Negative Pressure Wound Therapy

Wound Care and Offloading· Also known as: NPWT, vacuum-assisted closure, VAC therapy, wound vacUpdated Oct 2026

Reviewed by Andrew Schox, BSc(Hons) PGradDipPod MPod, October 2026

At a Glance

Negative pressure wound therapy (NPWT) seals a wound with a foam or gauze dressing and connects it by a thin tube to a small suction pump. The pump gently draws fluid out of the wound. It is used for long-lasting wounds and complex sudden wounds, such as foot ulcers in people with diabetes, wounds that have split open after surgery, and wounds being prepared for a skin graft. The best results are seen in diabetic foot wounds, though how sure we can be is still low. A trained health professional applies it and checks it regularly. It can't be used on every wound.

What is it?

Negative pressure wound therapy (NPWT) is a treatment for wounds that are slow to heal. A foam or gauze dressing is cut to fit your wound and placed on or inside it. It is sealed with a clear, sticky film, and a thin tube joins it to a small suction pump. When the pump is on, it gently pulls fluid out of the wound and into a canister (a small container).

You may hear it called a wound vac or VAC therapy (short for vacuum-assisted closure). Smaller single-use versions, such as PICO dressings, are also made.

NPWT is thought to help in two ways. It may draw the edges of the skin closer together, and it may increase blood flow through the tiny blood vessels around the wound. This is thought to encourage new, healthy tissue to grow. These ideas are still being worked out, so they are not yet proven.

What is it used for?

NPWT is used for long-lasting wounds and for complex wounds that come on suddenly. Examples include:

foot ulcers in people with diabetes
pressure ulcers (sores caused by pressure on the skin)
wounds from injuries
wounds that have split open after surgery
skin grafts and flaps (healthy skin moved to cover a wound)
closed surgical cuts

It is also used to get a wound ready for a skin graft or flap surgery, or to hold a wound closed for a short time before surgery.

The best support for NPWT is in diabetic foot wounds, but even there we can't be very sure of the results. Overall, it remains a debated treatment.

Is it right for me?

NPWT suits long-lasting wounds, wounds from injuries, healing wounds and wounds that have split open. It has been used for foot wounds after part of the foot has been removed in people with diabetes, as long as the blood supply to the foot is good enough. Your team will also check that the dressing can be sealed properly. This can be harder in some areas, such as around the groin or genitals.

For the single-use PICO dressings, one local guide asks whether the wound leaks less than 300 mL of fluid over 7 days, is less than 4.5 cm deep, and fits the dressing sizes available. In children it can be harder to apply, and treatment can take longer.

NPWT should not be used if you have any of these:

a bone infection (osteomyelitis) that hasn't been treated
a cancer (malignancy) in the wound
dead tissue covered by a hard black scab (eschar), or gangrene
a fistula (an abnormal channel) that hasn't been explored, other than one connected to the bowel
blood vessels, organs or nerves exposed in the wound
places where blood vessels or bowel have been joined by surgery
active bleeding
difficulty keeping up with the treatment as instructed

If any of these may apply to you, your health team will assess you before deciding on NPWT.

What happens?

A trained health professional applies NPWT and checks it, following local protocols and the maker's instructions. First, they clean the wound, dry the skin around it very well and put on a protective film. A thin non-stick layer goes under the foam so it doesn't stick to the wound or to any exposed bone. If your wound is deeper than 2 cm, or has tunnels or pockets under the skin, a wound filler is also needed.

The pump pressure is set in mmHg (a unit for measuring pressure). It is most often 125 mmHg, though settings vary depending on the wound, and there is no single standard. Too much pressure can cause pain and damage the tissue, and very low pressure tends not to work. So your clinician sets it to suit you and your wound.

The dressing is normally changed three times a week. The canister is changed weekly, or sooner if it fills. You and your clinician will set a treatment goal at the start and check your progress at each dressing change. How many weeks you will need it isn't clear, and it depends on how your wound responds.

If the pump alarms, its display shows what the problem is. This is usually easy to fix.

How well does it work?

How well NPWT works depends on the type of wound. How sure we can be about the results is also low in most cases.

For foot ulcers in people with diabetes, NPWT may help more wounds heal than ordinary dressings, and may lower the chance of amputation. Healing time was shorter by an average of 16.79 days than with standard care. After part of the foot has been removed, it may also help more wounds heal, and healthy new tissue formed faster. Whether it changes the chance of further amputation in these wounds is unclear. Some guidelines suggest using it for diabetic foot problems only within a clinical trial, or as a last-resort treatment to prevent amputation.

For other wounds the picture is mixed:

Open wounds from injuries, including broken bones that break the skin: it isn't clear whether NPWT changes the chance of infection, healing time or pain compared with usual care.
Wounds near the bottom after bowel cancer surgery: no clear benefit was found, so it isn't recommended for every such wound.
Cuts after breast reconstruction surgery: no clear difference in infection or seroma (a pocket of fluid) compared with ordinary dressings.
Other closed surgical cuts: some health service guidance suggests considering single-use dressings for people at high risk of wound infection after surgery.
Pressure ulcers and skin grafts: it is described as helpful, but how much it helps isn't clear.

Benefits are modest at best, so talk with your podiatrist or doctor about what to expect for your wound.

Risks and side effects

NPWT can cause problems, though how often they happen isn't clear. Reported problems include:

the system failing, through a leaking seal, a power failure or a blocked tube
wound infection
pain
bleeding
an allergy to the sticky film or dressing
sore, rubbed or damaged skin, including skin death
less freedom to move around
tissue sticking to the foam

It isn't clear whether serious side effects happen more often with NPWT than with usual care. The warning signs below tell you when to get help.

Afterwards

Your treatment goal is checked at each dressing change. NPWT is stopped when the goal is reached. It is also stopped if your wound has shrunk by less than 15 per cent over two weeks, because it is then not helping enough.

It is also stopped if you have signs of infection, extreme pain or heavy bleeding. Your treating doctor or wound specialist will then review your wound and plan the next steps.

When to see a podiatrist

Book an appointment if

Book an appointment with your podiatrist, without delay, if you have a foot wound that is getting worse, looks infected or isn't getting better, or if you would like to know whether NPWT might suit you.

Seek prompt assessment if

Call your local emergency number if dark red fluid or blood quickly fills the canister, or you are bleeding heavily. Stop the pump, don't take the dressing off, lie flat and ask someone to press firmly over the area with a folded towel. If you are in hospital, tell the nurse or doctor straight away.

If you have a wound and you also feel very unwell, with confusion or slurred speech, severe shivering or muscle pain, severe breathlessness, mottled or discoloured skin, or little or no urine, this could be sepsis: call your local emergency number.

These signs need urgent medical assessment: tell your treating nurse or doctor straight away, without waiting for your next visit.

bright red fluid in the tube
a big change in the colour or amount of fluid in the canister
a fever, pus, a foul smell, or redness that is spreading

If you can't reach them, see your GP today, or go to an urgent care clinic or the nearest emergency department.

Tell your treating nurse or doctor promptly, and don't wait for your next visit, if you have any of these:

sudden or increasing pain
an allergic reaction to the sticky film or dressing
an alarm that won't turn off
a pump that has been off for more than two hours

Frequently asked questions

Can I have NPWT if I have a pacemaker?

People with a pacemaker are advised to keep the PICO pump at least 10 cm away from it at all times. Tell your health team about your pacemaker before treatment starts, so they can plan how you will carry and use the pump.

Is NPWT the same as a PICO dressing?

Not quite. PICO is a single-use form of NPWT. It is mostly suited to wounds that leak less fluid and aren't very deep. Standard NPWT uses a separate pump and canister. Your health professional will choose the type that fits your wound.

Will I need NPWT if my wound is expected to heal well?

Probably not. For wounds that are expected to heal well, ordinary or moist dressings are usually a sensible first choice. NPWT is mainly kept for long-lasting or complex wounds. Ask your podiatrist or doctor why they are suggesting it for your wound.