Negative Pressure Wound Therapy: “A Rose by Any Other Name”

    A recent article by Sibbald¹ reviewed the findings of a Canadian consensus conference convened to address the use of Vacuum Assisted Closure® (V.A.C.® Therapy, KCI USA, San Antonio, Tex.) in wound management. Sibbald states the goal of the conference was to describe, “best practice statements that serve to guide treatment approaches and stimulate further study.”¹ Although Sibbald acknowledged the need for more prospective, randomized studies to guide the use of negative pressure wound therapy (NPWT) in chronic wounds, his review was limited by the fact that he only described the use of a single product rather than the concept of NPWT.

Although V.A.C.® Therapy has achieved impressive results in appropriate wounds, the literature has failed to address other conceptualizations and incarnations of NPWT. This omission limits “thinking outside the box.” As everyone knows, not every duplication machine is a Xerox (Xerox Corporation, Stamford, Conn.) and not every flavored gelatin product is Jell-O (Kraft Foods, Northfield, Ill.). Therefore, the term V.A.C. should not be automatically synonymous with NPWT.

    Presently, considerable legal parry and thrust has occurred as KCI seeks to maintain its proprietary hold on this modality. The general question arises: Is negative pressure (suction) proprietary? If wound care specialists are to push the limits in their endeavors to heal chronic wounds more efficiently and more cost effectively, the issues, concerns, and conditions that are not addressed by current technology must be identified and newer, more efficient technologies created. More specific questions regarding NPWT and, particularly, the V.A.C. are: 1) What are the limitations of the current incarnation? 2) Can these limitations be overcome using the currently available technology? 3) If not, could currently available technologies be used to overcome limitations? 4) If the technology is not yet available, how will it be developed?

Literature Review

    NPWT as we know it. In 1997, Morykwas and Argenta^2-4 published three landmark articles regarding their experience with a “new method for wound control and treatment.”² A system was described where subatmospheric pressure^2,3 was applied through a closed system to an open wound for periods of 48 hours. Subatmospheric pressure was directed at the surface of the wound through an interface between the wound surface and a polyurethane sponge to allow for distribution of the negative pressure using either a constant or intermittent mode based on the clinical experience of the physician. From this technology, the V.A.C.® System evolved.

    Negative pressure wound therapy is thought to promote wound healing through multiple actions — eg, removing exudate from wounds to help establish fluid balance,⁵ providing a moist wound environment,² and removing slough⁵; and potentially decreasing wound bacterial burden,² reducing edema and third-space fluids, increasing blood flow to the wound,^2,3,5 increasing growth factors, and promoting white cells and fibroblasts within the wound.⁶ Barker and Kaufman⁶ reported a 7-year experience with what was called “VAC pack” therapy in which the wound edges were attached to a circumferential plastic bag with small perforations that allowed drainage to escape. Suction drains were placed over the plastic to collect fluid via wall suction. This differs from current V.A.C.® Therapy in that negative pressure was not applied to the wound. The vacuum was used only as a method to collect fluid from the wound in a continuous manner.

    International incarnations. An aggressive search of the literature uncovered a series of five articles published in the Russian medical literature. Two of the articles were published in 1986 (11 years before the Morykwas and Argenta articles), one in 1987, and one each in 1991 and 1998. These articles have been colloquially described as “The Kremlin Papers.”^7-11

    The first, an article published by Kostiuchenok et al⁷ in 1986, discusses the failure of surgical debridement to significantly reduce microbial counts in the tissue of purulent wounds. The authors made the specific point that, “The vacuum method has been used for the preparation of persistent nonhealing wounds and trophic ulcers for autografting”⁷ with specific source citations identified in the Russian literature. This study included 221 subjects with purulent wounds of various etiologies. Subjects were divided into three treatment groups: Group 1 included 22 subjects who received vacuum treatment before and after surgical debridement; Group 2 included 94 subjects who received treatment only after surgical debridement; and Group 3 (control) comprised 105 subjects who received only surgical debridement (no vacuum treatment). Vacuum treatment was applied using an external funnel device (25 mm to 30 mm in diameter) placed tightly against the wound at a pressure of -100 mm Hg and moved along the entire wound area, removing foreign bodies, blood clots, and detritus. Average treatment times ranged from 5 to 10 minutes. Vacuum treatment was stopped according to subjective criteria of no visible contamination remaining in the wound and brisk capillary hemorrhage appearing over the wound surface. “Biological analysis of the microbe count per 1 g of wound tissue”¹⁰ was performed following vacuum treatment. The authors’ most significant conclusion was that negative pressure treatment of purulent wounds in combination with surgical debridement significantly reduced the bacterial burden within the wound and resulted in improved wound healing.

    That same year, Davydov et al⁸ published an article that discussed the use of vacuum therapy combined with surgical debridement in patients with purulent lactation mastitis. Although this condition is rarely encountered in the US, it was not uncommon to the Soviet Health Care System. Russian physicians recognized the prolonged healing times and poor outcomes when surgical therapy alone was used in the treatment of this condition. Of the 229 subjects with purulent lactation mastitis evaluated, 106 were treated using surgical debridement of the suppurative focus and subsequent intra-operative insertion of a drainage tube into the wound to a depth of 1.5 cm to 2 cm above the deepest aspect of the wound base. The entire wound was then completely encompassed by an appropriately shaped chamber to allow for the application of 0.8 to 1.0 atmospheres (ATA) of negative pressure to the wound bed for 20 minutes. Negative pressure therapy was continued twice daily for 2.5 to 3 hours. Interestingly, patients were able to clamp off the tubing to the sealed device at different intervals to allow for mobility without any apparent loss of negative pressure in the system. This course of therapy was continued for 5 to 6 days. A comparison of serum and blood chemistries of the patients before and after therapy showed that patients receiving vacuum therapy demonstrated increased complement activity in CH50 (Total Hemolytic Complement) – a system of cell membrane associated and plasma proteins which, when activated, produce inflammatory mediators vital to the normal function of the immune system; a relative increase in T-cells; improved antibody titers to the dominant microbe; and decreased levels of IgG and IgA with increased levels of IgM. These findings suggested that vacuum therapy applied at the time of debridement and continued at intermittent intervals for several days reduced bacterial wound load and septic complications, reduced the time of wound healing, normalized the immune process, and significantly reduced wound cicatrization.

    Subsequently in 1987, Usopov and Yepifanov⁹ published their findings regarding the effects of wound drainage after surgical intervention. Until this time, no uniform opinions were available regarding when to use vacuum therapy, what the duration of the therapy should be, or what amount of negative pressure would be most beneficial. Using wounds created in a rabbit model, the authors applied varying levels of negative pressure along with passive drainage as a control in an attempt to study the effects of active wound drainage in a clinical setting. The authors determined that a pressure of -75 mm Hg to -80 mm Hg had the most distinct effect on increasing wound drainage with little or no hemorrhage of coagulated vessels. As the pressure increased to -120 mm Hg to -125 mm Hg, extensive tissue edema was observed with separation of the adjacent muscle fibers secondary to the edema. Additionally, inflammatory infiltration and fresh hemorrhages from coagulated vessels were identified as pressures approached -160 mm Hg to -170 mm Hg. At levels of -35 mm Hg to -40 mm Hg, histological evaluation of the tissue identified increased wound edema, cellular infiltration, insignificant edema of the tissues around the drain, and only isolated fresh hemorrhages. The authors concluded that damaging effects of active wound drainage on tissues adjacent to wounds occurred at pressures below -80 mm Hg. The authors also found as pressures of -75 mm Hg to -80 mm Hg or less were utilized, hemorrhage of the coagulated vessels decreased. Within the same study, the authors also evaluated 1,616 subjects with varying types of wounds. Sterile wounds were treated with active wound drainage at a level of -70 mm Hg to -80 mm Hg continuously for 2 to 3 days. In wounds with obvious purulence, active debridement was combined with antibiotic irrigation and “general” antibacterial therapy. Continuous vacuum suction at a pressure of -30 mm Hg to -40 mm Hg was applied with wound irrigation performed three to six times per day. Subjects continued on this regimen for 6 to 8 days until signs of local inflammation in the wound resolved, drainage was no longer purulent, and patients were afebrile. Complication rates for all patients then were compared. The authors concluded that to avoid tissue damage negative pressure in active drainage systems should not exceed -80 mm Hg; lower pressures were less likely to demonstrate postoperative hemorrhage.

    In 1988, Davydov et al¹⁰ evaluated the bacteriologic and cytologic properties of purulent wounds. A perforated drain was placed into the depths of purulent wounds after surgical incision and drainage in 226 patients. A wound-encompassing hemispherical chamber device was attached to a vacuum source along with a deeper drain. This allowed equal distribution of negative pressure to the walls of the wound tract and the surrounding tissues while pressures of -1 to -1.5 ATA were applied. In this group of patients, the therapy was started the day after aggressive surgical debridement and applied for 1 hour per day for 6 days. A comparison group of 212 subjects received aggressive surgical debridement only. Tissue biopsies were obtained and compared for the absolute number of macrophages, fibroblasts, mastocytes, neutrophils, and mononuclear cells. The authors concluded that a course of vacuum therapy in combination with aggressive debridement shortened the purulent inflammatory process and decreased local bacterial counts more effectively than debridement alone. Additionally, in both sets of wounds, when vacuum therapy was applied using a deep drain and a wound-encompassing chamber at pressures of -1 to -1.5 ATA, faster wound closure as well as “obliteration of the wound cavity”¹⁰ was promoted.

    A review article¹¹ in 1991 discussed different modalities (eg, fluid pulse jets, enzymatic debridement, laser and ultrasound necrolysis, and forced suction) used to treat purulent wounds after aggressive debridement. This retrospective review included 744 subjects with purulent wounds — 406 subjects had vacuum therapy after surgical debridement and 338 subjects received surgical debridement alone. With the exception of suction therapy, the authors felt that these various modalities were not “universal enough to affect all elements of the biological system of healing during the inflammatory phase.” After evaluating multiple serological, bacterial, and tissue/cellular effects of the vacuum therapy, the authors observed “a pronounced immunocorrecting effect.”¹¹ The reduced number of infectious wound complications, decreased repeat surgeries, reduced purulent related fevers, and decreased sepsis over traditional sharp debridement alone was consistent with this finding. Additionally, vacuum therapy was used successfully as a preventative measure in the treatment of sterile postoperative wounds with increased risk of infectious complications. Based on the effects observed, vacuum therapy appears to promote a biologic progression of wound healing for debrided purulent and sterile wounds. The application of negative pressure to these wounds clearly had a positive effect on the inflammatory phase of wound healing, a necessary part of wound process management.

    Meanwhile, in 1989 Americans Chariker and Jeter et al¹² published their experience utilizing NPWT in the treatment of incisional and cutaneous fistulae. From 1984 to 1986, seven patients with eight fistulae were treated with what was called a “closed suction wound drainage system.”¹² Six of the fistulae were enterocutaneous and one was renalcutaneous. Following irrigation of the wound, a moist 2" x 2" gauze was placed into the wound base and a Jackson-Pratt Mini Snyder flat drain was placed over the gauze. Fluffed moist gauze was then placed over the Jackson-Pratt drain. Finally, a bio-occlusive dressing was placed over the wound, creating an air-tight seal. The Jackson-Pratt drain was connected to continuous suction at approximately -60 mm Hg to -80 mm Hg pressure. The system was changed every 3 to 5 days. All wounds treated with this modality closed in a mean time of 16 days (range 8 to 23 days). The estimated the cost of this therapy that year was approximately $205 per week versus $1,400 per week for conventional dressing and dressing changes.

Discussion

    Wound healing is a complex, multifaceted event that depends on a balance between the components of the wound microenvironment and temporal events that occur in the cellular milieu, all of which are intertwined. In a complex wound, small changes in the temporal, biochemical, or physical properties of the healing process may mean the difference between progression toward healing or nonhealing. Currently, the V.A.C.® System is the dominant form of NPWT used in North America. Although the V.A.C. demonstrates impressive results in chronic, subacute, and acute wounds when used appropriately, several discrepancies between the literature of Morykwas and Argenta and the newly discovered “Kremlin Papers”^7-11 must be noted.

    In a porcine model, Morykwas and Argenta² demonstrated that peak blood flow to a wound occurred at a negative pressure of -125 mm Hg and that blood flow was depressed below baseline values at negative pressures of -400 mm Hg and greater. Usopov and Yepifanov⁹ utilized a rabbit model that identified a negative pressure of -75 mm Hg to -80 mm Hg as optimal for wound healing; additionally, they demonstrated new tissue hemorrhage of previously coagulated vessels with negative pressures below -120 mm Hg to -125 mm Hg. These results confound the issue regarding most beneficial NPWT intensity.

    The Morykwas and Argenta² literature states that optimal results were obtained when NPWT was applied continuously for the first 48 hours and subsequently applied in a cyclical manner (5 minutes on, 2 minutes off). Davydov et al⁸ utilized negative pressure therapy twice daily for only 2.5 to 3 hours. This raises numerous questions: Is intermittent negative pressure therapy equivalent to continuous negative pressure wound therapy? Is intermittent interval therapy as efficacious as 24-hour continuous therapy? If intermittent therapy is just as efficacious, will patients be more compliant? Would this make NPWT more cost effective? If continuous therapy is found superior, a consensus on how often the negative pressure wound dressings need to be changed is needed. Sibbald et al¹ offered no clear consensus when dealing with the question of continuous versus intermittent therapy and frequency of dressing change.

    The complexity of wound healing requires that to optimize NPWT, researchers and clinicians must address these unresolved issues through further study and clinical correlation. Improved negative pressure incarnations and different treatment strategies may result in improved, more efficient, and more cost effective wound care. Negative pressure wound therapy is still in its infancy — the door of opportunity is wide open for new research and new solutions to old wound care problems.

Conclusion

    The question is not whether NPWT is beneficial in wound healing. Numerous case studies and articles have documented its effectiveness. Rather, the question is whether today’s most commonly used method for applying NPWT is the safest and most effective method available. Determining the parameters for pressure intensity, duration of treatment, interval between treatments, mode of application, and timing of application will allow clinicians to provide the most efficient and cost effective therapy. No single entity holds a mandate for NPWT — no single modality will suffice in all situations. Experimentation, evaluation, and personal experience will combine to propel thinking “outside of the box” toward improving patient outcomes. The “Kremlin Papers”^7-11 and the alternative NPWT concepts they address have existed for many years and raise many questions about the currently accepted dogma of V.A.C.® Therapy. To paraphrase The Bard, would a rose by any other name still suck as well?

1. 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(11):52–66.

2. Morykwas MJ, Argenta LC, Shelton-Brown EI, et al. Vacuum-assisted closure: a new method for wound control and treatment: animal studies and basic foundation. Ann Plast Surg. 1997;38:553–562.

3. Argenta LC, Morykwas MJ. Vacuum-assisted closure: a new method for wound control and treatment: clinical experience. Ann Plast Surg. 1997;38:563–577.

4. Morykwas MJ, Argenta LC. Nonsurgical modalities to enhance healing and care of soft tissue wounds. J Southern Orthopedic Association. 1997:6:279–288.

5. Zarogen A. Nutritional assessment and intervention in the person with a chronic wound. In: Krasner DL, Rodeheaver GT, Sibbald RG, eds. Chronic Wound Care: A Clinical Source Book for Healthcare Professionals, Third Edition. Wayne, Pa.; Health Management Publications, Inc.;2001:117–126.

6. Barker DE, Kaufman HJ, et al. Vacuum pack technique of temporary abdominal closure: a 7-year experience with 112 patients. J Trauma Injury Infection Crit Care. 2000:48(2):201–206.

7. Kostiuchenok II, Kolker VA, Karlov VA. The vacuum effect in the surgical treatment of purulent wounds. Vestnik Khirurgii. 1986:9:18–21.

8. Davydov YA, Malafeeva AP, Smirnov AP. Vacuum therapy in the treatment of purulent lactation mastitis. Vestnik Khirurgii. 1986:9:66–70.

9. Usupov YN, Yepifanov MV. Active wound drainage. Vestnik Khirugii. 1987:4:42-45.

10. Davydov YA, Larichev KG, et al.: The bacteriological and cytological assessment of vacuum therapy of purulent wound. Vestnik Khirugii. 1988: 10: 48–52.

11. Davydov, YA; Larichev KG, Abramov AY. Concepts for clinical biological management of the wound process in the treatment of purulent wounds using vacuum therapy. Vestnik Khirugii. 1991:2:132–135.

12. Chariker ME, Jeter KF, Tintle TE. Effective management of incisional and cutaneous fistulae with closed suction wound drainage. Contemporary Surgery. 1989:34:59–63.