Negative pressure wound therapy (NPWT)

Negative pressure wound therapy (NPWT) is an approach to wound treatment in which a vacuum dressing is applied to an open wound to promote healing. NPWT is most commonly used in the treatment of various acute and chronic wounds, as well as burn wounds. The treatment procedure requires the application of a sealed wound dressing connected to a vacuum pump that creates a negative pressure environment around the wound. Maintaining a negative pressure environment in this manner increases blood flow to and draws excess fluid from the wound site. NPWT can be applied continuously or intermittently for days or even months as needed. When administered properly, NPWT also offers a number of additional advantages over traditional wound dressing techniques beyond those related to blood flow and fluid removal. Some of these advantages include faster healing times, reduced infection risk, and fewer required dressing changes. Since the technique was first introduced in the 1990s, NPWT has enjoyed widespread use as an approach to wound management.

Background

Open wounds, which involve a break in the skin or other body tissue, are among the most common medical problems. Most open wounds are the result of injury, but some arise from non-traumatic causes as well. The main types of open wounds include abrasions, lacerations, punctures, and avulsions. Abrasions are scrapes. Lacerations are cuts. Punctures are wounds caused by pointy objects such as nails. Avulsions are a complete or partial tearing away of the skin and other tissue. Most such open wounds can be treated easily through cleaning, dressing, and the application of direct pressure and elevation. These methods serve to control bleeding, reduce the likelihood of infection, and encourage rapid recovery. Not all open wounds can be treated this easily, however.

Certain types of open wounds may require more careful treatment. Open wounds that do not heal normally often need to be treated using more advanced techniques that go further than simple cleaning and dressing. Diabetic ulcers are one type of open wound that often fail to heal normally. Diabetic ulcers typically heal poorly because diabetes causes small blood vessels in the extremities to grow narrower over time. This reduces blood flow and makes it harder for wounds to heal. Pressure ulcers, or bedsores, are another type of open wound that often heal poorly. Pressure ulcers arise when continuous pressure applied on part of the body eventually leads to reduced circulation. When circulation is interrupted in this manner, the accompanying lack of oxygen and nutrients can damage cells and tissues and ultimately result in the formation of a lesion. If left untreated, such a lesion can develop into a dangerous open wound that is difficult to treat. Other potentially poor healing open wounds include ulcers found in veins and arteries, first- and second-degree burns, wounds with an excessive amount of drainage, and wounds that are at especially high risk of infection. Treating open wounds such as these is a challenging prospect because they present conditions that are simply not conducive to the body's natural ability to heal itself. NPWT offers a means of treating difficult wounds in a more effective manner that addresses many of the special concerns that these wounds present.

Overview

NPWT is a relatively simple procedure that can have great benefits. To begin the process, a physician cleans and prepares the wound for dressing. Once the wound is ready, the physician cuts a piece of sterile open-cell foam and packs it into the wound. This foam serves as a filter that prevents blood clots, loose tissue, and other particles from clogging the vacuum system during treatment. With the foam packing in place, the physician places a special polyurethane dressing over the wound. This thin dressing creates an impermeable, airtight seal around the wound. The physician then attaches a vacuum pump to the dressing. When the pump is activated, it creates a subatmospheric vacuum environment that promotes healing.

The vacuum pump used in NPWT can be adjusted so that it operates based on the patient's needs. Specifically, the pump can be set to provide suction continuously or in intermittent cycles. Continuous suction is usually prescribed when the patient's wound is draining excessively. When a patient undergoes NPWT, treatment almost always begins with continuous suction because open wounds typically exhibit the heaviest discharge at the beginning of the healing process. During intermittent suction, the vacuum pump is programmed to cycle at a rate that is consistent with the rate at which the wound is draining. This approach keeps the wound's moisture content optimized at all times.

As with any other method of treating an open wound, patients undergoing NPWT must have their dressings regularly changed. In most cases, dressings are changed every three to seven days or as conditions require. Although dressing changes are generally pain free, patients are often administered painkillers prior to a change so as to minimize discomfort.

NPWT promotes healing in a number of important ways. First and foremost, it removes any barriers to cell proliferation and migration. This, in turn, helps to expedite the formation of new connective tissue and microscopic blood vessels necessary to complete the healing process. NPWT also provides a protected wound care bed and removes any potentially infectious materials. In addition, NPWT helps to increase blood flow to the wound site and provides a means for the removal of excess discharge. If excess discharge is not properly removed, tissues in and around the wound site can begin to soften and break down due to excess moisture. Finally, NPWT also helps to reduce swelling.

The effectiveness of NPWT is dependent on routine monitoring. To get the best possible results, physicians and nurses must ensure that the negative pressure seal remains unbroken and that leaks are kept to a minimum. They must also ensure that there are no kinks in the tubing that runs between the pump and the dressing. Other monitoring tasks include making sure the drainage chamber is working properly and emptying it when necessary, changing the dressing as required, and observing any changes to the area around the wound.

There are some instances in which NPWT should not be performed. This includes when a wound presents with fistulas to organs and body cavities, when necrotic tissue or scabbing has not been properly removed, and when surrounding bone is infected with osteomyelitis. NPWT should also be avoided in the case of wounds caused by skin cancer.

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