How Does NPWT Work?
Two NPWT devices are primarily used in the United States: the V.A.C.[R] (Vacuum Assisted Closure) Therapy[TM] system, offered by Kinetic Concepts, Inc. (KCI), and the Versatile 1[R] Wound Vacuum System by BlueSky Medical Group. Both use a closed system, meaning that neither the wound nor the components of the treatment are exposed to the air.
The V.A.C. system is applied to an open wound for periods of 48 hours. Suction is directed at the surface of the wound through an interface between the wound surface and either a black polyurethane or white polyvinyl alcohol foam that is cut to the appropriate shape of the wound and is then inserted to contact the entire wound. The less dense, more porous black foam is more commonly used on larger or deeper wounds; the white foam has better nonadherent properties that help protect skin grafts and promote graft survival. The foam allows for distribution of the negative pressure. Suction tubing is placed onto or in the foam, and then the entire wound/foam complex is covered with a clear plastic dressing to seal the wound. It is then connected to a suction pump for 48 hours at either constant or intermittent suction. Suction levels of -125 to -150 mmHg are usually applied. The drainage from the wound goes into a canister attached to the suction pump. Several variations in the size of the pumps and canisters allow for different levels of activity and different treatment locations.
With the Versatile 1 device, a single layer of gauze is placed over the wound, then a flat, silicone Hemovac drain is placed on the gauze over the maximum dimensions of the wound. A second piece of gauze is placed over the drain, creating a gauze “sandwich” around the drain as shown in figure 1. The gauze and drain are entirely covered with a clear, semipermeable dressing that is cut to fit the dimensions of the wound, with a small overlap onto the adjacent healthy skin creating a seal over the wound. The drain is connected to the tubing, which is then connected to the vacuum pump. The gauze is puffy before the vacuum pump is turned on. After the pump is turned on and suction is applied, the cotton gauze collapses and compresses the wound bed. Edema fluid is removed through the drain as shown in figure 2.
The use of negative pressure to promote healing of open wounds has considerable literature support for efficacy. The effects of NPWT are thought to promote wound healing through multipleactions, including the removal of exudate from the wounds to help establish fluid balance, (2) provision of a moist wound Environment, (3) removal of slough, (3) a potential decrease in wound bacterial burden, (4) a reduction in Edema and third-space fluids, (5) an increase in the blood flow to the wound, (3-7) an increase in growth factors, (8) and the promotion of white cells and fibroblasts within the wound. (9) Negative pressure brings tissue together, promoting caption, which allows the tissues to stick together through natural tissue adherence and increases healing.
There are multiple anecdotal reports and case reports of marked enhancement of wound healing with use of NPWT; however, there are relatively few controlled trials. Gray and Peirce recently conducted a review of the literature currently available on NPWT. (5) Results in the studies they reviewed suggest that NPWT may be superior to saline-moistened gauze in promoting healing of chronic wounds, and NPWT may be superior to topical antimicrobial agents and gauze in promoting healing of soft-tissue flaps and skin grafts. (5) Philbeck et al found that “healing time can be as high as 61% faster and 38% less costly with combination treatment utilizing a controlled-suction drain system.” (10)
Case Report 1
The patient is a 54-year-old man with a 20-year history of Multiple Sclerosis. He is wheelchair-bound–completely nonambulatory–and 6’2″ tall. Financial concerns precluded his having an appropriately sized and configured wheelchair, so he was forced to use a standard-size wheelchair with leg extensions. This resulted in his slumping in his chair and having great difficulty keeping his feet on the leg supports, which led to a progressive foot drop. These factors resulted in his developing stage 4 right ischial (buttock) Decubitus Ulcer and a stage 3 right malleolar (ankle) decubitus ulcer. On initial evaluation on October 15, 2003, the wounds appeared as shown in figure 3.
The Versatile 1 Wound Vacuum System was chosen for this patient because it can be used to provide active therapy at night while a patient is sleeping. This was an important consideration for a patient who has limited mobility. The wounds were treated with the Chariker-Jeter technique (2) by applying saline gauze in a single layer covering all aspects of the open wounds. A flat Jackson-Pratt drain was placed on the gauze, and each wound was covered with a clear, semipermeable dressing. The drains were then connected to the negative pressure device at a pressure of -80 mmHg for a period of 6 to 8 hours per day (usually at night while the patient slept). In the morning, after negative pressure therapy was ended, the patient’s wounds were redressed with moist saline gauze covered with a Tegaderm (3M) dressing for the remainder of the day. He would clamp the flat drain tubing before disconnecting the suction, thus allowing negative pressure to be maintained within the system without ongoing connection to the vacuum pump, and he would coil up the tube and tape it onto the wound dressing (nursing assistance might be required for this, for patients who cannot manage their own disconnection). Being unattached to the vacuum pump during the day allowed the patient greater ease in maneuvering his wheelchair.
After approximately two and a half months of NPWT, the patient’s ischial decubitus wound was healed (figure 4, A), and the lateral malleolar wound was rapidly healing. Less than two months later, the malleolar ulcer was completely healed (figure 4, B).
Case Report 2
The patient is a 66-year-old woman who suffered an incidental trauma to her right leg and developed a subcutaneous hematoma that subsequently became infected (figure 5). She underwent incision and drainage in addition to receiving parenteral antibiotics. She rated her pain at 10 out of 10. She could not tolerate compression therapy, and dressing changes caused significant discomfort. Negative pressure wound therapy with the V.A.C. device was initiated (figure 6). Black foam was cut to the appropriate configuration and inserted into the wound. Pressure of -125 mmHg on continuous suction was applied initially; at four weeks the pressure was increased to -150 mmHg.
The wound began to granulate rapidly. This was accompanied by a decrease in the patient’s pain. The V.A.C. was used for eight weeks, bringing the patient to complete wound closure (figure 7).
The effect of exposing wounds to subatmospheric pressure has been studied in a variety of settings for approximately 50 years. (1) Between 1970 and 1997, numerous articles appeared in the Russian literature, and in 1999, another was published in this country, exploring the use of negative pressure for managing suppurative (pus exuding) wounds. (8-13)
In 1985, Dr. Katherine Jeter explored a unique combination of products to deliver negative pressure to the wound bed. Together with Dr. Mark Chariker, she designed a clinical study in which they stated that “their closed suction wound drainage system revolutionized the management of enterocutaneous fistulae complicating ventral abdominal wounds.” (14)
In 1986, Kostiuchenok et al found that NPWT in combination with surgical debridement significantly reduced the bacterial burden within purulent wounds and resulted in improved wound healing. (4) Also in 1986, Davydov and colleagues found that vacuum therapy reduced the bacterial load and septic complications, reduced time to healing, normalized the immune process, reduced scar tissue formation, and reduced hospital stays. (9)
In 1997, Morykwas and Agenta (6,7,15) of Wake Forest University published three articles regarding their experience with a “new method for wound control and treatment….” (6) A system was described in which subatmospheric pressure was applied through a closed system to an open wound for periods of 48 hours. (6,7) The subatmospheric pressure was directed at the surface of the wound through an interface between the wound surface and a polyurethane sponge, allowing distribution of the negative pressure and use of either a constant or intermittent mode. The authors determined that “the application of controlled subatmospheric pressure creates an Environment that promotes wound healing. (6)
By 2003, NPWT was commonly accepted therapy despite the few randomized, controlled studies of its efficacy. An NPWT consensus group was formed that year in Canada. Their consensus paper contains a literature review, recommendations for specific chronic wounds, and survey results from the group based solely on the V.A.C. product. (16)
At the present date, the question is not whether negative pressure wound therapy is beneficial in wound healing, because numerous case studies and articles clearly document its efficacy. The questions that remain involve determining the optimum mechanism and protocols for deploying this therapy. In a recent review article, (17) we have called for further research to better define the parameters for pressure intensity, duration of treatment, interval between treatments, mode of application, and timing of application to provide the most efficient and cost-effective therapy. Although there is still much to learn to optimize NPWT, this therapy is currently improving outcomes for patients suffering with pressure ulcers and other difficult-to-heal wounds.
Michael S. Miller, DO, FACOS, CWS, is the Medical Director, Marta Ortegon is a Physician Assistant, and Cheryl McDaniel is a Staff Nurse at The Wound Healing Center, Terre Haute, Indiana. Thomas Serena, MD, FACS, CWS, is the Medical Director at Penn North Centers for Advanced Wound Care, Warren, Pennsylvania. For more information, phone Dr. Miller at (812) 234-4321 or fax (812) 478-9552. To send your comments to the authors and editors, please e-mail email@example.com. To order reprints in quantities of 100 or more, call (866) 377-6454.
1. Fleck CA, Frizzell LD. When negative is positive: A review of negative pressure wound therapy. Extended Care Product News 2004:92;20-5.
2. Zarogen A. Nutritional assessment and intervention in the person with a chronic wound. In: Krasner DL, Rodeheaver GT, Sibbald RG. Chronic Wound Care: A Clinical Source Book for Healthcare Professionals, Third Edition. Wayne, Pa.: Health Management Publications, Inc., 2001;117-26.
3. Barker DE, Kaufman HJ, Smith LA, et al. Vacuum pack technique of temporary abdominal closure: A7-year experience with 112 patients. The Journal of Trauma–Injury, Infection and Critical Care 2000;48:201-7.
4. Kostiuchenok II, Koller VA, Karlov VA, et al. [Vacuum treatment in the surgical management of suppurative wounds.] Vestn Khir 1986;137:18-21.
5. Gray M, Peirce B. is negative pressure wound therapy effective for the management of chronic wounds? J Wound Ostomy Continence Nurs 2004;31:101-5.
6. Morykwas MJ, Argenta LC, Shelton-Brown EI, Mc-Guirt W. Vacuum-assisted closure: A new method for wound control and treatment: Animal studies and basic foundation. Ann Plast Surg 1997;38:553-62.
7. Argenta LC, Morykwas MJ. Vacuum-assisted closure: A new method for wound control and treatment: Clinical experience. Ann Plast Surg 1997;38:563-77.
8. Davydov IuA, Larichev AB, Abramov Alu, Men’kov KG. [Concept of clinico-biological control of the wound process in the treatment of suppurative wounds using vacuum therapy.] Vestn Khir 1991;146:132-6.
9. Davydov luA, Malafeeva E, Smirnov AP, Flegontov VB. [Vacuum therapy in the treatment of purulent lactation mastitis.] Vestn Khir 1986;137:66-70.
10. Philbeck TE Jr., Whittington KT, Millsap MH, et al. The clinical and cost effectiveness of externally applied negative pressure wound therapy in the treatment of wounds in home healthcare Medicare patients. Ostomy Wound Manage 1999;45:41-50
11. Davydov luA, Larichev AB, Smirnov AP, Flegontov VB. [Vacuum therapy of soft tissues and suppurative wounds.] Vestn Khir 1988;141:43-6.
12. Davydov luA, Larichev AB, Men’kov KG. [Bacteriologic and cytologic evaluation of vacuum therapy of suppurative wounds.] Vestn Khir 1988;141:48-52.
13. Davydov luA, Larichev AB, Abramov Alu. [Substantiation of using forced early secondary suture in the treatment of suppurative wounds by the method of vacuum therapy.] Vestn Khir 1990;144:126-28.
14. Chariker ME, Jeter KF, Tintle TE, Bottsford JE. Effective management of incisional and cutaneous fistulae with closed suction wound drainage. Contemp Surg 1989;34:59-63.
15. Morykwas MJ, Argenta LC. Nonsurgical modalities to enhance healing and care of soft tissue wounds. J South Orthop Assoc 1997 Winter;6:279-88.
16. Sibbald RG, Mahoney J; V.A.C. Therapy Canadian Consensus Group. A consensus report on the use of vacuum-assisted closure in chronic, difficult-to-heal wounds. Ostomy Wound Manage 2003;49:52-66.
17. Miller MS, Lowery CA. Negative pressure wound therapy: “A rose by any other name.” Ostomy Wound Manage 2005;51:44-9.
by Michael S. Miller, DO, FACOS, CWS; Marta Ortegon, PA; Cheryl McDaniel, LPN; and Thomas Serena, MD, FACS, CWS
Table. Appropriate applications for negative pressure wound therapy (NPWT) (1) * Acute wounds * Partial and full-thickness burns * Surgically created wounds and surgical dehiscence Patients with other medical problems, i.e., diabetes, coronary artery disease, or renal disease, may be more susceptible to wound dehiscence and delayed wound healing. NPWT may provide increased wound stability. * Neuropathic (diabetic) ulcers * Venous or arterial insufficiency ulcer unresponsive to standard therapy * Traumatic wounds (i.e., flap or meshed graft) * Pressure ulcers (stage 3 or stage 4)
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