Negative-pressure wound therapy: a snapshot of the evidence

Topical negative pressure (TNP) is a mode of therapy used to encourage wound healing. It can be used as a primary treatment for chronic/complex wounds or as an adjunct to surgery. Based on the evidence to date, the clinical effectiveness of negative-pressure therapy is still unclear. Although case reports and retrospective studies have demonstrated enhanced wound healing in acute/traumatic wounds, chronic wounds, infected wounds, wounds secondary to diabetes mellitus, sternal wounds and lower limb wounds, there are very few randomised controlled trials, with unclear results. The evidence is lacking for the use of TNP therapy for other indications to enhance wound healing such as patients with decubitus ulcers, diabetes and peripheral vascular disease and to improve skin graft take. There have been, as yet, no quality-of-life studies available for negative-pressure therapy. Despite this, the usage of TNP has increased. This review provides an overview of clinical studies using TNP and proposes avenues for further research to elucidate the exact mechanism of TNP, in addition to large randomised controlled clinical trials of patients undergoing this therapy.     

The role of topical negative pressure in wound repair: Expression of biochemical markers in wound fluid during wound healing

The clinical effects of topical negative pressure therapy (TNP) on wound healing are well described in numerous articles. While the mechanism(s) of action are not completely understood, it is postulated that reduction of local and interstitial tissue edema, increased perfusion of the (peri-) wound area, changed bacterial composition, and mechanical stimulation of the woundbed contribute to the clinical success. Our hypothesis is that with the removal of excessive fluid, proteolytic enzymes negatively influencing the healing process are removed. Our aim was to assess whether the concentrations of albumin, matrixmetalloproteinase-9 (MMP-9), and tissue inhibitor of metalloproteinase (TIMP-1) were different between wounds treated with TNP and conventional gauze therapy. We analyzed wound fluid samples of 33 wounds treated with either TNP therapy ( n =15) or conventional therapy ( n =18) on albumin, pro- and activated MMP-9, TIMP-1, and the ratio of total MMP-9/TIMP-1. Albumin levels were found to increase significantly in acute wounds compared with chronic wounds; however, no difference could be found on comparing TNP with conventional therapy. We did find significantly lower levels of pro-MMP-9 and lower total MMP-9/TIMP-1 ratio in TNP-treated wounds during the follow-up of 10 days. These data strongly suggest that TNP therapy influences the microenvironment of the wound.     

Initial multi‐centre observations upon the effect of a new topical negative pressure device upon patient and clinician experience and the treatment of wounds

Topical Negative Pressure (TNP) has become an accepted intervention in wound healing with a growing body of scientific literature supporting the effectiveness of TNP across a wide variety of wound aetiologies. The range of TNP devices has also increased with perhaps the primary distinction being between those TNP devices that employ gauze or foam as a wound dressing. This study reports preliminary multi‐centre observations upon the use of a new gauze based TNP device in the treatment of wounds. Across 3 study centres twenty‐nine subjects were recruited to the study with 8 presenting with leg ulcers, 8 with pressure ulcers, 12 with acute or surgical wounds and 1 with a non‐healing burn injury. Wounds were then treated with the new TNP therapy for a maximum of 17 days (range 2–17 days). There appeared to be a trend for subjects with leg ulcers to be treated for longer (mean duration 12.9 days) compared to subjects with pressure ulcers (mean duration 6.5 days) or those with surgical wounds (mean duration 8.2 days). Given the relatively short duration of the TNP therapy no wound completely healed although 22/29 (75.9%) showed reductions in surface area per day of treatment with all but 1 pressure ulcer and 1 leg ulcer responding positively to treatment. While not an RCT, this and similar cohort studies may be central to the future selection of TNP devices given the increasing importance of the role of the user interface to reduce the likelihood of incorrect use and sub‐optimal outcomes.     

Topical negative pressure for the treatment of neonatal post-sternotomy wound dehiscence

The use of topical negative pressure (TNP) dressings for sternal wound dehiscence or mediastinitis in the neonatal population is rare. The majority of case reports have focused on wound healing as an endpoint and have not discussed the physiological advantage that TNP dressings may impart with regard to sternal stabilisation, improved respiratory function and early weaning from mechanical ventilation. We present a case of the use of TNP in neonatal post-sternotomy wound dehiscence and mediastinitis, from a UK perspective, with an emphasis on wound healing and physiological optimisation. As well as an improvement in sternal wound healing due to the local effects of the TNP system, serial arterial blood gas analysis revealed a significant improvement in systemic physiological parameters, including a reduction in pCO(2) in the period (days 20-31) after application of TNP (p<0.0001) compared to the period before where simple occlusive dressings were applied. Hydrogen ion concentration also significantly reduced in this period (p=0.0058). The use of the TNP system in association with systemic antibiotics successfully treated the mediastinitis. A sealed, controlled wound environment also allowed ease of nursing and an expedited return to care by the parents. We would recommend the consideration of TNP dressings in similar cases of neonatal and paediatric sternal wound dehiscence. Not only do we observe the local effects of improved wound healing, the systemic effects of improved lung function are also valuable in the early management of such complex cases.     

Managing the open wound: indications for topical negative pressure therapy

Surgeons frequently encounter open wounds. These include wounds which have failed to close by primary means, wounds which are left open at the outset and wounds which fail to heal by secondary intention in a timely manner. Wound healing is a complex process involving tissue repair and remodelling at the same time as removal of necrotic tissue and foreign material. Topical negative pressure (TNP) is a wound management technique which applies subatmospheric pressure to a healing wound in an attempt to facilitate healing. The potential mechanisms of action of TNP are poorly understood and may involve mechanical and biochemical effects. TNP has been suggested to be of value in a variety of settings, ranging from management of acute wounds to ischaemic and diabetic ulcers. There has been inadequate scientific evaluation of TNP, which has rarely been subjected to rigorous clinical trials or adequate effective economic evaluation. Although in general TNP does appear to be largely safe and acceptable to patients, the risk of fistulation associated with its use in the open abdomen remains to be determined and is currently being evaluated by a national audit.     

Vessel transformation in chronic wounds under topical negative pressure therapy: an immunohistochemical analysis

The underlying physiological mechanism of topical negative pressure (TNP) therapy is not yet completely understood. This prospective clinical study aims to clarify a potential influence of TNP therapy on vessel proliferation and hypoxia in chronic wounds. TNP was applied on chronic wounds of 16 patients (?125 mmHg) to prepare them for a plastic‐surgical reconstruction using free or pedicled flaps. Tissue biopsies were taken from the wound edge and wound bed at different time points. All samples were stained with haematoxylin and eosin, hypoxia‐induced factor‐1α and endothelial cell markers (CD31 and CD34) for the immunohistological analysis of inflammation, hypoxia and vessel proliferation. Between day 5 and day 8 of treatment, a considerable increase in blood vessel density could be observed, reaching a maximum of approximately 200% in contrast to the vessel density prior to treatment. In addition, the number of hypoxic and inflammatory cells was found to be increased at particular time points. This study demonstrates a stimulating effect on vessel proliferation under TNP treatment. TNP appears to support (neo‐) angiogenesis and transformation of chronic non‐healing wounds in a physiological wound healing process when combined with surgical debridement. This effect underlines the positive influence of TNP in the treatment of chronic wounds as shown by various clinical reports.     

Activated protein C to heal pressure ulcers

Pressure ulcers present a major clinical challenge, are physically debilitating and place the patient at risk of serious comorbidities such as septic shock. Recombinant human activated protein C (APC) is an anticoagulant with anti‐inflammatory, cytoprotective and angiogenic effects that promote rapid wound healing. Topical negative pressure wound therapy (TNP) has become widely used as a treatment modality in wounds although its efficacy has not been proven through randomised controlled trials. The aim of this study was to determine the preliminary efficacy and safety of treatment with APC for severe chronic pressure sores with and without TNP. This case presentation describes the history, management and outcome of two patients each with a severe chronic non‐healing pressure ulcer that had failed to respond to conventional therapy. TNP was added to conservative management of both ulcers with no improvement seen. Then local application of small doses of APC was added to TNP and with conservative management, resulted in significant clinical improvement and rapid healing of both ulcers, displaying rapid growth of vascular granulation tissue with subsequent epithelialisation. Patients tolerated the treatment well and improvements suggested by long‐term follow‐up were provided. Randomised placebo‐controlled double blind trials are needed to quantify the efficacy, safety, cost‐effectiveness, optimal dose and quality of life changes seen from treatment with APC.     

A review of topical negative pressure therapy in wound healing: sufficient evidence?

Background

Topical negative pressure (TNP) therapy has become a useful adjunct in the management of various types of wounds. However, the TNP system still has characteristics of a “black box” with uncertain efficacy for many users. We extensively examined the effectiveness of TNP therapy reported in research studies.

Data sources

A database search was undertaken, and over 400 peer-reviewed articles related to the use of TNP therapy (animal, human, and in vitro studies) were identified.

Conclusions

Almost all encountered studies were related to the use of the commercial VAC device (KCI Medical, United States). Mechanisms of action that can be attributed to TNP therapy are an increase in blood flow, the promotion of angiogenesis, a reduction of wound surface area in certain types of wounds, a modulation of the inhibitory contents in wound fluid, and the induction of cell proliferation. Edema reduction and bacterial clearance, mechanisms that were attributed to TNP therapy, were not proven in basic research.     

Management of intractable sternal wound infections with topical negative pressure dressing

BACKGROUND: Sternal osteomyelitis after cardiac surgery is a life-threatening complication. The potential spread of infection into the mediastinum, involving the prosthetic valve, grafts, and suture lines, makes this an extremely serious complication confronting both cardiac and plastic surgeons. Aim: Topical negative pressure (TNP) dressing has been proven to be effective for wound healing. We want to take advantages of this equipment to improve the results of intractable sternal wound infection. The results are discussed. METHODS: From December 1996 to July 2002, 25 patients with sternal wound infections were treated at Kaohsiung Medical University Hospital. Nine patients suffering intractable sternal osteomyelitis were managed with debridement and TNP dressings. These patients received 1-3 debridements (an average of 2.2 debridements), and the average TNP dressing treatment period was 20.2 days (ranging from 3 to 43 days). After management, the infections were controlled and healthy vascularized wounds were achieved. Then, flap reconstruction could be performed for complete wound closure. Seven of the nine patients survived, and there was no recurrence of sternal osteomyelitis during follow-up period (ranging from 5 to 70 months). CONCLUSION: The advantages of applying TNP dressings in cases of intractable sternal wound infections include (1) protecting the underlying mediasternal structure from infection, (2) permitting delayed sternal closure to avoid cardiac compression induced compromised cardiopulmonary function, (3) possibility of repeated wound inspection and bedside debridement, (4) cost-effectiveness of wound care, and (5) providing an option to promote sternal wound secondary healing for patients in poor physical condition.     

Topical negative pressure for treating chronic wounds: a systematic review.

Some wounds take a long time to heal, fail to heal or recur, causing significant pain and discomfort to the patient and cost to the National Health Service. This review assesses the effectiveness of topical negative pressure (TNP) in treating chronic wounds. The Cochrane Wounds Group Specialised Trials Register was searched for randomised controlled trials (RCTs) that evaluated the effectiveness of TNP on chronic-wound healing. Eligibility for inclusion, data extraction and details of trial quality were conducted by two reviewers independently. A narrative synthesis of results was undertaken as only two small trials, with different outcome measures, fulfilled the selection criteria. Trial 1 considered any type of chronic wound, trial 2 considered diabetic foot ulcers. Both trials compared TNP with saline-gauze dressings. Trial 1 reported a statistically significant difference in the percentage change in wound volume after 6 weeks, in favour of TNP. Trial 2 reported a difference in the number of days to healing and a difference in the percentage change in wound surface area after 2 weeks, in favour of TNP. These two small trials provide weak evidence to suggest that TNP may be superior to saline-gauze dressings in terms of wound healing. However, due to the small sample sizes and the methodological limitations of the studies, these findings must be interpreted with extreme caution. The effects of TNP on cost, quality of life, pain and comfort were not reported. It was not possible to determine the optimum TNP regimen. Further high-quality RCTs that address these issues are required.     

Topical negative therapy and vacuum assisted closure. New strategies and devices in surgical reconstruction

Topical negative pressure (TNP) has been introduced in complex surgical reconstruction and difficult wound healing, having proven to be effective in both drainage of wound secretions and calling for a new, sterile granulating tissue. In the last 15 years many reports have been focusing on TNP in different surgical specialties (orthopedic surgery in exposed fractures, general surgery in eventration, cardiothoracic surgery in sternal dehiscences, plastic surgery in difficult wounds and pressure sores). The authors report their personal experience being among the first Units to use TNP systematically in Italy.     

Topical negative pressure wound therapy: a review of its role and guidelines for its use in the management of acute wounds

Over the past two decades, topical negative pressure (TNP) wound therapy has gained wide acceptance as a genuine strategy in the treatment algorithm for a wide variety of acute and chronic wounds. Although extensive experimental and clinical evidence exists to support its use and despite the recent emergence of randomised control trials, its role and indications have yet to be fully determined. This article provides a qualitative overview of the published literature appertaining to the use of TNP therapy in the management of acute wounds by an international panel of experts using standard methods of appraisal. Particular focus is applied to the use of TNP for the open abdomen, sternal wounds, lower limb trauma, burns and tissue coverage with grafts and dermal substitutes. We provide evidence-based recommendations for indications and techniques in TNP wound therapy and, where studies are insufficient, consensus on best practice.     

Combination of activated protein C and topical negative pressure rapidly regenerates granulation tissue over exposed bone to heal recalcitrant orthopedic wounds

Chronic wounds arising from orthopedic surgery present a major clinical challenge. Osteomyelitis may develop from polymicrobial infection, which can be unresponsive to treatment and lead to amputation. Topical negative pressure (TNP) is an effective treatment in wound management and is now used worldwide. Activated protein C (APC) is an anticoagulant with cytoprotective and healing properties. The aim of this study was to determine whether combined treatment of TNP and APC was tolerated and was efficacious for treatment of difficult-to-treat wounds. Four patients who presented to Royal North Shore Hospital with wounds that were not responsive to conventional therapy were studied. All cases showed a marked reduction in wound size and depth within 1 week of starting treatment and progressively improved over time. There was a remarkable increase in the volume of granulation tissue. After treatment, wounds either completely closed or provided sufficient granulation tissue to allow split-thickness skin grafting. The treatment was well tolerated, and the patients were able to be managed on out-patient basis. Long-term follow-up suggested that this treatment prevented osteomyelitis. This innovative treatment is very promising and may significantly increase quality of care for patients with recalcitrant orthopedic wounds. A randomized, placebo-controlled double blind trial is required to further determine the efficacy of APC plus TNP.     

Development of an evidence-based protocol for care of pilonidal sinus wounds healing by secondary intent using a modified reactive Delphi procedure. Part one: the literature review*

This article is in two parts. The overall aim of this section was to review the literature in relation to pilonidal sinus wounds (PSW) healing by secondary intent for a Master's of Science in Wound Healing and Tissue Repair thesis. The purpose of the literature review was to determine if an evidence-based guideline or consensus document existed for the care of these wounds, and if not, to determine the topics from which to develop items for the first round of a modified reactive Delphi questionnaire. Part two will describe the iterative process, the analysis and the results. The review found no best practice guidelines concerning PSW, and only one clinical pathway. Seventeen areas of interest were identified that may contribute to optimal healing conditions or to delayed healing. These included microbiology of infected PSW, signs and symptoms of localised or deeper (spreading) chronic wound infection, swab for c&s, role of topical antiseptics or antimicrobials, systemic antibiotics, local wound interventions, optimal positioning, wound cleansing, principles of moist wound healing/dressing selection, topical negative pressure (TNP) therapy, peri-wound skin decontamination and depilation, pain control, physical activities, optimal nutrition and patient education.     

Topical negative pressure therapy: mechanisms and indications

Topical negative pressure (TNP) therapy has emerged as a high-technology, microprocessor-controlled physical wound-healing modality. Complex effects at the wound-dressing interface following application of a controlled vacuum force have been documented. These include changes on a microscopic, molecular level and on a macroscopic, tissue level: interstitial fluid flow and exudate management, oedema reduction, effects on wound perfusion, protease profiles, growth factor and cytokine expression and cellular activity, all leading to enhanced granulation tissue formation and improved wound-healing parameters. Primary indications for clinical use have been documented and include traumatic wounds, open abdominal wounds, infected sternotomy wounds, wound bed preparation, complex diabetic wounds and skin-graft fixation. Whilst this therapy now forms an essential part of the wound healing armamentarium, extensive clinical trials are recommended to confirm efficacy and delineate its optimum use.     

The effectiveness of topical negative pressure in the treatment of pressure ulcers: a literature review

The objective of the study was to gain insight into the effectiveness of vacuum-assisted closure (VAC) therapy or, more particularly, topical negative pressure (TNP) in the treatment of pressure ulcers. We carried out a systematic search in Medline, Embase and Cinahl for Randomized Clinical Trials (RCTs) involving topical negative pressure in pressure ulcers over the period 1992–2007. Five RCTs were included. Two studies dealt exclusively with pressure ulcers. No significant differences in wound healing were found in these studies. Three other studies (mixed etiology of wounds) did show significant differences in wound healing, in the decrease of wound treatment time, and in the decrease in number of bacteria. The quality of these studies, both in terms of methodology and otherwise, did not always match with the scientific standard. Moreover, these studies lacked subgroup analyses. The analyzed studies described positive effects of TNP, although both the control treatment and the end points varied in these studies. On the basis of the systematic assessment of these five RCTs, the conclusion is that TNP has not proven to be more effective than various control interventions. The differences between and within the studies in terms of control interventions, the differences in randomization and a number of weaknesses in the analyses do not allow a good comparison. The main recommendations for follow-up studies include: randomization of patients rather than of wounds, a homogeneous patient population, the use of a single well-defined and procedurally documented control intervention, and prior calculation of the random sample size.     

The effects of Panafil when using topical negative pressure to heal an infected sternal wound

A wound that became infected a few weeks after bypass surgery responded well to a treatment regimen combining TNP with application of an enzymatic agent. The patient had diabetes mellitus, which slows healing and increases infection risk.     

PR24EFFECTS OF COMBINED TOPICAL NEGATIVE PRESSURE (TNP) AND ANTISEPTIC INSTILLATION ON PSEUDOMONAS BIOFILM

Purpose TNP in the form of V.A.C. dressings have been successfully used to enhance chronic wound healing. An in vitro model of the chronic wound biofilm was created to test the effects of TNP with and without concurrent antimicrobial drug instillation on biofilms. Method A P.aeruginosa biofilm model was constructed in vitro. Continuous TNP and TNP combined with varying frequencies of betadine instillation were tested on the biofilm model for 24 hours. Outcome parameters measured included viable bacterial count, fluorescent microscopy, confocal laser scanning microscopy, and electron microscopy. Statistical analysis was performed using ANOVA and MANOVA in SPSS 13.0. Results Bacterial biofilms, when exposed to TNP alone, showed a 42% decrease in viable count; while exposure to betadine alone showed a reduction of up to 84%. Combined TNP and antiseptic instillation increased the bacteriocidal effect to 99.7% (p < 0.001). Exposure to TNP also resulted in a decrease in biofilm thickness, and diffusion distance, with an increase in surface area‐to‐volume ratio (p = 0.005, 0.002, and 0.009 respectively). Conclusion TNP alone showed a modest effect on the reduction of bacterial biofilm. More importantly it appeared to compress and fragment the overall biofilm architecture. This physical deformity in turn led to more effective drug penetration into the highly resistant biofilm community. The result was an approximate 100 fold enhancement of bacteriocidal effect when betadine instillation was combined with TNP as compared to betadine alone.     

No hypoperfusion is produced in the epicardium during application of myocardial topical negative pressure in a porcine model

Background  

Topical negative pressure (TNP), commonly used in wound therapy, has been shown to increase blood flow and stimulate angiogenesis in skeletal muscle. We have previously shown that a myocardial TNP of -50 mmHg significantly increases microvascular blood flow in the myocardium. When TPN is used in wound therapy (on skeletal and subcutaneous tissue) a zone of relative hypoperfusion is seen close to the wound edge. Hypoperfusion induced by TNP is thought to depend on tissue density, distance from the negative pressure source, and the amount negative pressure applied. When applying TNP to the myocardium, a significant, long-standing zone of hypoperfusion could theoretically cause ischemia, and negative effects on the myocardium. The current study was designed to elucidate whether hypoperfusion was produced during myocardial TNP.     

Adverse alteration of wound flora with topical negative-pressure therapy: a case report.

Topical negative pressure (TNP) has achieved widespread use in the treatment of problematic wounds. We report the case of a patient treated with TNP for groin-wound dehiscence following inguinal block dissection. During treatment, clinical signs of sepsis developed, in association with a progressively worsening anaerobic wound infection. This infection settled with antibiotic therapy and cessation of TNP treatment. We postulate that the air-free environment created by TNP potentiated the growth of the anaerobic bacteria, resulting in significant sepsis, and therefore recommend close surveillance of bacterial flora while using this therapy, particularly in susceptible patients.