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.
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.
Periwound problems are perhaps the most challenging issues to manage with NPWT. Using registry data from the Intellicure National Wound Registry, periwound issues were among the most common reasons for interruption of NPWT, including maceration and candida. Interruption of therapy often occurred for 7 days allowing the skin time to recover. To protect the periwound skin, use of a skin barrier wipe for protection with each dressing change goes a long way towards prevention, and it is common to use products such as hydrocolloid dressings around the wound attaching the majority of the drape to the hydrocolloid. Additionally, if the interface dressing will possibly lie on intact skin, or needs to be bridged to an adjacent area, it is imperative that adhesive film/drape be applied first to protect the skin. This can be accomplished by either cutting strips to “picture frame” the wound or one large piece can be applied over the wound and forceps and iris scissors used to trim away the drape right at the skin/wound junction for easy and perfect coverage.
The average outpatient seen at a wound center has approximately 2 wounds. Thus, it is common to consider using one NPWT device on more than one wound, if proximity allows. Not all devices on the market allow this, and even if the device makes this technically feasible, it may not be practically possible. Caroline once had a patient with bilateral foot wounds who continued to ambulate. Although they joked about it at the time, connecting both feet together via Y-connected tubing in an ambulatory patient was not a viable option. Multiple wounds on one foot can usually be easily bridged together. This example is shown using foam; the various manufacturers with other types of interface dressings can provide tips for accomplishing this.
Debate often centers on how to manage exposed deep structures such as bone or tendon. Official recommendations from manufacturers caution against attempting to granulate directly over either, but we all have our favorite story of success doing just that, and at times this may be the only option short of amputation. Allowing a tendon to granulate may make skin grafting possible, even if there is a partial sacrifice of mobility. The greatest success, particularly with tendon that glides as the patient is ambulating, is immobilization of the extremity with an orthotic device that continues to allow ambulation while keeping the tendon stable and unmoving.
Vascular structures, organs and viscera must be handled with great care and must be protected from direct exposure to negative pressure. The decision to use NPWT in many cases is the best one to facilitate more rapid granulation tissue into a wound space. It is critical that this is a team decision including the surgeon, and any wound care providers involved in the care. Knowledge of the surgery performed, the anatomical location, potential vulnerable structures/vessels/organs in the vicinity of the wound must be taken into consideration. Local granulation tissue recently developed may not be adequate protection, so a protective interface layer should always be used until the surgeon/wound provider feels it can be eliminated.
Adherence to the wound bed and “lost foam:” According to the FDA, retention of foam dressing pieces and foam adhering to tissues or imbedded in the wound were noted in 32 injury reports. The majority of these patients required surgical procedures for removal of the retained pieces, wound debridement, and treatment of wound dehiscence, as well as additional hospitalization and antibiotic therapy. Given the total number of NPWT treated patients over the years, this represents a tiny fraction of patients. However, most of us have seen adherence of sponge or remnants of gauze on the wound bed at one time or another. Careful inspection of the wound bed at dressing changes to identify small pieces of foam or gauze threads enables easy removal with forceps at the time of the dressing change.
From a safety and practical standpoint, a singular piece of dressing material should be used whenever possible when packing a wound for NPWT. There will always be times that this is not possible, at which time it is imperative to document in the medical record how many pieces were utilized, and for further safety even marked on the top of the actual dressing film. When small pieces are packed into deep wound pockets, movement of tissue planes can actually cause dressing materials to migrate deeper into the wound spaces and be missed if the clinician removing the dressing is not the same one who applied it.
In 2009, the FDA posted alerts on its website concerning reports of 6 deaths and 17 injuries associated with bleeding from NPWT systems. Bleeding occurred in patients with vascular grafts (such as femoral and femoral-popliteal grafts), in sternal and groin wounds, in patients receiving anti-coagulant therapy, immediate post-operative wounds and during removal of dressings that adhered to or were imbedded in the tissues. Three years earlier, registry data was accessed from the Intellicure Research Consortium to evaluate the frequency of adverse events with NPWT. The records of 9,119 patients with 20,371 wounds treated from August 2001 to November 2006 were evaluated. NPWT was provided to 931 patients (10% of total patients) and 9.6% of these NPWT patients were on either heparin or coumadin. None of the NPWT patients reported bleeding. A further 29.5% of NPWT patients were on other rheological agents such as plavix or pletal. In one case, the NPWT device was discontinued due to bloody drainage in an exceptionally large wound (initial leg ulcer was 342 cm2, being in the 99th percentile of wound size for all wounds treated at all wound centers). Excessive bleeding with NPWT still remains uncommon, but clinicians must remain vigilant in its application.
There is conflicting data regarding whether NPWT increases or decreases the bacterial burden of the wound bed. NPWT is used more and more often in acute serious processes such as necrotizing infections. Silver containing foam has been shown in animal studies to decrease bacterial colonies, and the gauze product used primarily with NPWT devices is antimicrobial; containing polyhexamethylene biguanide (PHMB), and some devices allow antimicrobial preparations to be instilled. Nevertheless, most clinicians are familiar with the distinctive unpleasant odor common to the use of foam dressings. This odor does not indicate that the wound is infected but can be a clinical frustration and a social issue for patients. Clinical guidelines recommend that if NPWT is used in the presence of acute infection, the infection must be being treated, and consideration should be given to changing the dressing more frequently based on the patient’s condition until the infection is under control.
The opportunities for misapplication of negative pressure are numerous. Early in Caroline’s use of NPWT, the mother of her hospital CEO was hospitalized with a surgical dehiscence. An inexperienced nurse applied NPWT foam over her intact skin. The result was an excellent example of the capability of NPWT to develop granulation tissue through intact skin. In the acute or LTC setting there often are designated staff (either nursing or physical therapy) that may do the majority of NPWT dressing changes. But all staff, particularly nursing, should have regular inservicing and competency updates to troubleshoot alarms, repair leaks and observe for complications.
Misuse by patients:
Complications may also occur if patients do not properly follow instructions. The importance of continuous suction with no more than 2 hours of the device being turned off is a critical teaching point with patients. Devices may be noisy and interrupt sleep; patients decide to remove the suction while they go to work or out for an evening event. We have seen cases of extreme maceration because patients turned off their NPWT machines thus trapping wound fluid in the wound bed for many hours. Some of the different devices have monitors to allow the clinician to monitor the number of hours NPWT has been used since the patient was last seen, and if it is noted that the patient is not utilizing the suction for the prescribed number of hours, a frank discussion needs to occur with the patient not only about the potential negative effects, but also the lack of therapeutic benefit from poor utilization of the therapy. For patients who have been on long-term therapy, they may just be weary of being constantly connected to the device. Allowing the patient to take a “break” from therapy for a week, what they call in Dot’s clinic a “VAC”-ation can go a long way towards resumption of continuous use, and a happier patient who feels like they still have some control over their situation.
Critical Teaching Points:
Patient education all along the healing pathway must be made a priority. The various devices should have patient education material available for home use as a reference as questions may arise, as well as phone numbers available for patients to call for technical questions and assistance. Patients must be taught, and provide return demonstration for plugging in and charging the device, how to turn on and off, and how to change the canisters. Patients or their family/caregivers need to understand what normal exudate is and what is not normal. They must be able to remove the dressing and have an alternative dressing available at home. They must know to call the clinic or go to the emergency room for extremes in pain or drainage. And, most importantly, what to do if frank bleeding should occur.
Most likely many patients will be followed by home care nurses for dressing changes at home, with the exception of those that don’t qualify for home care or prefer the dressing changes be done at the clinic. The choice of home care agency is often driven by insurance, but when choices are available, having a few agencies that have nurses well trained in NPWT that can speak the language and understand specific suggestions and orders is ideal. Unless potential harm exists, clinicians in the wound center should try to refrain from being overly critical of dressings done in the home setting so as not to undermine patient confidence. Patients will often compare the dressings done in the two settings, but we must keep in mind that we have elevating chairs/stretchers, the best lighting, and often extra hands if needed. The home setting often is the total opposite.
NPWT has become a vital part of our clinical options for treating wounds of all types. No longer reserved for the large wounds only, most utilize it as a short therapy to improve a wound bed or decrease the time to healing for smaller wounds and to improve graft/flap take. When used as a component of a comprehensive wound treatment program, most wound centers cannot imagine practicing without it.
Dr. Caroline Fife, is currently Co-editor of Today’s Wound Clinic, is the Director of Clinical Research at the Memorial Hermann Center for Wound Healing, Houston, Tex., and Chief Medical Officer of Intellicure, Inc. She can be reached at firstname.lastname@example.org
Dot Weir, RN, CWON, CWS is the Wound Care Director for Osceola Regional Medical Center in Kissimmee, Fla. and is co-editor of Today’s Wound Clinic.