Negative Pressure Wound Therapy – A Detailed Guide
- Melissa Bray, Wound Physician
- Dr. Janet Mackenzie, C.M.O.
- June 27, 2023
What is Negative Pressure Wound Therapy?
Negative pressure wound therapy is part of a wide range of options for wound care in a multitude of settings ranging from acute care to home health to long-term nursing care. With the natural phases of wound healing regarded as preeminently intricate systems in the human body, treatments are meant to optimize these cellular processes, prevent infections or delays, and resume the healing of stalled wounds (Source 12). Dozens of dressing and treatment options are available to this end, including the dynamic method of negative pressure wound therapy (NPWT).
The use of negative pressure (reduction of barometric pressure) to remove fluid and debris from the wound while stimulating growth has been around for a surprisingly long time. (Source 8 Shah). In ancient times, healthcare professionals used their mouths to suction the wound for this purpose. Fortunately, since the 20th century, technological advancements have brought a mechanized vacuum that attaches to the wound bed with a sealed sponge and tubing, drawing extracellular fluid into a disposable container. (Source 3 Miller).
Types of NPWT
Conventional NPWT
Ultraportable NPWT
Instillation NPWT (NPWTi)
In conventional NPWT, a foam dressing is placed over the wound, sealed with adhesive and an impervious film and connected to a vacuum pump that creates negative pressure as it removes air from the dressing. (Source 1, 3, 6), This type of device is ideal for heavily exudating wounds or large, deep wounds, as it can manage large amounts of fluid. The limiting factor of these devices is the size of the device and the need to plug it in, which limits the patient’s ambulation and freedom of movement.
It uses a battery-operated system to create suction using a disposable pump and dressing without the need for a canister. (Source 1, 3, 6). These devices are intended to facilitate patient movement and ambulation, eliminating the need for a large bulky device and the need for an outlet connection. These devices are limited to wounds with low to moderate drainage, however, due to the smaller canister capacity.
It is an enhancement to Conventional NPWT that provides irrigation of the wound bed with solutions that can cleanse the wound and/or antibiotic solutions (Source 1, 3, 6). The most common use of these NPWTi devices is in the postsurgical setting, often with open or infected wounds. These devices are typically not used in a home or long-term care setting.
NPWT devices are not changed daily. Conventional NPWT devices are typically changed three times per week. Ultraportable NPWT devices are usually changed once per week, although wound bed dressing material (if used) may be changed once between device changes.
It is important that device alarms are not ignored. If the suction is interrupted – typically by loss of the seal around the sponge – exudate builds up in the wound, and bacteria multiply. The risk of infection mandates that a device should not go without suction for more than a few hours. Patients with NPWT devices should always have a “rescue dressing” or backup dressing order if the device fails to maintain suction.
How Does Negative Pressure Wound Therapy (NPWT) Work
NPWT primarily affects the Proliferative phase of wound healing. The Proliferative phase is a continuous process occurring as an interactive backdrop, unlike the other phases (Hemostasis, Inflammation, Remodeling) that are overlapping yet distinct. (Source 11). During the Proliferative phase, granulation tissue and connective tissue are formed while the processes of immunomodulation, neovascularization, and re-epithelialization take place (Source 10,11,12, 7, 3).
How exactly does NPWT help wound healing? One way is the contraction or “macro-deformation” that occurs with NPWT at -125mmHg, causing a reduction in surface area, thereby reducing the amount of re-epithelialization needed. (Source 12, 10, 2). NPWT also promotes “micro deformation” that occurs when suction through the pores of the sponge at the edge of the wound brings about angiogenesis and other cellular activities such as differentiation, migration, and proliferation (Source 10). Even more, the extraction of inflammatory exudate away from the wound bed offloads tissue compression, thereby allowing for the rejuvenation of microvascular circulation (Source 10). Finally, NPWT also improves the overall wound-healing environment by creating an oncotic and osmotic pressure gradient with the removal of unneeded proteins and electrolytes (Source 10). By assisting the proliferative phase, NPWT plays an important role in wound healing.
Patients typically tolerate NPWT very well. The less frequent dressing changes allow for treatment in outpatient or home settings with ease.
Also, please read our Negative Pressure Therapy Demonstration article containing helpful videos.
Benefits/Evidence-based Outcomes of Using NPWT Over Conventional
In the United States alone, there are 6.5 million people who have chronic wounds (Source 12). What are the multiple benefits that NPWT can provide? Not only does NPWT allow for a non-invasive treatment that improves the quality of life for patients with shorter hospital stays, less need for surgery, reduced dressing changes, and accelerated wound healing, but the use of NPWT leads to a reduction in costs in the areas of staffing and supplies. (Source 1 7, 9). In a Cochrane review of 44 studies (11,403 participants total) comparing the outcomes of NPWT vs. standard dressings on surgical site infections (SSI), there was moderate-certainty evidence showing fewer SSIs (8.7% of participants) than treatment with standard dressings (11.75%) after surgery; RR 0.73 (95% CI 0.63 to 0.85; I2 = 29%). (Source 4 Cochrane).
Research has also supported the use of NPWT prophylactically after total hip and knee arthroplasty. The decrease in post-op complications is thought to be due to the positive effects of micro- and macro-deformation on the tissue edges.
Is NPWT expensive?
What Types of Wounds Can This Therapy Treat?
Pressure Ulcers
Once effectively offloaded, NPWT can be extremely helpful in decreasing the size of the wound as well as managing the significant exudate commonly seen in these sites.
Generally, a continuous pressure of -125mmHg is standard for pressure ulcers located at the hips/sacrum/buttocks.
Diabetic Foot Ulcers
Diabetic Foot Ulcers generally treated with a continuous pressure range from -80mmHg
NPWT cannot be used in patients who ambulate on the wound or patients with acute infection. Compliance with offloading is essential in these patients. If in doubt, it is best to use an alternate dressing material
Postsurgical (trauma, skin grafts, flaps, dehisced wounds, other)
Treatment pressure ranges from -50mmHg to -100mmHg is recommended for skin grafts and other surgical sites (Source 7, 9, 10). Vacuum pressure is typically determined by the amount of exudate and contour of the wound bed.
NPWT is often used as an adjunct in clinic or office applications of allografts, xenografts, and synthetic materials. Outpatient application of these products can be significantly facilitated by NPWT in terms of stimulating tissue ingrowth, managing exudate, and keeping the graft in place.
Burns
Localized full-thickness burn wounds may be treated with a combination of negative pressure in conjunction with a graft. There must be uninjured skin all around the wound to allow for the application of the device’s adhesive film, making it unsuitable for extensive burn injuries.
Partial thickness burns do not typically benefit from NPWT.
Venous leg ulcers
One must be mindful of wound exudate and peri-wound skin when considering NPWT for venous wounds. Many patients with venous disease have severe lichenification and/or maceration, which prevents the effective placement of the adhesive film required for the device. On carefully selected patients, however, an ultraportable device can be useful and allow the patient continued ambulation. The patient still requires standard management of venous insufficiency, including leg elevation and compression.
When should NPWT NOT be used?
There are several contraindications for NPWT. These include:
Presence of remaining necrotic tissue or eschar
Untreated osteomyelitis or other infection
Presence of a fistula
Malignancy in the wound
Exposed major vessels and nerves
High risk of bleeding
Non-viable tissue contains a high bacterial load; leaving this tissue covered in a warm moist environment significantly increases the risk of infection. Most clinicians consider 15% necrosis in a wound bed to have minimal risk; larger amounts of necrotic tissue should be removed before placing a suction device
Much like necrotic tissue, there is a significant risk of exacerbating bacterial growth and increasing infection severity if the wound is covered with an impervious device. NPWT devices can be used once the treatment is completed, however. Use in chronic indolent osteomyelitis is unclear. Many clinicians use NPWT in these patients with success, although close monitoring is paramount.
It connects to a body cavity or organ, such as a chronically draining gastric tube site. Active suction of fluid from these spaces may result in electrolyte abnormalities or problems with systemic fluid shifts.
Given the cellular proliferative effect of NPWT on open wounds, these devices should not be used in malignant wounds. (Source 10).
The sponge of the NPWT device can damage exposed structures in the wound bed when removed. While materials such as microperforated petrolatum gauze can be used between the wound bed and NPWT sponge to prevent sticking, great care is indicated when essential structures are exposed.
Patients at high risk of bleeding due to blood dyscrasias or anticoagulation may not be good candidates for NPWT. If the exudate aspirated into the canister is very bloody, one should consider stopping the device and using conventional dressing materials.
Complications/Pitfalls to Avoid NPWT
Pain
Bleeding
Dehydration
Infection
Foam retention
Improper foam selection
Loss of suction
Skin sensitivity to dressing materials
Watch closely for pain once the NPWT device is placed. Ask patients if they have any pain and observe for signs of pain, such as grimacing or agitation, in patients who are unable to speak. Make adjustments in the application of the device as needed until the patient is comfortable.
If the patient is unable to tolerate NPWT, discontinue and revisit in the future as needed.
Bleeding, though rare, is a serious life-threatening complication of NPWT. When it occurs, it is usually associated with certain types of wounds (vascular grafts) or locations (sternum, groin). It can also be associated with medications (anti-coagulants), hematologic disorders, and the removal of adherent or embedded foam.
It is hypothetically possible for patients to develop dehydration or fluid shifts due to the loss of extracellular fluid in high-output wounds. If patients show signs of fluid imbalance, all possible causes should be investigated and corrected.
Follow infection control and antibiotic stewardship principles when using NPWT as you would with any other dressing. If signs and symptoms of infection are observed, consider using instillation NPWT or discontinuing the device until the infection is treated.
Foam can become adherent to the wound bed. If the foam is forcefully removed, small pieces may break off and remain attached to the wound bed. Removal of embedded foam can cause bleeding; one must be prepared to manage any potential issues that arise.
a. It is helpful to soak foam with saline for at least 15 minutes before attempting its removal.
b. Gentle sharp technique should be used to avoid force that could damage tissue.
c. Once all of the foam has been removed, monitor the wound bed for signs of trauma or bleeding.
Another situation in which foam retention may arise is in wound tunnels or undermined areas. White foam, rather than the typical black, should be used in any tunneled areas. If black foam is placed in a tunnel, it often tears and leaves pieces of foam in an area that cannot be easily visualized.
This is the most common problem seen with NPWT. Given the patient’s risk of having a device in place without suction, it is imperative that suction be re-established promptly.
There are multiple potential causes, including loss of the dressing seal, incorrect placement of the suction drain tube, power source disconnection, nonfunctional batteries, suction tube blockage, and a full canister.
Patients may also turn off the device themselves; patient education is important to prevent this.
The adhesive film used to attach the device can be irritating to the skin. Discontinue if you observe peri-wound sensitivity or inflammation. It is often possible to resume the use of the device after allowing the skin to recover for a week or two.
Damage to the surrounding skin leads to erosion or necrosis. Assure that foam does not extend beyond the wound bed in order to avoid maceration and damage to surrounding skin.
Watch for duskiness or discoloration of the wound bed and edges. If this is observed, consider reducing the device pressure or discontinuing the treatment.
Conclusion
FAQs
Is negative pressure wound therapy effective?
What type of wound is not suitable for NPWT?
How do I know my NPWT device is working?
How do I know if my NPWT device is NOT working?
When do you use NPWT?
Is NPWT prophylaxis for surgical site infection?
What are the disadvantages of NPWT?
Who can use NPWT?
Yes. Everyday experience in wound care tells us that NPWT is useful as wounds improve and heal using this treatment. Studies in this area are difficult to carry out; however, a Cochrane review did show that NPWT decreases the risk of infection in postsurgical wounds. (Source 4).
Wounds with remaining necrotic tissue or eschar, untreated osteomyelitis, the Presence of a fistula that connects to a body cavity or organ, and with Malignancy in the wound (Source 10).
Monitor the device for loss of suction. If the unit power light is on and the sponge is compressed (often described as looking like a raisin), the unit is functioning. Your physician will be following your healing progress.
Check for loss of suction once the wound vac is applied. If the transparent adhesive tape is not lying flat and the machine starts to beep when it is turned on, there is likely a loss of suction. When properly functioning, the sponge should be flat and crinkled, looking somewhat like a raisin.
NPWT can be used for pressure ulcers, diabetic ulcers, postsurgical wounds, vascular ulcers, burns, traumatic wounds, and others. (Source 1, 5, 7, 9).
(Source 4) It decreases the risk. A large review of 44 studies found that NPWT decreases the risk of infection in postsurgical wounds.
It is important to watch for pain, bleeding, dehydration, infection, foam retention, loss of suction, skin sensitivity, skin damage, and damage to blood vessels, soft tissue, or nerves (Source 10, 13, 14).
NPWT is used by many healthcare providers to treat wounds within various specialties. Nurses, PTs, NPs, PAs, and physicians apply these devices in the fields of wound care, surgery, dermatology, emergency medicine, podiatry, vascular, family practice, and many others. (Source 10).
References and Resources
Lincare
Wound evolution
Miller C. The History of Negative Pressure Wound Therapy (NPWT): From “Lip Service” to the Modern Vacuum System. J Am Coll Clin Wound Spec. 2013 Nov 28;4(3):61-2. Doi: 10.1016/j.jccw.2013.11.002. PMID: 26236637; PMCID: PMC4511545.
Norman G, Shi C, Goh EL, Murphy EMA, Reid A, Chiverton L, Stankiewicz M, Dumville JC. Negative pressure wound therapy for surgical wound healing by primary closure. Cochrane Database of Systematic Reviews 2022, Issue 4. Art. No.: CD009261. DOI: 10.1002/14651858.CD009261.pub7. Accessed 25 March 2023.
Liu Z, Dumville JC, Hinchliffe RJ, Cullum N, Game F, Stubbs N, Sweeting M, Peinemann F. Negative pressure wound therapy for treating foot wounds in people with diabetes mellitus. Cochrane Database of Systematic Reviews 2018, Issue 10. Art. No.: CD010318. DOI: 10.1002/14651858.CD010318.pub3. Accessed 25 March 2023.
Dumville JC, Webster J, Evans D, Land L. Negative pressure wound therapy for treating pressure ulcers. Cochrane Database of Systematic Reviews 2015, Issue 5. Art. No.: CD011334. doi: 10.1002/14651858.CD011334.pub2. Accessed 25 March 2023.
Benefits of using NPWT – Blog by Datt Mediproducts
Shah JB. The history of wound care. J Am Col Certif Wound Spec. 2011 Sep;3(3):65-6. doi: 10.1016/j.jcws.2012.04.002. PMID: 24525756; PMCID: PMC3601883.
Ji S, Liu X, Huang J, Bao J, Chen Z, Han C, Hao D, Hong J, Hu D, Jiang Y, Ju S, Li H, Li Z, Liang G, Liu Y, Luo G, Lv G, Ran X, Shi Z, Tang J, Wang A, Wang G, Wang J, Wang X, Wen B, Wu J, Xu H, Xu M, Ye X, Yuan L, Zhang Y, Xiao S, Xia Z. Consensus on the application of negative pressure wound therapy of diabetic foot wounds. Burns Trauma. 2021 Jun 21;9:tkab018. doi: 10.1093/burnst/tkab018. PMID: 34212064; PMCID: PMC8240517.
Zaver V, Kankanalu P. Negative Pressure Wound Therapy. 2022 Sep 9. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. PMID: 35015413.
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Wound Healing: A Cellular PerspectiveMelanie Rodrigues, Nina Kosaric, Clark A. Bonham, and Geoffrey C. Gurtner 26 NOV 2018
https://doi.org/10.1152/physrev.00067.2017
https://journals.physiology.org/doi/full/10.1152/physrev.00067.2017#
Allnurses.com. Specialties, Wound. “wound vac granufoam stuck on wound won’t come off” October 31, 2011.
woundsource.com. ALERT: Serious Complications Associated with NPWT Systems. http://www.soundsource.com. 2008-2022. Kestrel Health Information, Inc.
Zhou M, Yu A, Wu G, Xia C, Hu X, Qi B. Role of different negative pressure values in the process of infected wounds treated by vacuum-assisted closure: an experimental study. Int Wound J. 2013 Oct;10(5):508-15. doi: 10.1111/j.1742-481X.2012.01008.x. Epub 2012 May 29. PMID: 22640026; PMCID: PMC7950603.
ptcws.wordpress.com. Negative Pressure Wound Therapy – The Costs. https://ptcws.wordpress.com/2012/03/04/negative-pressure-wound-therapy-the-costs/#:~:text=Negative%20Pressure%20Wound%20Therapy%20%E2%80%93%20The%20Costs.%20The,NPWT%20group%20and%20%2438%2C806%20in%20the%20MWT%20group.
Role of negative pressure wound therapy in total hip and knee arthroplasty. Marcelo BP Siqueira, Deepak Ramanathan, Alison K Klika, Carlos A Higuera, and Wael K Barsoum
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Published online 2016 Jan 18. doi: 10.5312/wjo.v7.i1.30
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