Negative pressure wound therapy (NPWT): what it is and what to expect

Negative pressure wound therapy is a dressing system that applies a controlled vacuum to a wound. Kent Community Health NHS Foundation Trust describes it as a medical device system which delivers a negative pressure to the wound, creating an environment that promotes healing. Leeds Teaching Hospitals puts it more simply as gentle suction through a wound dressing connected to a small electrical pump.

It is not a first-line treatment for every wound. Leeds explains that most wounds heal with standard dressings, but sometimes other treatments are needed for more difficult to heal wounds, for example because the wound is large, deep or leaking high levels of wound fluid. Leeds adds that for many patients NPWT is started after surgery.

The treatment is decided and overseen by healthcare professionals. Kent notes that a healthcare professional oversees the use of the system, including its application and regular dressing changes, and that your clinician will seek your informed consent before starting and throughout treatment.

The leaflets list a similar set of intended benefits. They are described as ways the treatment may help rather than as guarantees.

• Removing excess wound fluid, which is drawn away into a canister.

• Increasing the blood supply to the wound.

• Encouraging healthy tissue to form and drawing the wound edges together (the Kent leaflet).

• Protecting the wound from outside contamination or bacteria.

• Reducing healing time.

Leeds explains that a special gauze or foam is cut to the size of the wound. A non-adhesive layer may be used at the base of the wound, with the foam or gauze on top and a sticky film sealing the dressing in place. A tube connects the dressing to the electrical suction pump, which has a collection canister inside it. Once the pump is switched on and the suction begins, it gently draws fluid away from the wound into the canister.

Kent describes the same arrangement and says the canister is changed weekly unless it becomes full, and that the pump should be kept upright so that fluid can drain properly. The pump is portable. Leeds says it usually comes with a bag that you can carry over the shoulder, has an internal battery and can be disconnected from the charger for periods so you can move around, but it is recommended to reconnect it to the power when you are not moving. Kent says the unit needs to be recharged daily, and that each charge should last up to 14 hours.

Leeds says the therapy should not restrict your mobility. If you are unsteady on your feet or concerned about falling, a falls risk assessment can be done by the nursing or physiotherapy team, including before discharge home. Washing needs some thought: the pump must be kept dry. Kent says a brief shower is preferable to a bath, that the nurse will show you how to disconnect the tubing from the pump to avoid getting it wet, and that a bath is only possible if the wound is above the water level because the seal can be affected.

Kent also gives some practical advice for healing: eat a healthy, balanced diet rich in protein, carbohydrates, vitamins and minerals, drink enough fluids, stay active if possible, limit alcohol and stop smoking. It stresses that the therapy should not be left off for longer than two hours as this affects therapy and healing, and that if the pump has not been working for two hours or more you should contact the community nurses, because the dressing will need to be removed and replaced with a conventional dressing while waiting for it to be reapplied.

Wound healing can take time. Kent acknowledges that it is understandable to feel frustrated and anxious, and says that you should feel free to ask the team when and why therapy may begin and end.

Leeds says most people do not have pain with this treatment, although some wounds are painful despite treatment. When the pump is turned on you may feel a pulling sensation, which soon eases. Kent says most patients describe a non-painful, mild pulling sensation, and that the wound may become tender or itch as it heals; if itching or discomfort persists you should speak to your clinician. For dressing changes, Leeds says you can request painkillers before the dressing is taken off, and Kent suggests taking painkillers 30 to 60 minutes beforehand.

Pumps alarm for a range of reasons. Leeds lists a full canister or a blockage in the tubing, low suction (usually because of an air leak in the dressing) and a low battery. In hospital you tell your nurse; at home you contact the equipment helpline, the community nursing team or your GP surgery. Kent advises calling your nursing team if your dressing does not feel right, is leaking, the pump is alarming or you notice fresh blood in the tubing or canister.

Kent explains that NPWT dressings are not placed in contact with exposed blood vessels, over tubular structures such as blood vessels or intestines that are joined surgically, or over organs or nerves. It also lists malignancy in the wound, untreated bone infection (osteomyelitis), unexplored fistulas, and gangrenous or necrotic tissue as situations where NPWT is not suitable. These are decisions for the clinical team, who should discuss the risks and benefits with you.

Leeds adds that NPWT is not suitable for everyone, that it is often a matter of patient preference, comfort and personal choice, and that some patients are not suitable for NPWT at home. If you are unable to move around safely with the pump, you will not be discharged with NPWT and conventional dressings will be used instead.

Who decides: Leeds says the doctors, ward nurse and tissue viability nurses discuss the options with you.

There is no fixed length. Leeds says that it varies for each person and depends on the size and type of wound, and that the doctors and nurses decide how long you need it depending on how your wound is progressing after each dressing change. Kent says that general health conditions, size and location of the wound and nutritional status can affect healing time.

Leeds says that for many patients NPWT is started after surgery, so treatment normally begins in hospital, and that once you are medically fit for discharge but still need NPWT you can be discharged home with it, supported by community nurses or your GP surgery nurses.