, a TUSPM student will review a journal article relevant to wound management and related topics and provide their evaluation of the clinical research therein.

Article Title: Negative-Pressure Wound Therapy for Management
of Diabetic Foot Wounds: A Review of the Mechanism
 of Action, Clinical Applications, and Recent Developments
Author: Muhammed Y. Hasan, MBBS, MRCS (Ed), Rachel Teo, MS, and Aziz Nather, FRCS (Ed)
Journal name and Issue: Diabetic Foot & Ankle, Vol. 6, Issue 1 (2015)
Reviewed by: Deep N. Shah, Class of 2019, Temple University School of Podiatric Medicine

Introduction

Negative-pressure wound therapy (NPWT) plays an important role in the treatment of trauma wounds, general surgical wounds, and diabetic foot wounds.

Mechanism of Action

Morykwas’ work on animal models described the role of NPWT role as a facilitator in creating an “ideal” wound- healing environment. In addition, NPWT is thought to improve dermal blood flow through vasomotor mediators for negative pressures of up to 125mmHg. NPWT induces direct macrodeformation leading to wound contraction and size reduction. Moreover, NPWT produces granulation compared with conventional dressings and induces angiogenesis and vascular proliferation. Furthermore, NPWT mobilizes the systemic endothelial progenitor cells that are markers of healing and repair. NPWT removes excess wound fluid that not only reduces edema but also enhances local blood and nutrient flow. This therapy also provides a safety barrier that shields the wound from environmental contaminants as a result of more rapid reduction in bacterial colonization.

Clinical Application

NPWT is used for post-debridement wounds following surgery for necrotizing fasciitis, foot abscesses, infective heel ulcers, and exposed bone, capsule, and tendon. Selection criteria:

• Wound ischemia: Wounds selected must have at least one palpable foot pulse and a good capillary filling time (<2 sec).
• Sensory neuropathy: Because neuropathy is an important predictor of ulcer recurrence, patients must be assessed appropriately before NPWT, such as with Semmes Weinstein monofilament testing and neurothesiometer testing.
• Presence of deep infection: Osteomyelitis and septic arthritis are contraindications to NPWT because application of the device over an underlying infection can essentially enclose the infection and create an abscess

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Before Application of Negative-Pressure Wound Therapy

Adequate and proper debridement must be performed to remove all devitalized, necrotic, and infected tissue. Proper monitoring of glycosylated hemoglobin control is performed, along with monitoring of other healing markers such as hemoglobin, albumin, pre-albumin, lymphocyte, and creatinine levels. In addition, antibiotics sensitive to the organism cultured are administered to help clear the infection and achieve a reduction in bacterial load.

Pressure Setting

The NPWT pump delivers the desired negative pressure to the entire system. In vitro studies showed that at subatmospheric pressures of 125 mm Hg, there is a fourfold increase in blood flow. In clinical practice, 125 mm Hg is the normal setting, although levels can vary between 50 and 150 mm Hg depending on the wound type. Higher pressures can be used when high exudate and wound fluids are present. Pressure modes can be changed among continuous, intermittent, and variable delivery.

Conclusion

Overall, in diabetic wound management, NPWT is still an evolving technology, with systems such as vacuum-assisted closure , Vivano™ (Paul Hartmann AG, Heidenheim, Germany), and Renasys-GO™ (Smith & Nephew,, London, United Kingdom). Because most of these wounds manifest with infection, the success of NPWT in this cohort is still highly dependent on the adequacy of surgical debridement and antimicrobial coverage, given that the foregoing technologies showed no difference in clinical efficacy among the three systems when treating both acute and chronic wounds.

Evolving NPWT technology including instillation therapy, nanocrystalline adjuncts, and portable systems can further improve results if used with correct indications. In diabetic foot management, NPWT has had a significant impact on limb salvage. However, it is important to emphasize that diabetic foot management is a multidisciplinary effort, and NPWT is only one of the essential tools in overall management. Successful outcome is heavily dependent on all treatment modalities, including adequate wound debridement, appropriate antibiotic therapy, optimization of healing markers, and meticulous wound monitoring.

About the Author
Deep N. Shah is a third-year podiatric medical student at Temple University School of Podiatric Medicine (TUSPM) in Philadelphia, Pennsylvania. He graduated from Siena College in Albany, NY in 2015 with a Bachelor of Science in Biology with minor in Business Administrations. Deep holds a keen interest in diabetic limb salvage, wound care, and reconstructive surgery and hopes to use his platform as a future podiatrist to educate and enlighten surrounding communities on the importance of foot care.

Dr. James McGuire is the director of the Leonard S. Abrams Center for Advanced Wound Healing and an associate professor of the Department of Podiatric Medicine and Orthopedics at the Temple University School of Podiatric Medicine in Philadelphia.