Cath Lab Digest

The Challenges of Negative Pressure Wound Therapy in Clinical Practice

This article is a joint effort by Dot and Caroline, bringing together perspectives from our combined (too many to confess) years of practice. We have brought our slightly different but complementary viewpoints together on the clinical challenges of Negative Pressure Wound Therapy (NPWT).

Caroline remembers the first patient on whom she used negative pressure wound therapy. It was 1997, only two years after FDA clearance of the first device. The patient was a young, obese woman who had a surgical dehiscence of her abdomen extending from the xyphoid to the pubic symphysis which undermined along both side walls more than the width of her hands. It was the biggest open wound she had ever seen in an ambulatory outpatient. She had been sent home to perform her own saline wet to dry dressings, which she had been doing for weeks. A KCI representative came to Caroline’s office to tell her about “The VAC” and her response was, “You have a machine that sucks on wounds? Why would anyone want to do that?” But she decided this would be the first patient on which to try this odd idea, and within about 16 weeks her enormous abdominal wound was completely closed. She was even very proud of the poor quality Polaroid photos taken of her first use of NPWT. Despite her excellent response however, she did have one complication. Marlex mesh which had been placed to control an abdominal hernia became infected. After the wound closed she developed a small abscess which had to be surgically explored. That was not the “fault” of negative pressure, but was the first of many lessons Caroline learned about the use of it.
Thirteen years (and hundreds of patients) later, we have seen every possible success from negative pressure, and probably every possible complication. Negative pressure is used for reasons other than wound healing, such as in the management of abdominal compartment syndrome and support and bolstering of flaps and grafts. In this article, we will discuss only the challenges associated with the use of negative pressure for wound healing.
The first thing to be observed is that negative pressure wound therapy is incredibly safe. Since FDA clearance of the original device in 1995, there have been millions of patient days of therapy with only a handful of significant complications. However, every clinician is aware of the various “challenges” associated with the use of negative pressure. Technique is critical, particularly in its application. Many clinicians are true “artists” when it comes to NPWT application. Then there is the clinical judgment element. How much suction should I use and when should I increase it or decrease it? Should I use intermittent or continuous suction? How do I determine when has the patient has had optimal response? Do we stop when granulation is established or when the process is complete? Do we stop this week or next month?
We have only our clinical experience to guide us for most of these decisions. And now that there are many NPWT devices from which to chose we find that we have even MORE questions than before. Which interface should be used? What is the optimal range of pressure? Without attempting to comment on one device versus another, we thought we would outline some of these clinical issues.

The components:
Regardless of the device selected, the use of negative pressure requires 4 essential elements: 1) there must be an air tight seal with the dressing, and this necessitates the use of an adhesive drape, 2) there must be some sort of interface with the wound, 3) there must be a source of negative pressure or “suction” (usually a mechanical device) and 4) there must be a connection to the device (usually some sort of connector and tubing). Challenges can arise with each of these elements.

Location, location, Location:
Some of the greatest challenges to NPWT occur due to the location of the wound on the body. Peristomal wounds, genitalia wounds, facial wounds, and wounds on weight bearing surfaces require careful consideration with regard to the placement of the connection to the device and the tubing. Ulcerations from poor placement of tubing can occur by allowing patients to lie or walk on NPWT components. Foam has been most commonly used to allow the suction to be easily moved away from a difficult area to a more convenient area for device placement (commonly called “bridging”). Dressing kits specific to this technique are now available, and as usage of other interface dressings has increased, similar “tricks of the trade” have emerged. Experienced clinicians have many methods to manage wounds in awkward locations, like using stoma paste or pectin rings/strips to border irregular areas and fill in spaces or gaps around abdominal, perineal or groin wounds.