By Laurie Swezey RN, BSN, CWOCN, CWS, FACCWS

Tunneling wounds can be difficult to heal and often take several weeks to months to close. The following will discuss tunneling wounds and how negative pressure wound therapy can be used to heal them.

What is a Tunneling Wound?

A tunneling wound is any wound that has a channel that "tunnels" from the wound into/through the muscle or subcutaneous tissue. Some wounds may have more than one tunnel. Tunnels may be short and shallow or long and deep. They sometimes hide from view and may only be discovered when the wound is probed (which is the main reason we probe wounds).

Causes of Wound Tunneling
Tunneling of a wound may occur for various reasons:

• infection- results in destruction of tissue
• too little/too much packing- using too much packing can degrade newly granulated tissue, while using too little packing may not absorb drainage adequately and may increase the risk of abscess formation
• pressure- pressure and shear forces may be concentrated where the tissue layers meet, resulting in tunnel creation
• chronic wounds- prolonged inflammation may lead to tunneling

Measures to Optimize Tunnel Closure
In order to promote healing, the wound must be kept clean. Soft-tipped irrigation cannulas can be used to gently cleanse the tunnels and the wound itself. If infection is suspected to be the reason for tunneling, appropriate antimicrobial therapy should be instituted. Any dead (necrotic) tissue should be debrided. Nutrition should be optimized. Clients with diabetes should be counseled and assisted to bring their blood glucose levels as close to normal as possible. The wound should be packed according to best practice guidelines (see above regarding packing). The tunnel(s) should be probed and measured at least weekly, and dressing selection should be chosen based on the wound size, drainage, and location.

Sometimes, despite our best efforts, tunnels fail to close and wounds stall in the healing process. When this happens, negative pressure wound therapy may "jump start" the healing process.

Negative Pressure Wound Therapy Indications

According to the Agency for Healthcare Research and Quality (AHRQ), negative pressure wound therapy (NPWT) is indicated for:

• wound retraction
• stimulation of granulation tissue formation
• continuous wound cleansing
• continuous removal of exudates
• reduction of interstitial edema

Foam (sometimes containing antibiotics, such as silver) or moistened gauze are the most commonly used wound dressings in NPWT and are used to fill the wound. Both dressings require a transparent adhesive film dressing to seal the wound. After the dressing has been applied, an evacuation tube runs from the wound through the dressing, collecting the wound exudate into a container attached at the other end. A vacuum pump is used to provide intermittent or continuous suction, depending on the wound characteristics and physician orders.

Negative Pressure Wound Therapy and Tunneling
Tunneling is not a contraindication for NPWT; in fact, this therapy has been used successfully on wounds with extensive tunneling. The wound, including any tunnels, should be dressed/packed according to best practice (not too tightly or loosely). Foam may be used, but should be avoided in very narrow tunnels. Some manufacturers of NPWT equipment also manufacture their own dressing/packing supplies. Foam should be in contact with the wound bed only just to the surrounding edges — avoid packing too tightly and placing friction on these edges. Dressing may need changing every 48 hours for the first several days; when drainage decreases, this time may be extended to 72 hours. With every dressing change the wound should be evaluated for effectiveness of the therapy. If the wound has not decreased by 10% after the first week or by 50% in week four (or has gotten worse) discontinuation of NPWT should be considered.

Sources
Aguinaga, S. (2007). "Positive steps towards negative pressure wound therapy". MedSurg Nursing. FindArticles.com. May 18, 2012.
Agency for Healthcare Research and Quality. Technology assessments: negative pressure wound therapy devices. http://www.ahrq.gov/clinic/ta/negpresswtd/npwtd02.htm

Image Credit: Medetec (www.medetec.co.uk).

About The Author
Laurie Swezey RN, BSN, CWOCN, CWS, FACCWS is a Certified Wound Therapist and enterostomal therapist, founder and president of WoundEducators, and advocate of incorporating digital and computer technology into the field of wound care.

The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, Kestrel Health Information, Inc., its affiliates, or subsidiary companies.