Negative Pressure Wound Therapy
Encyclopedia
Negative-pressure wound therapy (NPWT) is a therapeutic technique using a vacuum dressing to promote healing in acute or chronic wounds and enhance healing of first and second degree burns. The therapy involves the controlled application of sub-atmospheric pressure to the local wound environment, using a sealed wound dressing connected to a vacuum pump. The use of this technique in wound management increased dramatically over the 1990s and 2000s and a large number of studies have been published examining NPWT. NPWT appears to be useful for diabetic ulcers but further research is required for other wound types.
from the wound and increases blood flow to the area. The vacuum may be applied continuously or intermittently, depending on the type of wound being treated and the clinical objectives. Typically, the dressing is changed two to three times per week. The dressings used for the technique include open-cell foam dressings and gauze, sealed with an occlusive dressing
intended to contain the vacuum at the wound site. Where NPWT devices allow delivery of fluids, such as saline or antibiotics to irrigate the wound, intermittent removal of used fluid supports the cleaning and drainage of the wound bed.
In 1995, Kinetic Concepts was the first company to have a NPWT product cleared by the US Food and Drug Administration
. Following increased use of the technique by hospitals in the US, the procedure was approved for reimbursement by the Centers for Medicare and Medicaid Services
in 2001.
is fitted to the contours of a wound and sealed with a transparent film. A drainage tube is connected to the dressing through an opening of the transparent film. The drainage tube is also connected to a vacuum
source, turning an open wound into a controlled, closed wound while removing excess fluid from the wound bed to enhance circulation and remove wound fluids. This creates a moist healing environment and reduces edema. The technique is usually used with chronic wound
s or wounds that are expected to present difficulties while healing (such as those associated with diabetes).
Commercial products for the technique are generally divided into three categories based the type of dressing used over the wound surface: open-cell foam
, gauze
or honeycombed textiles with a dimpled wound contact surface. Foam dressings are used to fill open cavity wounds and can be cut to size to fit wounds. The foam dressing is applied, filling the wound and then a film drape is applied over the top to create a seal around the dressing. A vacuum tube is connected through an opening in the film drape to a canister on the side of a vacuum pump. NPWT can be conducted using standard medical supplies such as open weave cotton gauze, transparent film, a flat drain and tubing that connects to a vacuum pump. The flat drain is sandwiched in gauze and this is then placed onto the wound. A film drape is used to cover the wound and create a complete seal, and then the drain is connected to the pump via the tubing. The third type of dressing involves layers of non-woven polyester, joined by a silicone elastomer, and has a non-adherent wound contact surface made up of numerous small semi-rigid dome structures.
With all three techniques, once the dressing is sealed the vacuum pump can be set to deliver continuous or intermittent pressures, with levels of pressure depending on the device used, varying between −125 and −75 mmHg depending on the material used and patient tolerance. Pressure can be applied constantly or intermittently.
The dressing type used depends on the type of wound, clinical objectives and patient. For pain sensitive patients with shallow or irregular wounds, wounds with undermining or explored tracts or tunnels, gauze may be used, while foam may be cut easily to fit a patient’s wound that has a regular contour and perform better when aggressive granulation formation and wound contraction is the desired goal.
stated that the evidence comparing NPWT to alternative care was flawed and required more study, but the evidence did support improved healing and called for more, better quality research to be conducted. A 2010 systematic review
found "consistent evidence of the benefit of NPWT" in the treatment of diabetic ulcers of the feet. Results for bedsore
s was "conflicting" and research on "mixed wounds" was of poor quality, but promising. The review did not find evidence of increased significant complications
. The review concluded "There is now sufficient evidence to show that NPWT is safe, and will accelerate healing, to justify its use in the treatment of diabetes-associated chronic leg wounds. There is also evidence, though of poor quality, to suggest that healing of other wounds may also be accelerated."
Overview
NPWT promotes wound healing by applying a vacuum through a special sealed dressing. The continued vacuum draws out fluidEdema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
from the wound and increases blood flow to the area. The vacuum may be applied continuously or intermittently, depending on the type of wound being treated and the clinical objectives. Typically, the dressing is changed two to three times per week. The dressings used for the technique include open-cell foam dressings and gauze, sealed with an occlusive dressing
Occlusive dressing
An occlusive dressing is an air- and water-tight trauma dressing used in first aid. These dressings are generally made with a waxy coating so as to provide a total seal, and as a result do not have the absorbent properties of gauze pads...
intended to contain the vacuum at the wound site. Where NPWT devices allow delivery of fluids, such as saline or antibiotics to irrigate the wound, intermittent removal of used fluid supports the cleaning and drainage of the wound bed.
In 1995, Kinetic Concepts was the first company to have a NPWT product cleared by the US Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
. Following increased use of the technique by hospitals in the US, the procedure was approved for reimbursement by the Centers for Medicare and Medicaid Services
Centers for Medicare and Medicaid Services
The Centers for Medicare & Medicaid Services , previously known as the Health Care Financing Administration , is a federal agency within the United States Department of Health and Human Services that administers the Medicare program and works in partnership with state governments to administer...
in 2001.
Technique
General technique for NPWT is as follows: a dressingDressing (medical)
A dressing is an adjunct used by a person for application to a wound to promote healing and/or prevent further harm. A dressing is designed to be in direct contact with the wound, which makes it different from a bandage, which is primarily used to hold a dressing in place...
is fitted to the contours of a wound and sealed with a transparent film. A drainage tube is connected to the dressing through an opening of the transparent film. The drainage tube is also connected to a vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
source, turning an open wound into a controlled, closed wound while removing excess fluid from the wound bed to enhance circulation and remove wound fluids. This creates a moist healing environment and reduces edema. The technique is usually used with chronic wound
Chronic wound
A chronic wound is a wound that does not heal in an orderly set of stages and in a predictable amount of time the way most wounds do; wounds that do not heal within three months are often considered chronic....
s or wounds that are expected to present difficulties while healing (such as those associated with diabetes).
Commercial products for the technique are generally divided into three categories based the type of dressing used over the wound surface: open-cell foam
Foam
-Definition:A foam is a substance that is formed by trapping gas in a liquid or solid in a divided form, i.e. by forming gas regions inside liquid regions, leading to different kinds of dispersed media...
, gauze
Gauze
Gauze is a thin, translucent fabric with a loose open weave.-Uses and types:Gauze was originally made of silk and was used for clothing. It is now used for many different things, including gauze sponges for medical purposes. When used as a medical dressing, gauze is generally made of cotton...
or honeycombed textiles with a dimpled wound contact surface. Foam dressings are used to fill open cavity wounds and can be cut to size to fit wounds. The foam dressing is applied, filling the wound and then a film drape is applied over the top to create a seal around the dressing. A vacuum tube is connected through an opening in the film drape to a canister on the side of a vacuum pump. NPWT can be conducted using standard medical supplies such as open weave cotton gauze, transparent film, a flat drain and tubing that connects to a vacuum pump. The flat drain is sandwiched in gauze and this is then placed onto the wound. A film drape is used to cover the wound and create a complete seal, and then the drain is connected to the pump via the tubing. The third type of dressing involves layers of non-woven polyester, joined by a silicone elastomer, and has a non-adherent wound contact surface made up of numerous small semi-rigid dome structures.
With all three techniques, once the dressing is sealed the vacuum pump can be set to deliver continuous or intermittent pressures, with levels of pressure depending on the device used, varying between −125 and −75 mmHg depending on the material used and patient tolerance. Pressure can be applied constantly or intermittently.
The dressing type used depends on the type of wound, clinical objectives and patient. For pain sensitive patients with shallow or irregular wounds, wounds with undermining or explored tracts or tunnels, gauze may be used, while foam may be cut easily to fit a patient’s wound that has a regular contour and perform better when aggressive granulation formation and wound contraction is the desired goal.
Effectiveness
A 2007 Cochrane ReviewCochrane Library
The Cochrane Library is a collection of databases in medicine and other healthcare specialties provided by the Cochrane Collaboration and other organisations. At its core is the collection of Cochrane Reviews, a database of systematic reviews and meta-analyses which summarize and interpret the...
stated that the evidence comparing NPWT to alternative care was flawed and required more study, but the evidence did support improved healing and called for more, better quality research to be conducted. A 2010 systematic review
Systematic review
A systematic review is a literature review focused on a research question that tries to identify, appraise, select and synthesize all high quality research evidence relevant to that question. Systematic reviews of high-quality randomized controlled trials are crucial to evidence-based medicine...
found "consistent evidence of the benefit of NPWT" in the treatment of diabetic ulcers of the feet. Results for bedsore
Bedsore
Bedsores, more properly known as pressure ulcers or decubitus ulcers, are lesions caused by many factors—such as unrelieved pressure, friction, humidity, shearing forces, temperature, age, continence, and medication—to any part of the body, especially portions over bony or cartilaginous areas such...
s was "conflicting" and research on "mixed wounds" was of poor quality, but promising. The review did not find evidence of increased significant complications
Complication (medicine)
Complication, in medicine, is an unfavorable evolution of a disease, a health condition or a medical treatment. The disease can become worse in its severity or show a higher number of signs, symptoms or new pathological changes, become widespread throughout the body or affect other organ systems. A...
. The review concluded "There is now sufficient evidence to show that NPWT is safe, and will accelerate healing, to justify its use in the treatment of diabetes-associated chronic leg wounds. There is also evidence, though of poor quality, to suggest that healing of other wounds may also be accelerated."