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1.  Macroscopic changes during negative pressure wound therapy of the open abdomen using conventional negative pressure wound therapy and NPWT with a protective disc over the intestines 
BMC Surgery  2011;11:10.
Higher closure rates of the open abdomen have been reported with negative pressure wound therapy (NPWT) than with other wound management techniques. However, the method has occasionally been associated with increased development of fistulae. We have previously shown that NPWT induces ischemia in the underlying small intestines close to the vacuum source, and that a protective disc placed between the intestines and the vacuum source prevents the induction of ischemia. In the present study we compare macroscopic changes after 12, 24, and 48 hours, using conventional NPWT and NPWT with a protective disc between the intestines and the vacuum source.
Twelve pigs underwent midline incision. Six animals underwent conventional NPWT, while the other six pigs underwent NPWT with a protective disc inserted between the intestines and the vacuum source. Macroscopic changes were photographed and quantified after 12, 24, and 48 hours of NPWT.
The surface of the small intestines was red and mottled as a result of petechial bleeding in the intestinal wall in all cases. After 12, 24 and 48 hours of NPWT, the area of petechial bleeding was significantly larger when using conventional NPWT than when using NPWT with the protective disc (9.7 ± 1.0 cm2 vs. 1.8 ± 0.2 cm2, p < 0.001, 12 hours), (14.5 ± 0.9 cm2 vs. 2.0 ± 0.2 cm2, 24 hours) (17.0 ± 0.7 cm2 vs. 2.5 ± 0.2 cm2 with the disc, p < 0.001, 48 hours)
The areas of petechial bleeding in the small intestinal wall were significantly larger following conventional NPWT after 12, 24 and 48 hours, than using NPWT with a protective disc between the intestines and the vacuum source. The protective disc protects the intestines, reducing the amount of petechial bleeding.
PMCID: PMC3095529  PMID: 21529362
negative pressure wound therapy; open abdomen; macroscopic changes; intestinal wall
2.  Microvascular blood flow response in the intestinal wall and the omentum during negative wound pressure therapy of the open abdomen 
Higher closure rates of the open abdomen have been reported with negative pressure wound therapy (NPWT) compared with other wound therapy techniques. However, the method has occasionally been associated with increased development of intestinal fistulae. The present study measures microvascular blood flow in the intestinal wall and the omentum before and during NPWT.
Six pigs underwent midline incision and application of NPWT to the open abdomen. The microvascular blood flow in the underlying intestinal loop wall and the omentum was recorded before and after the application of NPWT of −50, −70, −100, −120, −150, and −170 mmHg respectively, using laser Doppler velocimetry.
A significant decrease in microvascular blood flow was seen in the intestinal wall during application of all negative pressures levels. The blood flow was 2.7 (±0.2) Perfusion Units (PU) before and 2.0 (±0.2) PU (*p < 0.05) after application of −50 mmHg, and 3.6 (±0.6) PU before and 1.5 (±0.2) PU (**p < 0.01) after application of −170 mmHg.
In the present study, we show that negative pressures between −50 and −170 mmHg induce a significant decrease in the microvascular blood flow in the intestinal wall. The decrease in blood flow increased with the amount of negative pressure applied. One can only speculate that a longstanding decreased blood flow in the intestinal wall may induce ischemia and secondary necrosis in the intestinal wall, which, theoretically, could promote the development of intestinal fistulae. We believe that NPWT of the open abdomen is a very effective treatment but could probably be improved.
PMCID: PMC3281201  PMID: 21938450
Negative pressure wound therapy; Open abdomen; Microvascular blood flow; Intestinal wall; Omentum
3.  Negative Pressure Wound Therapy for the Treatment of the Open Abdomen and Incidence of Enteral Fistulas: A Retrospective Bicentre Analysis 
Introduction. The open abdomen (OA) is often associated with complications. It has been hypothesized that negative pressure wound therapy (NPWT) in the treatment of OA may provoke enteral fistulas. Therefore, we analyzed patients with OA and NPWT with special regard to the occurrence of intestinal fistulas. Methods. The present study included all consecutive patients with OA treated with NWPT from April 2010 to August 2011 in two hospitals. Patients' demographics, indications for OA, risk factors, complications, outcome and incidence of fistulas before, during and after NPWT were recorded. Results. Of 81 patients with OA, 26 had pre-existing fistulas and 55 were free from a fistula at the beginning of NPWT. Nine of the 55 patients developed fistulas during (n = 5) or after NPWT (n = 4). Seventy-five patients received ABThera therapy, 6 patients other temporary abdominal closure devices. Only diverticulitis seemed to be a significant predisposing factor for fistulas. Mortality was slightly lower for patients without fistulas. Conclusion. The present study revealed no correlation between occurrence of fistulas before, during, and after NWPT, with diverticulitis being the only risk factor. Fistula formation during NPWT was comparable to reports from literature. Prospective studies are mandatory to clarify the impact of NPWT on fistula formation.
PMCID: PMC3830879  PMID: 24285953
4.  Application of negative pressure wound therapy in patients with wound dehiscence after abdominal open surgery: a single center experience 
Since the 1990's, negative pressure wound therapy (NPWT) has been used to treat soft tissue defects, burn wounds, and to achieve skin graft fixation. In the field of abdominal surgery, the application of NPWT is increasing in cases with an open abdominal wound requiring temporary wound closure and a second look operation. In the present study, the authors analyzed patients that underwent NPWT for postoperative wound dehiscence.
The computerized records of patients that had undergone an abdominal operation from November 2009 to May 2012 were retrospectively analyzed.
The number of total enrolled patients was 50, and 30 patients (60%) underwent an emergency operation. Diagnoses were as follows: panperitonitis or intra-abdominal abscess (24 cases, 48%), intestinal obstruction (10 cases, 20%), cancer (7 cases, 14%), mesentery ischemia (3 cases, 6%), and hemoperitoneum (1 case, 2%). NPWT was applied at a mean of 12.9 ± 8.2 days after surgery and mean NPWT duration was 17.9 days (2 to 96 days). The 11 patients (22%) with unsuccessful wound closure had a deeper and more complex wound than the other 39 patients (78%) (90.9% vs. 38.5%, P = 0.005). There were two complication cases (4%) due to delayed wound healing.
Most patients recovered well due to granulation formation and suturing. NPWT was found to be convenient and safe, but a prospective comparative study is needed to confirm the usefulness of NPWT in patients whose wounds are dehisced.
PMCID: PMC3791361  PMID: 24106685
Negative pressure wound therapy; Vacuum-assisted closure; Surgical wound dehiscence; Abdomen; Surgery
5.  Comparison of the Effects of Different Negative Pressure Wound Therapy Modes—Continuous, Noncontinuous, and With Instillation—on Porcine Excisional Wounds 
Eplasty  2013;13:e51.
Objective: Negative pressure wound therapy (NPWT) can be delivered in continuous or noncontinuous modes, while NPWT with instillation (NPWTi) couples NPWT with automated delivery and removal of topical wound treatment solutions and suspensions. This porcine study compared granulation response of NPWTi (instillation foam dressing with saline) to NPWT (standard foam dressing) in continuous and noncontinuous modes. Methods: Full-thickness dorsal excisional wounds in pigs were treated with continuous NPWT, intermittent NPWT, dynamic (controlled variable) NPWT, and NPWTi with saline (n = 10 per group). Wound dimensions were determined from 3D images collected on days 0, 2, 5, and 7. On day 7, animals were euthanized and specimens were harvested for histopathological review. Results: Average granulation thickness was not statistically different among continuous (3.29 ± 0.33 mm), intermittent (3.03 ± 0.47 mm), and dynamic (3.40 ± 0.34 mm) NPWT wounds at day 7. Average granulation thickness of NPWTi wounds (4.75 ± 0.54 mm), however, was statistically greater (P < .05) by 44%, 57%, and 40%, respectively, than that of wounds treated with continuous, intermittent, and dynamic NPWT. Analysis of 3D images revealed a greater reduction in wound area and perimeter in NPWTi wounds compared to all NPWT wounds (P < .05). In addition, the average wound fill rate for NPWTi wounds was faster than that for continuous (40%; P < .05), intermittent (25%; P > .05), and dynamic (65%; P < .05) NPWT wounds. Conclusions: Although not confirmed in humans, these porcine data suggest that NPWTi with saline may stimulate a faster rate of wound granulation than NPWT in continuous and noncontinuous modes.
PMCID: PMC3791820  PMID: 24106564
dynamic NPWT; negative pressure wound therapy with instillation; preclinical model; variable NPWT; wound cleansing
6.  A rigid barrier between the heart and sternum protects the heart and lungs against rupture during negative pressure wound therapy 
Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier has been suggested to offer protection against this lethal complication, by preventing the heart from being drawn up and damaged by the sharp edges of the sternum. The aim of the present study was to investigate whether a rigid barrier protects the heart and lungs against injury during NPWT.
Sixteen pigs underwent median sternotomy followed by NPWT at -120 mmHg for 24 hours, in the absence (eight pigs) or presence (eight pigs) of a rigid plastic disc between the heart and the sternal edges. The macroscopic appearance of the heart and lungs was inspected after 12 and 24 hours of NPWT.
After 24 hours of NPWT at -120 mmHg the area of epicardial petechial bleeding was 11.90 ± 1.10 cm2 when no protective disc was used, and 1.15 ± 0.19 cm2 when using the disc (p < 0.001). Heart rupture was observed in three of the eight animals treated with NPWT without the disc. Lung rupture was observed in two of the animals, and lung contusion and emphysema were seen in all animals treated with NPWT without the rigid disc. No injury to the heart or lungs was observed in the group of animals treated with NPWT using the rigid disc.
Inserting a rigid barrier between the heart and the sternum edges offers protection against heart rupture and lung injury during NPWT.
PMCID: PMC3142210  PMID: 21740574
7.  Negative-pressure wound therapy for deep sternal wound infections reduces the rate of surgical interventions for early re-infections† 
To evaluate the outcome of treatment for deep sternal wound infection (DSWI) in a nationwide patient cohort, before and after the introduction of negative-pressure wound therapy (NPWT).
This was a population-based cohort of all patients treated for DSWI in Iceland out of 2446 open heart operations performed between 2000 and 2010. Length of hospital stay, survival and reoperations were compared in (i) 23 patients treated with open and/or closed irrigation before August 2005 (conventional treatment, CvT group) and in (ii) 20 patients treated after this time with NPWT as a first-line therapy (NPWT group).
The DSWI rate was 1.8% and did not change during the study period. Demographics were similar for both groups, except for peripheral arterial disease which was less common in the NPWT group. Coagulase-negative staphylococci were also more common (as the only pathogen identified) in the NPWT group (70% vs 30%, P = 0.01). The median length of hospital stay was 43 days in both groups and the sternum could be closed with delayed primary closure in all except 2 patients, one in each group. Eight patients in the CvT group required surgical revision for re-infections, including debridement and rewiring, when compared with 1 patient in the NPWT group (P = 0.02). Furthermore, 6 patients in the CvT group developed late chronic infections of the sternum requiring surgical revision, compared with one in the NPWT group (P = 0.10). The 30-day mortality was not significantly different between groups (4% vs 0%, P > 0.1) and the same was true for 1-year mortality (17% vs 0%, P = 0.11).
NPWT significantly reduces the risk of early re-infections in patients with DSWI. There was a lower rate of late chronic sternal infections and lower mortality in the NPWT group, but the difference was not statistically significant. We conclude that NPWT should be considered as a first-line treatment for most DSWIs.
PMCID: PMC3422957  PMID: 22691377
Deep sternal wound infection (DSWI); Mediastinitis; Cardiac surgery; Negative-pressure wound therapy; Outcome; Re-infection
8.  Negative pressure wound therapy management of the “open abdomen” following trauma: a prospective study and systematic review 
The use of Negative Pressure Wound Therapy (NPWT) for temporary abdominal closure of open abdomen (OA) wounds is widely accepted. Published outcomes vary according to the specific nature and the aetiology that resulted in an OA. The aim of this study was to evaluate the effectiveness of a new NPWT system specifically used OA resulting from abdominal trauma.
A prospective study on trauma patients requiring temporary abdominal closure (TAC) with grade 1or 2 OA was carried out. All patients were treated with NPWT (RENASYS AB Smith & Nephew) to achieve TAC. The primary outcome measure was time taken to achieve fascial closure and secondary outcomes were complications and mortality.
A total of 20 patients were included. Thirteen patients (65%) achieved fascial closure following a median treatment period of 3 days. Four patients (20%) died of causes unrelated to NPWT. Complications included fistula formation in one patient (5%) with spontaneous resolution during NPWT), bowel necrosis in a single patient (5%) and three cases of infection (15%). No fistulae were present at the end of NPWT.
This new NPWT kit is safe and effective and results in a high rate of fascial closure and low complication rates in the severely injured trauma patient.
PMCID: PMC3579683  PMID: 23305306
Negative Pressure Wound Therapy (NPWT); Grade 1 and 2 open abdomen; Abdominal trauma; Fascial closure
9.  Prospective Study Examining Clinical Outcomes Associated with a Negative Pressure Wound Therapy System and Barker’s Vacuum Packing Technique 
World Journal of Surgery  2013;37:2018-2030.
The open abdomen has become a common procedure in the management of complex abdominal problems and has improved patient survival. The method of temporary abdominal closure (TAC) may play a role in patient outcome.
A prospective, observational, open-label study was performed to evaluate two TAC techniques in surgical and trauma patients requiring open abdomen management: Barker’s vacuum-packing technique (BVPT) and the ABTheraTM open abdomen negative pressure therapy system (NPWT). Study endpoints were days to and rate of 30-day primary fascial closure (PFC) and 30-day all-cause mortality.
Altogether, 280 patients were enrolled from 20 study sites. Among them, 168 patients underwent at least 48 hours of consistent TAC therapy (111 NPWT, 57 BVPT). The two study groups were well matched demographically. Median days to PFC were 9 days for NPWT versus 12 days for BVPT (p = 0.12). The 30-day PFC rate was 69 % for NPWT and 51 % for BVPT (p = 0.03). The 30-day all-cause mortality was 14 % for NPWT and 30 % for BVPT (p = 0.01). Multivariate logistic regression analysis identified that patients treated with NPWT were significantly more likely to survive than the BVPT patients [odds ratio 3.17 (95 % confidence interval 1.22–8.26); p = 0.02] after controlling for age, severity of illness, and cumulative fluid administration.
Active NPWT is associated with significantly higher 30-day PFC rates and lower 30-day all-cause mortality among patients who require an open abdomen for at least 48 h during treatment for critical illness.
PMCID: PMC3742953  PMID: 23674252
10.  Negative pressure wound therapy for soft tissue injuries around the foot and ankle 
This study was performed to evaluate the results of negative pressure wound therapy (NPWT) in patients with open wounds in the foot and ankle region.
Materials and methods
Using a NPWT device, 16 patients were prospectively treated for soft tissue injuries around the foot and ankle. Mean patient age was 32.8 years (range, 3–67 years). All patients had suffered an acute trauma, due to a traffic accident, a fall, or a crush injury, and all had wounds with underlying tendon or bone exposure. Necrotic tissues were debrided before applying NPWT. Dressings were changed every 3 or 4 days and treatment was continued for 18.4 days on average (range, 11–29 days).
Exposed tendons and bone were successfully covered with healthy granulation tissue in all cases except one. The sizes of soft tissue defects reduced from 56.4 cm2 to 42.9 cm2 after NPWT (mean decrease of 24%). In 15 of the 16 cases, coverage with granulation tissue was achieved and followed by a skin graft. A free flap was needed to cover exposed bone and tendon in one case. No major complication occurred that was directly attributable to treatment. In terms of minor complications, two patients suffered scar contracture of grafted skin.
NPWT was found to facilitate the rapid formation of healthy granulation tissue on open wounds in the foot and ankle region, and thus, to shorten healing time and minimize secondary soft tissue defect coverage procedures.
PMCID: PMC2684535  PMID: 19426531
11.  Effects on heart pumping function when using foam and gauze for negative pressure wound therapy of sternotomy wounds 
Negative pressure wound therapy (NPWT) has remarkable effects on the healing of poststernotomy mediastinitis. Foam is presently the material of choice for NPWT in this indication. There is now increasing interest in using gauze, as this has proven successful in the treatment of peripheral wounds. It is important to determine the effects of NPWT using gauze on heart pumping function before it can be used for deep sternotomy wounds. The aim was to examine the effects of NPWT when using gauze and foam on the heart pumping function during the treatment of a sternotomy wound.
Eight pigs underwent median sternotomy followed by NPWT at -40, -70, -120 and -160 mmHg, using foam or gauze. The heart frequency, cardiac output, mean systemic arterial pressure, mean pulmonary artery pressure, central venous pressure and left atrial pressure were recorded.
Cardiac output was not affected by NPWT using gauze or foam. Heart frequency decreased during NPWT when using foam, but not gauze. Treatment with foam also lowered the central venous pressure and the left atrial pressure, while gauze had no such effects. Mean systemic arterial pressure, mean pulmonary artery pressure and systemic vascular resistance were not affected by NPWT. Similar haemodynamic effects were observed at all levels of negative pressure studied.
NPWT using foam results in decreased heart frequency and lower right and left atrial filling pressures. The use of gauze in NPWT did not affect the haemodynamic parameters studied. Gauze may thus provide an alternative to foam for NPWT of sternotomy wounds.
PMCID: PMC3031203  PMID: 21232105
12.  A pilot randomised controlled trial of negative pressure wound therapy to treat grade III/IV pressure ulcers [ISRCTN69032034] 
Trials  2012;13:119.
Negative pressure wound therapy (NPWT) is widely promoted as a treatment for full thickness wounds; however, there is a lack of high-quality research evidence regarding its clinical and cost effectiveness. A trial of NPWT for the treatment of grade III/IV pressure ulcers would be worthwhile but premature without assessing whether such a trial is feasible. The aim of this pilot randomised controlled trial was to assess the feasibility of conducting a future full trial of NPWT for the treatment of grade III and IV pressure ulcers and to pilot all aspects of the trial.
This was a two-centre (acute and community), pilot randomised controlled trial. Eligible participants were randomised to receive either NPWT or standard care (SC) (spun hydrocolloid, alginate or foam dressings). Outcome measures were time to healing of the reference pressure ulcer, recruitment rates, frequency of treatment visits, resources used and duration of follow-up.
Three hundred and twelve patients were screened for eligibility into this trial over a 12-month recruitment period and 12/312 participants (3.8%) were randomised: 6 to NPWT and 6 to SC. Only one reference pressure ulcer healed (NPWT group) during follow-up (time to healing 79 days). The mean number of treatment visits per week was 3.1 (NPWT) and 5.7 (SC); 6/6 NPWT and 1/6 SC participants withdrew from their allocated trial treatment. The mean duration of follow-up was 3.8 (NPWT) and 5.0 (SC) months.
This pilot trial yielded vital information for the planning of a future full study including projected recruitment rate, required duration of follow-up and extent of research nurse support required. Data were also used to inform the cost-effectiveness and value of information analyses, which were conducted alongside the pilot trial.
Trial registration
Current Controlled Trials ISRCTN69032034.
PMCID: PMC3533804  PMID: 22839453
Negative pressure wound therapy; Pressure ulcer; Pilot randomised controlled trial
13.  Assessment of Gauze-Based Negative Pressure Wound Therapy in the Split-Thickness Skin Graft Clinical Pathway—An Observational Study 
Eplasty  2011;11:e14.
Objectives: Negative pressure wound therapy (NPWT) is a useful therapy in the preparation of wounds prior to application of a split-thickness skin graft (STSG) both “pregraft” and “postgraft” on top of the STSG. Customarily, a foam-based NPWT has been used, but gauze-based therapy is finding an increasing use. Gauze is easy to apply and forgiving of complicated wound geometries so it can be an ideal material in this indication. The aim of this study was to quantitatively assess the clinical efficacy of gauze-based NPWT as an adjunctive therapy to STSG procedures. Methods: A prospective, noncomparative, multicenter evaluation was carried out to assess the performance of gauze-based NPWT. Twenty-one patients had NPWT applied prior to definitive closure by STSG or flap techniques (pregraft group). A further 21 patients underwent an STSG procedure and had gauze-based NPWT placed immediately on top of the STSG (postgraft group). Negative pressure was applied at −80 mm Hg. Results: In the pregraft group, NPWT was used for a median of 12 days. Improvement in quality of wound bed with decreased nonviable tissue (from 20% to 0% median wound area) and increased granulation tissue (from 20% to 90% median wound area) was observed. In the postgraft group, median duration of therapy was 5 days at which point median percentage skin graft-take was 96%. Conclusions: Gauze-based NPWT appears to be an effective addition to the care and management of wounds intended for definitive closure by STSG.
PMCID: PMC3060048  PMID: 21436890
14.  Does treatment of split-thickness skin grafts with negative-pressure wound therapy improve tissue markers of wound healing in a porcine experimental model? 
Negative-pressure wound therapy (NPWT) has been used for to treat wounds for more than 15 years and, more recently, has been used to secure split-thickness skin grafts. There are some data to support this use of NPWT, but the actual mechanism by which NPWT speeds healing or improves skin graft take is not entirely known. The purpose of this project was to assess whether NPWT improved angiogenesis, wound healing, or graft survival when compared with traditional bolster dressings securing split-thickness skin grafts in a porcine model.
We performed two split-thickness skin grafts on each of eight 30 kg Yorkshire pigs. We took graft biopsies on postoperative days 2, 4, 6, 8, and 10 and submitted the samples for immunohistochemical staining, as well as standard hematoxylin and eosin staining. We measured the degree of vascular ingrowth via immunohistochemical staining for von Willenbrand's factor to better identify blood vessel epithelium. We determined the mean cross-sectional area of blood vessels present for each representative specimen, and then compared the bolster and NPWT samples. We also assessed each graft for incorporation and survival at postoperative day 10.
Our analysis of the data revealed that there was no statistically significant difference in the degree of vascular ingrowth as measured by mean cross-sectional capillary area (p = 0.23). We did not note any difference in graft survival or apparent incorporation on a macroscopic level, although standard hematoxylin and eosin staining indicated that microscopically, there seemed to be better subjective graft incorporation in the NPWT samples and a nonsignificant trend toward improved graft survival in the NPWT group.
We were unable to demonstrate a significant difference in vessel ingrowth when comparing NPWT and traditional bolster methods for split-thickness skin graft fixation. More studies are needed to elucidate the manner by which NPWT exerts its effects and the true clinical magnitude of these effects.
Level of Evidence
Not applicable.
PMCID: PMC3698483  PMID: 22846954
Negative-pressure wound therapy; split thickness skin graft
15.  Disagreement in primary study selection between systematic reviews on negative pressure wound therapy 
Primary study selection between systematic reviews is inconsistent, and reviews on the same topic may reach different conclusions. Our main objective was to compare systematic reviews on negative pressure wound therapy (NPWT) regarding their agreement in primary study selection.
This retrospective analysis was conducted within the framework of a systematic review (a full review and a subsequent rapid report) on NPWT prepared by the Institute for Quality and Efficiency in Health Care (IQWiG).
For the IQWiG review and rapid report, 4 bibliographic databases (MEDLINE, EMBASE, The Cochrane Library, and CINAHL) were searched to identify systematic reviews and primary studies on NPWT versus conventional wound therapy in patients with acute or chronic wounds. All databases were searched from inception to December 2006.
For the present analysis, reviews on NPWT were classified as eligible systematic reviews if multiple sources were systematically searched and the search strategy was documented. To ensure comparability between reviews, only reviews published in or after December 2004 and only studies published before June 2004 were considered.
Eligible reviews were compared in respect of the methodology applied and the selection of primary studies.
A total of 5 systematic reviews (including the IQWiG review) and 16 primary studies were analysed. The reviews included between 4 and 13 primary studies published before June 2004. Two reviews considered only randomised controlled trials (RCTs). Three reviews considered both RCTs and non-RCTs. The overall agreement in study selection between reviews was 96% for RCTs (24 of 25 options) and 57% for non-RCTs (12 of 21 options). Due to considerable disagreement in the citation and selection of non-RCTs, we contacted the review authors for clarification (this was not initially planned); all authors or institutions responded. According to published information and the additional information provided, most differences between reviews arose from variations in inclusion criteria or inter-author study classification, as well as from different reporting styles (citation or non-citation) for excluded studies.
The citation and selection of primary studies differ between systematic reviews on NPWT, particularly with regard to non-RCTs. Uniform methodological and reporting standards need to be applied to ensure comparability between reviews as well as the validity of their conclusions.
PMCID: PMC2496910  PMID: 18582373
16.  Negative pressure wound therapy: Potential publication bias caused by lack of access to unpublished study results data 
Negative pressure wound therapy (NPWT) is widely applied, although the evidence base is weak. Previous reviews on medical interventions have shown that conclusions based on published data alone may no longer hold after consideration of unpublished data. The main objective of this study was to identify unpublished randomised controlled trials (RCTs) on NPWT within the framework of a systematic review.
RCTs comparing NPWT with conventional wound therapy were identified using MEDLINE, EMBASE, CINAHL and The Cochrane Library. Every database was searched from inception to May 2005. The search was updated in December 2006. Reference lists of original articles and systematic reviews, as well as congress proceedings and online trial registers, were screened for clues to unpublished RCTs. Manufacturers of NPWT devices and authors of conference abstracts were contacted and asked to provide study information. Trials were considered nonrandomised if concealment of allocation to treatment groups was classified as "inadequate". The study status was classified as "completed", "discontinued", "ongoing" or "unclear". The publication status of completed or discontinued RCTs was classified as "published" if a full-text paper on final study results (completed trials) or interim results (discontinued trials) was available, and "unpublished" if this was not the case. The type of sponsorship was also noted for all trials.
A total of 28 RCTs referring to at least 2755 planned or analysed patients met the inclusion criteria: 13 RCTs had been completed, 6 had been discontinued, 6 were ongoing, and the status of 3 RCTs was unclear. Full-text papers were available on 30% of patients in the 19 completed or discontinued RCTs (495 analysed patients in 10 published RCTs vs. 1154 planned patients in 9 unpublished RCTs). Most information about conference abstracts and unpublished study information referring to trials that were unpublished at the time these documents were generated was obtained from the manufacturer Kinetic Concepts Inc. (KCI) (19 RCTs), followed by The Cochrane Library (18) and a systematic review (15). We were able to obtain some information on the methods of unpublished RCTs, but results data were either not available or requests for results data were not answered; the results of unpublished RCTs could therefore not be considered in the review. One manufacturer, KCI, sponsored the majority of RCTs (19/28; 68%). The sponsorship of the remaining trials was unclear.
Multi-source comprehensive searches identify unpublished RCTs. However, lack of access to unpublished study results data raises doubts about the completeness of the evidence base on NPWT.
PMCID: PMC2291064  PMID: 18267008
17.  Wound contraction and macro-deformation during negative pressure therapy of sternotomy wounds 
Negative pressure wound therapy (NPWT) is believed to initiate granulation tissue formation via macro-deformation of the wound edge. However, only few studies have been performed to evaluate this hypothesis. The present study was performed to investigate the effects of NPWT on wound contraction and wound edge tissue deformation.
Six pigs underwent median sternotomy followed by magnetic resonance imaging in the transverse plane through the thorax and sternotomy wound during NPWT at 0, -75, -125 and -175 mmHg. The lateral width of the wound and anterior-posterior thickness of the wound edge was measured in the images.
The sternotomy wound decreased in size following NPWT. The lateral width of the wound, at the level of the sternum bone, decreased from 39 ± 7 mm to 30 ± 6 mm at -125 mmHg (p = 0.0027). The greatest decrease in wound width occurred when switching from 0 to -75 mmHg. The level of negative pressure did not affect wound contraction (sternum bone: 32 ± 6 mm at -75 mmHg and 29 ± 6 mm at -175 mmHg, p = 0.0897). The decrease in lateral wound width during NPWT was greater in subcutaneous tissue (14 ± 2 mm) than in sternum bone (9 ± 2 mm), resulting in a ratio of 1.7 ± 0.3 (p = 0.0423), suggesting macro-deformation of the tissue. The anterior-posterior thicknesses of the soft tissue, at 0.5 and 2.5 cm laterally from the wound edge, were not affected by negative pressure.
NPWT contracts the wound and causes macro-deformation of the wound edge tissue. This shearing force in the tissue and at the wound-foam interface may be one of the mechanisms by which negative pressure delivery promotes granulation tissue formation and wound healing.
PMCID: PMC2958889  PMID: 20920290
18.  Negative-pressure wound therapy induces endothelial progenitor cell mobilization in diabetic patients with foot infection or skin defects 
Non healing chronic wounds are difficult to treat in patients with diabetes and can result in severe medical problems for these patients and for society. Negative-pressure wound therapy (NPWT) has been adopted to treat intractable chronic wounds and has been reported to be effective. However, the mechanisms underlying the effects of this treatment have not been elucidated. To assess the vasculogenic effect of NPWT, we evaluated the systemic mobilization of endothelial progenitor cells (EPCs) during NPWT. Twenty-two of 29 consecutive patients who presented at the clinic of Seoul National Universty Hospital between December 2009 and November 2010 who underwent NPWT for diabetic foot infections or skin ulcers were included in this study. Peripheral blood samples were taken before NPWT (pre-NPWT) and 7–14 days after the initiation of NPWT (during-NPWT). Fluorescence-activated cell sorting (FACS) analysis showed that the number of cells in EPC-enriched fractions increased after NPWT, and the numbers of EPC colony forming units (CFUs) significantly increased during NPWT. We believe that NPWT is useful for treating patients with diabetic foot infections and skin ulcers, especially when these conditions are accompanied by peripheral arterial insufficiency. The systemic mobilization of EPCs during NPWT may be a mechanism for healing intractable wounds in diabetic patients with foot infections or skin defects via the formation of increased granulation tissue with numerous small blood vessels.
PMCID: PMC3849576  PMID: 24232261
diabetic foot; endothelial progenitor cell; negative-pressure wound therapy
19.  Sternum wound contraction and distension during negative pressure wound therapy when using a rigid disc to prevent heart and lung rupture 
There are increasing reports of deaths and serious complications associated with the use of negative pressure wound therapy (NPWT), of which right ventricular heart rupture is the most devastating. The use of a rigid barrier has been suggested to offer protection against this lethal complication by preventing the heart from being drawn up against the sharp edges of the sternum. The aim of the present study was to determine whether a rigid barrier can be safely inserted over the heart with regard to the sternum wound edge movement.
Sternotomy wounds were created in eight pigs. The wounds were treated with NPWT at -40, -70, -120 and -170 mmHg in the presence and absence of a rigid barrier between the heart and the edges of the sternum. Wound contraction upon NPWT application, and wound distension under mechanical traction to draw apart the edges of the sternotomy were evaluated.
Wound contraction resulting from NPWT was similar with and without the rigid barrier. When mechanical traction was applied to a NPWT treated sternum wound, the sternal edges were pulled apart. Wound distension upon traction was similar in the presence and absence of a the rigid barrier during NPWT.
A rigid barrier can safely be inserted between the heart and the edges of the sternum to protect the heart and lungs from rupture during NPWT. The sternum wound edge is stabilized equally well with as without the rigid barrier during NPWT.
PMCID: PMC3073896  PMID: 21450095
20.  Negative pressure wound therapy to prevent seromas and treat surgical incisions after total hip arthroplasty 
International Orthopaedics  2011;36(4):719-722.
The purpose of this study was to evaluate the use of negative pressure wound therapy (NPWT) to improve wound healing after total hip arthroplasty (THA) and its influence on the development of postoperative seromas in the wound area.
The study is a prospective randomised evaluation of NPWT in patients with large surgical wounds after THA, randomising patients to either a standard dressing (group A) or a NPWT (group B) over the wound area. The wound area was examined with ultrasound to measure the postoperative seromas in both groups on the fifth and tenth postoperative days.
There were 19 patients randomised in this study. Ten days after surgery, group A (ten patients, 70.5 ± 11.01 years of age) developed seromas with an average size of 5.08 ml and group B (nine patients, 66.22 ± 17.83 years of age) 1.97 ml. The difference was significant (p = 0.021).
NPWT has been used on many different types of traumatic and non traumatic wounds. This prospective, randomised study has demonstrated decreased development of postoperative seromas in the wound and improved wound healing.
PMCID: PMC3311811  PMID: 21761149
21.  Negative Pressure Wound Therapy Literature Review of Efficacy, Cost Effectiveness, and Impact on Patients' Quality of Life in Chronic Wound Management and Its Implementation in the United Kingdom 
Plastic Surgery International  2012;2012:374398.
This is a paper reviewing the National Health Service (NHS) agenda in relation to the use of Negative Pressure Wound Therapy (NPWT) in chronic wound management and assesses the evidence behind it, its cost effectiveness and the outcome it has on patients' satisfaction and life style. Multiple studies over the last 10 years looking at clinical efficacy of NPWT with its cost effectiveness and the implementation of this service in the UK were reviewed. NPWT has showed a reasonable body of evidence to support its usage in chronic wounds with potential positive outcomes on finance and patients' satisfaction. However, the NHS system shows significant variations in the availability and implementation of this useful tool, depending on care providers and resources availabilities. The paper concluded that the NPWT can be a useful source of cutting down costs of chronic wound managements and saving money by its effect on expediting wound healing, which can address a part of the financial crises facing the NHS, however, has to be considered according to specific case needs. There should also be a national standard for the availability and indication of this tool to assure equal opportunities for different patients in different areas in the country.
PMCID: PMC3369418  PMID: 22701169
22.  Wound Chemotherapy by the Use of Negative Pressure Wound Therapy and Infusion 
Eplasty  2010;10:e9.
Introduction: Although the use of negative pressure wound therapy (NPWT) is broadly efficacious, it may foster some potentially adverse complications. This is particularly true in patients with diabetes who have a wound colonized with aerobic organisms. Traditional antiseptics have been proven useful to combat such bacteria but require removal of some NPWT devices to be effective. Methods: In this article, we describe a method of “wound chemotherapy” by combining NPWT and a continuous infusion of Dakins' 0.5% solution either as a standardized technique in one device (ITI Sved) or as a modification of standard technique in another (KCI VAC) NPWT device. The twin goals of both techniques are to effectively reduce bacterial burden and to promote progressive wound healing. Results: We present several representative case examples of our provisional experience with continuous streaming therapy through 2 foam-based negative pressure devices. Discussion: Wound chemotherapy was successfully applied to patients with diabetes, without adverse reactions, complications, or recolonization during the course of treatment. We believe this to be a promising method to derive the benefits of NPWT without the frequent adverse sequela of wound colonization.
PMCID: PMC2806786  PMID: 20090841
23.  SNaP® Wound Care System: Ultraportable Mechanically Powered Negative Pressure Wound Therapy 
Advances in Wound Care  2012;1(1):41-43.
Negative pressure wound therapy (NPWT) is a well-accepted modality for treatment of difficult wounds, but has traditionally required a bulky electrically powered pump that was difficult to procure and use for both caregivers and patients. Often times, treatment of refractory smaller-sized wounds was impractical even though they may benefit from NPWT.
Spiracur (Sunnyvale, CA) has developed a simple, easy-to-use, single-use, off-the-shelf, mechanically powered NPWT device that weighs <3 ounces. This device allows for the practical treatment of smaller-sized wounds with NPWT designed specifically for the ambulatory patient being treated at home.
New Technology
The Smart Negative Pressure (SNaP®) Wound Care System is a novel light-weight NPWT device that does not require an electrically powered pump. Instead, the SNaP system utilizes specialized springs to generate a preset (−75, −100, and −125 mmHg) continuous subatmospheric pressure level to the wound bed. This technology has demonstrated similar efficacy and increased usability for both clinicians and patients when compared with electrically powered NPWT devices.
Indications for Use
Chronic, acute, traumatic, subacute, and dehisced wounds, partial-thickness burns, ulcers (such as diabetic or pressure), and surgically closed incisions and flaps.
Wounds with excess necrotic tissue, active infection, fistulas, exposed vital structures, untreated osteomyelitis, and that are highly exudative. The SNaP system was not designed for wounds that exceed the size of the dressing in surface area or have exudate levels greater than capacity of the cartridge.
PMCID: PMC3839001  PMID: 24527277
24.  The SNaP™ Wound Care System: A Case Series Using a Novel Ultraportable Negative Pressure Wound Therapy Device for the Treatment of Diabetic Lower Extremity Wounds 
Although there is significant evidence supporting the use of negative pressure wound therapy (NPWT) for the treatment of lower extremity diabetic ulcers, currently available electrically powered NPWT systems are not ideally suited for treating smaller diabetic foot ulcers. The Smart Negative Pressure (SNaP™) Wound Care System is a novel, ultraportable device that delivers NPWT without the use of an electrically powered pump. It was specifically designed to meet the wound care needs of patients with diabetes. The SNaP System is compact, silent, mobile, easy-to-use, and available off-the-shelf. It is fully disposable and may offer other important benefits over electrically powered systems to both the clinician and patient. We review the evidence for use of NPWT for the treatment of diabetic wounds and discuss the potential benefits of this new NPWT technology for patients with diabetes. We also present a case series of four difficult lower extremity diabetic ulcers that were successfully treated with the SNaP System. This study suggests that the SNaP System may be a useful addition to the armamentarium of the diabetic wound care clinician.
PMCID: PMC2909512  PMID: 20663444
Apligraf®; chronic ulcers; diabetic foot ulcers; NPWT; negative pressure wound therapy; SNaP™ System; topical negative pressure; ultraportable negative pressure wound therapy; wound VAC®
25.  Use of Bacteria- and Fungus-Binding Mesh in Negative Pressure Wound Therapy Provides Significant Granulation Tissue Without Tissue Ingrowth 
Eplasty  2014;14:e3.
Objective: Bacteria- and fungus-binding mesh traps and inactivates bacteria and fungus, which makes it interesting, alternative, and wound filler for negative pressure wound therapy (NPWT). The aim of this study was to compare pathogen-binding mesh, black foam, and gauze in NPWT with regard to granulation tissue formation and ingrowth of wound bed tissue in the wound filler. Methods: Wounds on the backs of 8 pigs underwent 72 hours of NPWT using pathogen-binding mesh, foam, or gauze. Microdeformation of the wound bed and granulation tissue formation and the force required to remove the wound fillers was studied. Results: Pathogen-binding mesh produced more granulation tissue, leukocyte infiltration, and tissue disorganization in the wound bed than gauze, but less than foam. All 3 wound fillers caused microdeformation of the wound bed surface. Little force was required to remove pathogen-binding mesh and gauze, while considerable force was needed to remove foam. This is the result of tissue growth into the foam, but not into pathogen-binding mesh or gauze, as shown by examination of biopsy sections from the wound bed. Conclusions: This study shows that using pathogen-binding mesh as a wound filler for NPWT leads to a significant amount of granulation tissue in the wound bed, more than that with gauze, but eliminates the problems of ingrowth of the wound bed into the wound filler. Pathogen-binding mesh is thus an interesting wound filler in NPWT.
PMCID: PMC3899807  PMID: 24501617
blood flow; experimental surgery; negative pressure wound therapy; wound contraction; wound dressing; wound healing

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