Negative pressure wound therapy with instillation: effects on healing of category 4 pressure ulcers

Negative-pressure wound therapy (NPWT) is a noninvasive therapy that uses negative pressure to treat acute and chronic wounds. NPWT has become a widely used option for treating all types of wounds. When used safely as a component of a comprehensive wound treatment program, NPWT has been associated with the promotion of wound healing. However, while NPWT may be beneficial to patients, complications have been associated with its use. Seventy-seven patient injuries and six deaths associated with NPWT in two years prompted the U.S. Food and Drug Administration to issue an alert to healthcare providers. In 2008 and 2009, the Pennsylvania Patient Safety Authority received 419 reports related to the application or management of NPWT. Complications related to NPWT were described in 112 (27%) reports and included bleeding, evisceration of bowel, retained sponges, infection, maceration, and compromise of tissue surrounding the wound. Clinicians can endeavor to prevent patient harm associated with the use of NPWT by employing risk reduction strategies such as appropriate patient selection, proper device application, and frequent monitoring. (Pa Patient Saf Advis 2011 Mar;8[1]:18-25.) INTRODUCTION Acute and chronic wounds affect at least 1% of the population and represent a significant risk factor for hospitalization, amputation, sepsis, and death. The technique of applying negative pressure to a wound to assist in healing has been in use since the 1950s, and the practice has continued to evolve and gain in popularity. The technique is referred to as negative-pressure wound therapy (NPWT), although several other names exist for this technique, such as vacuum-assisted closure, vacuum-sealing techniques, sealed surface wound suction, subatmospheric pressure therapy, and vacuum-pack technique. The technique typically involves inserting foam or gauze dressing into a wound, cavity, or surface; connecting an evacuation tube embedded in the foam or gauze to a vacuum pump; and sealing the area with an adhesive film. The vacuum pump creates an intermittent or continuous subatmospheric pressure in the range of -50 mmHg to -125 mmHg. NPWT acts to reduce edema, promote granulation tissue perfusion and formation, and remove exudate and infectious materials. 2 The popularity of NPWT as an adjunct to wound healing has been attributed to worldwide marketing, assumed safety, and overall cost-effectiveness. NPWT is estimated to cost approximately $100 per day. This includes the cost of dressings ($25 to $60 per change), a canister ($8 to $15 per day), and rental of the vacuum pump ($55 to $58 per day). NPWT has higher material costs than traditional wound treatment therapies (i.e., gauze); however, the cost may be offset by the benefits of reduced healing time, reduced nursing staff time and expense, decreased length of hospital stay, and facilitation of patient transfer to lower-cost care settings. For example, Braakenburg et al. reported that NPWT is associated with significantly lower nursing staff expense due to fewer effort hours than treatment with conventional wound dressings. 3 Similarly, a study of 51 patients in a long-term acute care facility demonstrated that despite a higher product cost, the overall cost of NPWT was lower than topical advanced moist heat strategies. The study calculated that patients treated with NPWT showed a statistically significantly higher average daily rate of volume reduction compared to an advanced moist wound healing group. The cost of wound reduction was $11.90/cm in the NPWT group compared to $30.92/cm in the moist wound-healing group. The authors suggest that when developing a wound-healing strategy, the cost decision should be based on overall expense and not individual product cost. NPWT has been associated with serious complications. In 2009, the U.S. Food and Drug Administration (FDA) issued a warning to healthcare professionals and consumers regarding reports of 6 deaths and 77 injuries over a 2-year period related to NPWT. 5 Bleeding was the most serious injury and occurred in all 6 reported deaths and in 17 of the reported injuries. Twenty-seven of the reports indicated that the patient developed an infection from the original open wound or from retention of dressing pieces in the wound. Foam dressing pieces, either adhering to tissues or embedded in the wound, were observed in 32 of the injury reports; the majority of these patients required surgical procedures to remove the retained pieces, wound debridement, and treatment of wound dehiscence, as well as additional hospitalization and antibiotics. Similarly, healthcare facilities have reported serious complications associated with NPWT to the Pennsylvania Patient Safety Authority, including bleeding, evisceration of bowel, retained sponges, infection, maceration, and compromise of tissue surrounding the wound. Authority reports also describe issues related to application and management of NPWT devices. Improving the Safety of Negative-Pressure Wound Therapy


INTRODUCTION
Acute and chronic wounds affect at least 1% of the population and represent a significant risk factor for hospitalization, amputation, sepsis, and death. 1 The technique of applying negative pressure to a wound to assist in healing has been in use since the 1950s, and the practice has continued to evolve and gain in popularity. The technique is referred to as negative-pressure wound therapy (NPWT), although several other names exist for this technique, such as vacuum-assisted closure, vacuum-sealing techniques, sealed surface wound suction, subatmospheric pressure therapy, and vacuum-pack technique. The technique typically involves inserting foam or gauze dressing into a wound, cavity, or surface; connecting an evacuation tube embedded in the foam or gauze to a vacuum pump; and sealing the area with an adhesive film. The vacuum pump creates an intermittent or continuous subatmospheric pressure in the range of -50 mmHg to -125 mmHg. NPWT acts to reduce edema, promote granulation tissue perfusion and formation, and remove exudate and infectious materials. 2 The popularity of NPWT as an adjunct to wound healing has been attributed to worldwide marketing, assumed safety, and overall cost-effectiveness. 2 NPWT is estimated to cost approximately $100 per day. This includes the cost of dressings ($25 to $60 per change), a canister ($8 to $15 per day), and rental of the vacuum pump ($55 to $58 per day). NPWT has higher material costs than traditional wound treatment therapies (i.e., gauze); however, the cost may be offset by the benefits of reduced healing time, reduced nursing staff time and expense, decreased length of hospital stay, and facilitation of patient transfer to lower-cost care settings. 2 For example, Braakenburg et al. reported that NPWT is associated with significantly lower nursing staff expense due to fewer effort hours than treatment with conventional wound dressings. 3 Similarly, a study of 51 patients in a long-term acute care facility demonstrated that despite a higher product cost, the overall cost of NPWT was lower than topical advanced moist heat strategies. 4 The study calculated that patients treated with NPWT showed a statistically significantly higher average daily rate of volume reduction compared to an advanced moist wound healing group. The cost of wound reduction was $11.90/cm 3 in the NPWT group compared to $30.92/cm 3 in the moist wound-healing group. The authors suggest that when developing a wound-healing strategy, the cost decision should be based on overall expense and not individual product cost.
NPWT has been associated with serious complications. In 2009, the U.S. Food and Drug Administration (FDA) issued a warning to healthcare professionals and consumers regarding reports of 6 deaths and 77 injuries over a 2-year period related to NPWT. 5 Bleeding was the most serious injury and occurred in all 6 reported deaths and in 17 of the reported injuries. Twenty-seven of the reports indicated that the patient developed an infection from the original open wound or from retention of dressing pieces in the wound. Foam dressing pieces, either adhering to tissues or embedded in the wound, were observed in 32 of the injury reports; the majority of these patients required surgical procedures to remove the retained pieces, wound debridement, and treatment of wound dehiscence, as well as additional hospitalization and antibiotics. Similarly, healthcare facilities have reported serious complications associated with NPWT to the Pennsylvania Patient Safety Authority, including bleeding, evisceration of bowel, retained sponges, infection, maceration, and compromise of tissue surrounding the wound. Authority reports also describe issues related to application and management of NPWT devices. The remainder of the reports (20%) involve a combination of some or all of the above categories of events.

How Does It Work?
NPWT is used in the three phases of healing in acute and chronic wounds: the inflammation phase, the proliferative phase, and the maturation phase.

R E V I E W S & A N A L Y S E S
The inflammatory phase is characterized by hemostasis and inflammation and lasts two to five days. 6,7 The proliferative phase is characterized by the formation of granulation tissue and epithelialization. The duration of this phase depends on the size of the wound. The maturation phase is characterized by increased collagen production and breakdown. Tissue contraction occurs during this phase, in which tissue strength reaches 80% of the strength of normal tissue.
NPWT is thought to act by several fluid-based and mechanical processes, including the following: [8][9][10] Stimulation of wound edge retraction.
Negative pressure draws the edges of the wound together.

Stimulation of granulation tissue formation.
Application of mechanical force is thought to slowly deform skin over time because skin and most tissues are viscoelastic. Stretching of the skin stimulates an increased rate of new cell growth and increases the formation of granulation tissue, which is thought to reapproximate wound edges.
Increased local blood flow. Adequate perfusion is essential to proper wound healing in order to provide nutrients and inflammatory mediators and to remove local edema. Increased blood flow also helps to remove bacteria from the wound.

Continuous removal of exudate.
Reduced interstitial edema. Removal of excess interstitial fluid around the wound margins increases capillary blood flow to the wound bed.

Reduced bacterial loads in the wound.
Reduction in the number of dressing changes decreases damage to delicate new tissue and decreases exposure of the wound to nosocomial infection.

Is It Clinically Effective?
Despite widespread use, the evidence is unclear that NPWT provides additional benefit when compared to other conventional wound treatments, such as gel products, bolster dressings, and hydrocolloids. 6 An Agency for Healthcare Research and Quality (AHRQ) evidence report by the ECRI Institute Evidence-Based Practice Center identified 22 systematic reviews published between 2000 and 2008 that covered NPWT. 6 The review included studies reporting data on the use of NPWT on a number of wound types (e.g., diabetic foot ulcers, pressure ulcers, vascular ulcers, burn wounds, surgical wounds, trauma-induced wounds) and studies comparing NPWT to other wound treatments (e.g., gauze, bolster dressings, wound gels, alginates, other topical therapies). AHRQ assessed three systematic reviews as high-quality based on criteria that included duplicate study selection, the likelihood of publication bias, and conflict of interest. None concluded that NPWT provided additional benefit when compared to other conventional wound treatment. However, the systematic reviews all noted the lack of high-quality clinical evidence supporting the advantages of NPWT compared to other wound treatments. Another concern was the large number of prematurely terminated and unpublished trials of NPWT. 11 Nevertheless, AHRQ concluded that NPWT is a safe alternative treatment to other traditional wound treatments. 6 Which Patients Are Candidates?
NPWT is used in healing both chronic and acute wounds. Chronic wounds are wounds that have not completed the process of healing in the expected amount of time, generally 30 days, or have not progressed through the healing process with the expected results. 12 Diabetic foot ulcers, pressure ulcers, venous leg ulcers, and infected sternal wounds are common types of chronic wounds treated with NPWT. Acute wounds are those lasting less than 30 days. Surgical wounds, burn wounds, and trauma wounds are common wounds treated with NPWT. It can also be used as an adjunct to surgery for skin grafts, flap surgery, and wound bed preparation. 12,13 Appropriate patient selection is important to the success of NPWT. As with any wound care regime, optimizing the patient's ability to heal is essential and requires assessment and management of underlying diseases (e.g., diabetes mellitus) and oversight of any anticoagulation and immunosuppressive therapy. 14 Other factors affecting wound healing include hemodynamic stability, nutritional status, blood glucose, fluid balance, and the presence of infection. 15 Bleeding and infection are serious complications associated with the use of NPWT . 16 , 17 Careful consideration must be given to patients receiving anticoagulants and heparin, since these medications may increase the risk of bleeding. Frequent monitoring of activated partial thromboplastin time and/or prothrombin time with international ratio levels is necessary for these patients. Bleeding may occur with the removal of dressing that has adhered to the wound. Bleeding can also occur if the dressing is placed over exposed vessels in or around the wound that have not been covered and protected during the application of NPWT as recommended by the manufacturer. 16

When to Stop NPWT
In the absence of complications, base the duration of NPWT on regular evaluation of wound progress and/or a predetermined treatment goal. Accurate and reproducible measurement of the wound should be recorded weekly. 13 A 50% improvement in wound size over four weeks is a good indication that the wound will heal. In some cases, NPWT can be used until wound closure, although generally it is used until the wound is filled with granulation tissue and ready for skin graft, flap, or standard wound therapy. 19 After initiation of NPWT, evaluate the wound at each dressing change for signs of deterioration, which include erythema, pain, discharge or infection, tissue necrosis, requirement of repeated debridement, surgical interventions, or increased wound size. 16 Stop NPWT if any complication or deterioration of the wound occurs.

PROMOTING THE SAFE USE OF NPWT
Before initiating NPWT, healthcare practitioners should refer to facility policy and be knowledgeable about the manufacturer's instructions for the device. Regular in-servicing and competency updates are essential to ensure safe and successful use of NPWT. Although a number of NPWT devices are available, the basic steps of NPWT are similar: accurate assessment of the patient and wound before initiation of NPWT, appropriate wound-bed preparation, application of the NPWT unit, and monitoring of progress during NPWT, which includes dressing changes and wound reassessment. Education of staff, patients, and caregivers is also essential. The Authority has received reports of events occurring during each step of the process. For each step, risk reduction strategies can promote the safe use of the device and facilitate wound healing.

Assessment
-Review the physician's order. Orders should include the wound cleansing agent, type of vacuum and dressing (i.e., foam or gauze), therapy settings (i.e., intermittent or continuous suction, negative-pressure setting), and frequency of dressing changes. 12, 18, 20 -Obtain a physician's order if an order is not present when the patient is admitted. 12,18,20 -Assess the patient for factors that may place the patient at risk for any complications, such as preexisting bleeding disorders and use of anticoagulants or other medications or herbs that prolong bleeding times (e.g., nonsteroidal anti-inflammatory drugs, aspirin, gingko biloba). 12,18,20 -Assess the wound before initiating NPWT. If the periwound skin shows signs of compromise, such as breakdown or maceration, address these conditions before initiating NPWT. 12,18,20 Wound Preparation Cleanse the wound according to physician order and facility policy before each dressing application. 12,18,20 -Apply minimal mechanical force during each cleaning. 12,18,20 -Consider using 0.9% sodium chloride solution instead of antiseptic or antibacterial preparations. 12,18,20 -Clean the periwound, and protect the intact skin around the wound to prevent breakdown. Skin preparation products provide a protective barrier between the skin and the adhesive dressing, remove skin oils to promote a better seal, and help minimize trauma when the dressing is removed. 12,18,20 Application -In acute or long-term care, a registered nurse who is certified as a wound care specialist may perform the majority of NPWT applications. For all staff, particularly nursing, conduct regular in-servicing and competency updates to troubleshoot alarms, repair leaks, and observe for complications. 12

Patient and Family Caregiver Education
Reports to the Authority indicate that patients have been readmitted because of complications of NPWT. These reports indicate that the education of patients and caregivers regarding NPWT use may have been a factor in the development of complications that resulted in readmission. Ongoing education and discharge instructions for patients and caregivers on NPWT and the use of the device includes the following: 17 -Safe operation of the device (Provide printed patient instructions either from the device manufacturer or specific to the device.) -Troubleshooting audio and visual alarms -Applying or reinforcing dressing application -Recognizing signs and symptoms of complications to report -Contacting appropriate healthcare providers, especially in an emergency situation -Responding to emergency situations, such as the observation of bright red blood in the tubing or collection canister In emergency situations, teach the patient/caregiver to immediately stop NPWT, apply direct manual pressure to the dressing, and activate emergency medical services.
The education of patients who will be discharged with an NPWT device and the patients' caregivers ideally should begin upon initiation of therapy and continue throughout the patients' hospitalization. Return demonstrations are a good way to assess the patient and/or caregiver's understanding and skills.

CONCLUSION
By following the general principles of wound care and implementing best practices related to NPWT, healthcare providers can safely facilitate wound Ensure dressing/drape has not shifted and blocked tubing.
Lower therapy unit and tubing to or below wound level.
Leakage alarm Use leak-detection procedures/tools to help find and repair leak.
Lower therapy unit and tubing to or below wound level.
Blockage alarm Ensure dressing/drape has not shifted and blocked tubing.
Ensure dressing/drape is located on a flat area of the body, avoiding a skin fold.
healing. Widespread use of NPWT suggests that a healthcare provider is very likely to encounter a patient undergoing NPWT. Safe and effective implementation of NPWT requires regular staff in-servicing and competency evaluation.
Clinical staff must be prepared to appropriately apply, monitor, and effectively troubleshoot problems with the device. Staff must also be able to recognize and respond to complications related to NPWT. Patients and family caregivers must also be prepared to apply, monitor, and respond appropriately to issues that may arise if the patient continues NPWT at home.

NOTES LEARNING OBJECTIVES
-Recall the mechanisms of action of negative-pressure wound therapy (NPWT). -Recognize the risk factors for complications associated with NPWT. -Assess potential strategies to manage NPWT using available evidence. -Select appropriate nursing interventions for a patient whose NPWT is interrupted. -Recall components of patient and caregiver education about NPWT.

SELF-ASSESSMENT QUESTIONS
The following questions about this article may be useful for internal education and assessment. You may use the following examples or come up with your own.