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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.  Negative Pressure Wound Therapy 
Executive Summary
This review was conducted to assess the effectiveness of negative pressure wound therapy.
Clinical Need: Target Population and Condition
Many wounds are difficult to heal, despite medical and nursing care. They may result from complications of an underlying disease, like diabetes; or from surgery, constant pressure, trauma, or burns. Chronic wounds are more often found in elderly people and in those with immunologic or chronic diseases. Chronic wounds may lead to impaired quality of life and functioning, to amputation, or even to death.
The prevalence of chronic ulcers is difficult to ascertain. It varies by condition and complications due to the condition that caused the ulcer. There are, however, some data on condition-specific prevalence rates; for example, of patients with diabetes, 15% are thought to have foot ulcers at some time during their lives. The approximate community care cost of treating leg ulcers in Canada, without reference to cause, has been estimated at upward of $100 million per year.
Surgically created wounds can also become chronic, especially if they become infected. For example, the reported incidence of sternal wound infections after median sternotomy is 1% to 5%. Abdominal surgery also creates large open wounds. Because it is sometimes necessary to leave these wounds open and allow them to heal on their own (secondary intention), some may become infected and be difficult to heal.
Yet, little is known about the wound healing process, and this makes treating wounds challenging. Many types of interventions are used to treat wounds.
Current best practice for the treatment of ulcers and other chronic wounds includes debridement (the removal of dead or contaminated tissue), which can be surgical, mechanical, or chemical; bacterial balance; and moisture balance. Treating the cause, ensuring good nutrition, and preventing primary infection also help wounds to heal. Saline or wet-to-moist dressings are reported as traditional or conventional therapy in the literature, although they typically are not the first line of treatment in Ontario. Modern moist interactive dressings are foams, calcium alginates, hydrogels, hydrocolloids, and films. Topical antibacterial agents—antiseptics, topical antibiotics, and newer antimicrobial dressings—are used to treat infection.
The Technology Being Reviewed
Negative pressure wound therapy is not a new concept in wound therapy. It is also called subatmospheric pressure therapy, vacuum sealing, vacuum pack therapy, and sealing aspirative therapy.
The aim of the procedure is to use negative pressure to create suction, which drains the wound of exudate (i.e., fluid, cells, and cellular waste that has escaped from blood vessels and seeped into tissue) and influences the shape and growth of the surface tissues in a way that helps healing. During the procedure, a piece of foam is placed over the wound, and a drain tube is placed over the foam. A large piece of transparent tape is placed over the whole area, including the healthy tissue, to secure the foam and drain the wound. The tube is connected to a vacuum source, and fluid is drawn from the wound through the foam into a disposable canister. Thus, the entire wound area is subjected to negative pressure. The device can be programmed to provide varying degrees of pressure either continuously or intermittently. It has an alarm to alert the provider or patient if the pressure seal breaks or the canister is full.
Negative pressure wound therapy may be used for patients with chronic and acute wounds; subacute wounds (dehisced incisions); chronic, diabetic wounds or pressure ulcers; meshed grafts (before and after); or flaps. It should not be used for patients with fistulae to organs/body cavities, necrotic tissue that has not been debrided, untreated osteomyelitis, wound malignancy, wounds that require hemostasis, or for patients who are taking anticoagulants.
Review Strategy
The inclusion criteria were as follows:
Randomized controlled trial (RCT) with a sample size of 20 or more
Human study
Published in English
Summary of Findings
Seven international health technology assessments on NPWT were identified. Included in this list of health technology assessments is the original health technology review on NPWT by the Medical Advisory Secretariat from 2004. The Medical Advisory Secretariat found that the health technology assessments consistently reported that NPWT may be useful for healing various types of wounds, but that its effectiveness could not be empirically quantified because the studies were poorly done, the patient populations and outcome measures could not be compared, and the sample sizes were small.
Six RCTs were identified that compared NPWT to standard care. Five of the 6 studies were of low or very low quality according to Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. The low and very low quality RCTs were flawed owing to small sample sizes, inconsistent reporting of results, and patients lost to follow-up. The highest quality study, which forms the basis of this health technology policy assessment, found that:
There was not a statistically significant difference (≥ 20%) between NPWT and standard care in the rate of complete wound closure in patients who had complete wound closure but did not undergo surgical wound closure (P = .15).
The authors of this study did not report the length of time to complete wound closure between NPWT and standard care in patients who had complete wound closure but who did not undergo surgical wound closure
There was no statistically significant difference (≥ 20%) in the rate of secondary amputations between the patients that received NPWT and those that had standard care (P = .06)
There may be an increased risk of wound infection in patients that receive NPWT compared with those that receive standard care.
Based on the evidence to date, the clinical effectiveness of NPWT to heal wounds is unclear. Furthermore, saline dressings are not standard practice in Ontario, thereby rendering the literature base irrelevant in an Ontario context. Nonetheless, despite the lack of methodologically sound studies, NPWT has diffused across Ontario.
Discussions with Ontario clinical experts have highlighted some deficiencies in the current approach to wound management, especially in the community. Because NPWT is readily available, easy to administer, and may save costs, compared with multiple daily conventional dressing changes, it may be used inappropriately. The discussion group highlighted the need to put in place a coordinated, multidisciplinary strategy for wound care in Ontario to ensure the best, continuous care of patients.
PMCID: PMC3379164  PMID: 23074484
3.  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
4.  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
5.  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
6.  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
7.  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(9):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
8.  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
9.  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
10.  Influence of Negative-Pressure Wound Therapy on Tissue Oxygenation of the Foot 
Archives of Plastic Surgery  2014;41(6):668-672.
Negative-pressure wound therapy (NPWT) is believed to accelerate wound healing by altering wound microvascular blood flow. Although many studies using laser Doppler have found that NPWT increases perfusion, recent work using other modalities has demonstrated that perfusion is reduced. The purpose of this study was to investigate the influence of NPWT on tissue oxygenation of the foot, which is the most sensitive region of the body to ischemia.
Transcutaneous partial pressure of oxygen (TcpO2) was used to determine perfusion beneath NPWT dressings of 10 healthy feet. The sensor was placed on the tarso-metatarsal area of the foot and the NPWT dressing was placed above the sensor. TcpO2 was measured until it reached a steady plateau state. The readings obtained at the suction-on period were compared with the initial baseline (pre-suction) readings.
TcpO2 decreased significantly immediately after applying NPWT, but gradually increased over time until reaching a steady plateau state. The decrease in TcpO2 from baseline to the steady state was 2.9 to 13.9 mm Hg (mean, 9.3±3.6 mm Hg; 13.5±5.8%; P<0.01). All feet reached a plateau within 20 to 65 minutes after suction was applied.
NPWT significantly decrease tissue oxygenation of the foot by 2.9 to 13.9 mm Hg. NPWT should be used with caution on feet that do not have adequate tissue oxygenation for wound healing.
PMCID: PMC4228208  PMID: 25396178
Negative-pressure wound therapy; Oxygen partial pressure determination, Transcutaneous; Foot
11.  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
12.  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
13.  Effects of Negative Pressure Wound Therapy on Healing of Free Full-Thickness Skin Grafts in Dogs 
Veterinary surgery : VS  2013;42(5):511-522.
To compare healing of free, full-thickness, meshed skin grafts under negative pressure wound therapy (NPWT) with bolster dressings in dogs.
Study design
Randomized, controlled experimental study, paired design.
Dogs (n =5)
Full-thickness skin wounds (4 cm ×1.5cm) were created bilaterally on the antebrachia of 5 dogs (n = 10). Excised skin was grafted to the contralateral limb. Grafts were randomized to NPWT or bolster dressings (control; CON). NPWT was applied continuously for 7 days. Grafts were evaluated on days 2, 4, 7, 10, 14 and 17, biopsied on days 0, 4, 7, and 14, and had microbial culture on day 7. Outcome variables were: time to first appearance of granulation tissue, percent graft necrosis, and percent open mesh. Significance was set at P<.05. Histologic findings, culture results, and graft appearance were reported.
Granulation tissue appeared earlier in the NPWT grafts compared with CON grafts. Percent graft necrosis and remaining open mesh area were both greater in CON grafts compared with NPWT grafts at most time points. Histologic results showed no significant difference in all variables measured, and all cultures were negative.
Variables of graft acceptance were superior when NPWT was used in the first week post-grafting. Fibroplasia was enhanced, open meshes closed more rapidly and less graft necrosis occurred with NPWT application. More preclinical studies are required to evaluate histologic differences.
PMCID: PMC3713772  PMID: 23550662
14.  Biological Effects of a Disposable, Canisterless Negative Pressure Wound Therapy System 
Eplasty  2014;14:e15.
Objective: Recent developments of negative pressure wound therapy (NPWT) systems have focused on making pumps smaller, lighter, and more portable. The recently introduced PICO system manages wound fluid through a highly breathable film within the dressing, thereby negating the need for a canister, which allows greater mobility and patient concordance. The aim of this study is to compare the biological effects of this system compared to a traditional NPWT system. Methods: Laboratory tests were carried out to demonstrate the fluid handling properties of the PICO™ system. Porcine full thickness defect wounds and sutured incisional wounds were used to compare the biological effects. Wounds were treated with PICO dressings or traditional NPWT dressings and connected to either a PICO device or a traditional NPWT device. Results: The PICO dressing manages exudate predominantly through evaporative loss (up to 85% of all fluid entering the dressing). Both traditional NPWT and the PICO system maintained therapeutic levels of negative pressure in all wounds. Both NPWT systems produced similar effects on wound edge contraction and microvascular blood flow in defect wounds. No significant changes in blood flow or wound contraction were noted in incision wounds for any NPWT combinations tested. Conclusions: The disposable, canisterless PICO NPWT system functions in the same manner as the traditional NPWT systems with regard to fluid handling, pressure transmission to the wound bed, tissue contraction, and changes in blood flow.
PMCID: PMC3977592  PMID: 24741386
Blood flow; dressing; wound; NPWT; vacuum
15.  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
16.  Effects of Negative Pressure Wound Therapy on Mesenchymal Stem Cells Proliferation and Osteogenic Differentiation in a Fibrin Matrix 
PLoS ONE  2014;9(9):e107339.
Vacuum-assisted closure (VAC) negative pressure wound therapy (NPWT) has been proven to be an effective therapeutic method for the treatment of recalcitrant wounds. However, its role in bone healing remains to be unclear. Here, we investigated the effects of NPWT on rat periosteum-derived mesenchymal stem cells (P-MSCs) proliferation and osteoblastic differentiation in a 3D fibrin matrix. P-MSCs underwent primary culture for three passages before being used to construct cell clots. The fibrin clots were incubated with NPWT under continuous suction at −125 mmHg in a subatmospheric perfusion bioreactor. Clots exposed to atmospheric pressure served as the static control. Compared to the control group, cell proliferation significantly increased in NPWT group after incubation for 3 days. There was no statistical difference in apoptosis rate between two groups. The ALP activity and mineralization of P-MSCs all increased under continuous suction. The expressions of collagen type 1 and transcription factor Cbfa-1 were higher at the 1-, 3-, and 7-day timepoints and the expressions of osteocalcin and integrin β5 were higher at the 3-, and 7-day timepoints in the NPWT group. These results indicate that a short time treatment with NPWT, applied with continuous suction at −125 mmHg, can enhance cellular proliferation of P-MSCs and induce the differentiation toward an osteogenic phenotype. The mechanotransduction molecule integrin β5 was found to be highly expressed after NPWT treatment, which indicates that NPWT may play a positive role in fracture healing through enhance bone formation and decrease bone resorption.
PMCID: PMC4162584  PMID: 25216182
17.  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
18.  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
19.  The Duration of Negative Pressure Wound Therapy Can Be Reduced Using the HeartShield Device in Patients With Deep Sternal Wound Infection 
Eplasty  2014;14:e16.
Background: Heart rupture resulting in lethal bleeding is a devastating complication associated with negative pressure wound therapy (NPWT) in patients with deep sternal wound infection (DSWI). We have previously reported that the use of a protective HeartShield device in combination with NPWT decreases the risk of damage to the heart. This article presents a retrospective analysis of NPWT duration with and without the HeartShield device. Subjects and patients: The study included 6 patients treated with the HeartShield device in combination with NPWT and 6 patients treated with conventional NPWT during the same time period. The duration of active treatment time was measured. Results: The median duration of NPWT was 8 days (range: 6-14 days) in the HeartShield device NPWT group and 14 days in the conventional group (range: 10-18 days). The difference was statistically significant (P < .05). Conclusions: It appears that the treatment of patients with DSWI with the HeartShield device reduces the duration of NPWT.
PMCID: PMC3977590  PMID: 24741387
Wound; heart; sternotomy; NPWT; vacuum
20.  Negative Pressure Wound Therapy Is Associated With Resolution of Incisional Drainage in Most Wounds After Hip Arthroplasty 
Persistent wound drainage after hip arthroplasty is a risk factor for periprosthetic infection. Negative pressure wound therapy (NPWT) has been used in other fields for wound management although it is unclear whether the technique is appropriate for total hip arthroplasty.
We determined (1) the rate of wound complications related to use of NPWT for persistent incisional drainage after hip arthroplasty; (2) the rate of resolution of incisional drainage using this modality; and (3) risk factors for failure of NPWT for this indication.
In a pilot study we identified 109 patients in whom NPWT was used after hip arthroplasty for treating postoperative incisional drainage between April 2006 and April 2010. On average, the NPWT was placed on postoperative Day 3 to 4 (range, 2–9 days) and applied for 2 days (range, 1–10 days). We then determined predictors of subsequent surgery. Patients were followed until failure or a minimum of 1 year (average, 29 months; range, 1–62 months).
Eighty-three patients (76%) had no further surgery and 26 patients (24%) had subsequent surgery: 11 had superficial irrigation and débridement (I&D), 12 had deep I&D with none requiring further surgery, and three ultimately had component removal. Predictors of subsequent surgery included international normalized ratio level greater than 2, greater than one prior hip surgery, and device application greater than 48 hours. There were no wound-related complications associated with NPWT.
The majority of our patients had cessation of wound drainage with NPWT.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC3773159  PMID: 23539123
21.  Extended negative pressure wound therapy-assisted dermatotraction for the closure of large open fasciotomy wounds in necrotizing fasciitis patients 
Necrotizing fasciitis (NF) is a rapid progressive infection of the subcutaneous tissue or fascia and may result in large open wounds. The surgical options to cover these wounds are often limited by the patient condition and result in suboptimal functional and cosmetic wound coverage. Dermatotraction can restore the function and appearance of the fasciotomy wound and is less invasive in patients with comorbidities. However, dermatotraction for scarred, stiff NF fasciotomy wounds is often ineffective, resulting in skin necrosis. The authors use extended negative pressure wound therapy (NPWT) as an assist in dermatotraction to close open NF fasciotomy wounds. The authors present the clinical results, followed by a discussion of the clinical basis of extended NPWT-assisted dermatotraction.
A retrospective case series of eight patients with NF who underwent open fasciotomy was approved for the study. After serial wound preparation, dermatotraction was applied in a shoelace manner using elastic vessel loops. Next, the extended NPWT was applied over the wound. The sponge was three times wider than the wound width, and the transparent covering drape almost encircled the anatomical wound area. The negative pressure of the NPWT was set at a continuous 100 mmHg by suction barometer. The clinical outcome was assessed based on wound area reduction after treatment and by the achievement of direct wound closure.
After the first set of extended NPWT-assisted dermatotraction procedures, the mean wound area was significantly decreased (658.12 cm2 to 29.37 cm2; p = 0.002), as five out of eight patients achieved direct wound closure. One patient with a chest wall defect underwent latissimus dorsi musculocutaneous flap coverage, with primary closure of the donor site. Two Fournier’s gangrene patients underwent multiple sets of treatment and finally achieved secondary wound closure with skin grafts. The patients were followed up for 18.3 months on average and showed satisfactory results without wound recurrence.
Extended NPWT-assisted dermatotraction advances scarred, stiff fasciotomy wound margins synergistically in NF and allows direct closure of the wound without complications. This method can be another good treatment option for the NF patient with large open wounds whose general condition is unsuitable for extensive reconstructive surgery.
PMCID: PMC3996171  PMID: 24731449
Necrotizing fasciitis; Negative pressure wound therapy; Dermatotraction; Fournier’s gangrene; Fasciotomy
22.  Application of the Single Use Negative Pressure Wound Therapy Device (PICO) on a Heterogeneous Group of Surgical and Traumatic Wounds 
Eplasty  2014;14:e20.
Objectives: Traumatic wounds and surgery inherently have their complications. Localized infections, wound dehiscence, and excessive wound leakage can be devastating to the patient with a prolonged recovery, but it is also costly to the hospital with an increased length of stay, extra workload, and dressing changes. The single use PICO (Smith and Nephew Healthcare, Hull, United Kingdom) negative pressure wound therapy (NPWT) dressing has revolutionized our management of various acute, chronic, and high output wounds. It requires fewer dressing changes than conventional practice, is used in the outpatient setting, and is a necessary adjuvant therapy to hasten wound healing. Aims: To observe the efficacy of the PICO vacuum-assisted healing within a cost improvement programme. Settings: Plastic surgery department, Royal London Hospital. Materials and Methods: Twenty-one patients with a diversity of postoperative or posttraumatic wounds were considered suitable for PICO application and treated totally on an outpatient basis once the PICO dressing was applied. All wounds were then subjected to continued PICO dressings until healed. Results: All patients tolerated the PICO well with no dressing failure or failure to comply. The number of dressings per patient ranged from 1 to 7. The cost per patient of treatment ranged from £120 to £1578. Estimated cost of all PICO dressing for 21 patients including plastic surgery dressing clinic appointments = £13,345. Median length of treatment to healing (days) = 16; standard deviation = 9.5. Eight patients would have had an inpatient bed stay with conventional therapy, total 24 bed days saved at Bartshealth @£325 per day. Conclusions: The outpatient application of a disposable NPWT can benefit a wide range of clinical wounds that optimizes patient care, promotes rapid wound healing, and importantly helps manage costs.
PMCID: PMC4006427  PMID: 24917894
plastic surgery; wound management; negative pressure wound dressing; single use device; early patient discharge
23.  Use of an Acellular Regenerative Tissue Matrix Over Chronic Wounds 
Eplasty  2013;13:e61.
Objectives: Bioengineered skin grafts, including acellular dermal matrices, may be effective in treating lower extremity and trunk wounds that are not responsive to traditional wound management. Acellular dermal wound matrix is derived from human acellular dermal wound matrix (HADWM) tissue and provides a scaffold that supports cellular repopulation and revascularization. The major structural components of the dermis are retained during processing, and a single application has been shown to help achieve wound closure. Methods: This patient case series examined the use of HADWM on lower extremity and trunk wounds in 11 patients (6 male and 5 female) with a mean age of 55 years (range: 31–83 years). Wounds were debrided 1 to 2 times, followed by placement of HADWM (range: 4–330 cm2) on wounds that varied from the dorsal surface of the foot, lower abdomen, and lower extremity to the Achilles flap. A nonadherent layer in conjunction with bacitracin was placed over HADWM. Negative pressure wound therapy (NPWT) was placed over the HADWM and initiated continuously at −125 mm Hg for 1 to 2 weeks. After the application of NPWT, HADWM was covered with various gauze dressings using mineral oil. Results: All patients completed their treatment successfully, and follow-up ranged from 1 week to 6 months. One patient experienced an infection, which resulted in partial graft loss that required replacement with HADWM and NPWT. No additional complications occurred in the other patients. Conclusions: This patient case series demonstrated successful use of HADWM and NPWT, which further supports published studies documenting HADWM success in chronic wounds.
PMCID: PMC3840787  PMID: 24324850
chronic wound; human acellular dermal matrix; lower extremity; matrix; NPWT
24.  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
25.  Assisted closure of fasciotomy wounds 
Bone & Joint Research  2012;1(3):31-35.
Negative pressure wound therapy (NPWT) and vessel loop assisted closure are two common methods used to assist with the closure of fasciotomy wounds. This retrospective review compares these two methods using a primary outcome measurement of skin graft requirement.
A retrospective search was performed to identify patients who underwent fasciotomy at our institution. Patient demographics, location of the fasciotomy, type of assisted closure, injury characteristics, need for skin graft, length of stay and evidence of infection within 90 days were recorded.
A total of 56 patients met the inclusion criteria. Of these, 49 underwent vessel loop closure and seven underwent NPWT assisted closure. Patients who underwent NPWT assisted closure were at higher risk for requiring skin grafting than patients who underwent vessel loop closure, with an odds ratio of 5.9 (95% confidence interval 1.11 to 31.24). There was no difference in the rate of infection or length of stay between the two groups. Demographic factors such as age, gender, fracture mechanism, location of fasciotomy and presence of open fracture were not predictive of the need for skin grafting.
This retrospective descriptive case series demonstrates an increased risk of skin grafting in patients who underwent fasciotomy and were treated with NPWT assisted wound closure. In our series, vessel loop closure was protective against the need for skin grafting. Due to the small sample size in the NPWT group, caution should be taken when generalising these results. Further research is needed to determine if NPWT assisted closure of fasciotomy wounds truly leads to an increased requirement for skin grafting, or if the vascular injury is the main risk factor.
PMCID: PMC3626192  PMID: 23610668
Fasciotomy; Negative pressure wound therapy; NPWT; Vessel loop closure; Infection; Complications

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