Negative Pressure Wound Therapy (VAC)

Negative Pressure Wound Therapy (NPWT), also called VAC (Vacuum-Assisted Closure), is a wound treatment that uses gentle suction to help a wound heal faster and more cleanly. A special sealed dressing is placed over the wound and connected to a small pump, which continuously draws air away from the wound surface.

By creating a low-pressure environment directly at the wound, the therapy does several things at once: it removes excess fluid (called exudate) that would otherwise slow healing, reduces swelling in the surrounding tissue, pulls the edges of the wound gently toward the center, and encourages the growth of new healthy tissue (called granulation tissue). The pump runs continuously or in cycles, and the dressing is usually changed every two to three days by a trained wound-care nurse or doctor.

NPWT is used for wounds that are large, deep, slow to heal, or at high risk of infection. It is suitable for both acute wounds (wounds that appeared suddenly, such as after surgery or injury) and chronic wounds (wounds that have been present for a long time without healing well, such as diabetic foot ulcers).

• Diabetic foot ulcers — open sores on the feet caused by diabetes-related nerve and blood vessel damage
• Pressure injuries (bed sores) — wounds caused by prolonged pressure on the skin, usually in patients who are bedridden
• Venous leg ulcers — sores on the lower leg caused by poor blood return from the leg veins
• Surgical wound dehiscence — when a surgical incision reopens or fails to close properly
• Infected or contaminated wounds that need ongoing drainage and cleaning
• Burns and skin graft sites — to help a transplanted piece of skin attach properly to the underlying tissue
• Traumatic wounds — wounds from accidents or injuries that involve significant tissue loss
• Abdominal wounds left open after surgery (open abdomen management)

NPWT is not suitable for every wound. Doctors will generally not use this therapy in the following situations:

• Wounds with untreated cancer (malignant tissue) in or around them
• Wounds with exposed blood vessels, nerves, or organs that are not adequately protected
• Wounds that still contain dead tissue (called necrotic tissue or eschar) that has not been surgically removed — debridement (cleaning out dead tissue) is usually needed first
• Active, uncontrolled bleeding from the wound
• Patients with certain clotting disorders or who are taking strong blood thinners, unless their doctor has carefully assessed the risk
• Known allergy to any component of the dressing used

NPWT is generally considered safe, but like any wound treatment, it does carry some recognised risks and possible complications.

• Pain or discomfort during dressing changes — this is the most commonly reported issue; pain relief is usually offered beforehand
• Skin irritation or allergic reaction around the edges of the sealed dressing
• Bleeding from the wound, especially if the suction level is too high or the wound is near a blood vessel
• Retained dressing material — small pieces of foam or gauze can occasionally be left behind if dressing changes are not done carefully
• Wound infection — while NPWT helps reduce the risk of infection, bacteria can still develop under the dressing if it is not changed on schedule
• Fistula formation (an abnormal channel) — a rare complication in which the suction creates a connection between the wound and a nearby internal organ or structure
• Device malfunction — the pump may alarm, lose suction, or develop a leak in the tubing, which can interrupt therapy and require prompt attention from nursing staff

Preparation for NPWT depends on whether it is being applied in an outpatient wound clinic or as part of a hospital stay. In either case, the medical team will assess the wound thoroughly before starting. Because NPWT is a local wound treatment rather than a general operation, extensive fasting is not usually required — but your care team will give specific instructions based on your overall condition and any other procedures planned at the same time.

Before the dressing is first applied, the following steps are commonly taken:

• Medication review: The team will check all current medications. Blood thinners may need to be paused or adjusted if there is a bleeding concern. Antibiotics may be prescribed if the wound is infected.
• Smoking and alcohol: Smoking impairs wound healing significantly. Patients are strongly advised by their doctors to stop or reduce smoking before and during NPWT. Alcohol intake should also be limited, as it can affect both healing and medication effectiveness.
• Blood tests: A full blood count (a test that checks red and white blood cells and platelets) and blood sugar levels are usually checked, especially in diabetic patients.
• Wound assessment: The wound is measured, photographed, and assessed for any dead tissue, infection, or exposed structures. A wound swab (a cotton-tip sample taken from the wound) may be sent to the laboratory to identify which bacteria are present.
• Wound debridement (surgical or bedside cleaning of dead tissue): If dead or infected tissue is present, it is usually removed before NPWT is applied, so that the suction can work on clean, viable tissue.
• Allergy check: The team will confirm whether the patient has any known allergies to dressing materials or adhesives.

Once the wound is ready, the NPWT dressing is applied in the following steps:

• 1. The wound and surrounding skin are cleaned and dried.
• 2. A piece of foam or gauze (the type depends on the wound and the product used) is cut to fit the exact shape and depth of the wound and placed inside it.
• 3. A clear, airtight adhesive film is placed over the foam and the surrounding skin, sealing the wound completely.
• 4. A small hole is cut in the film, and a suction pad connected to flexible tubing is attached over the hole.
• 5. The tubing is connected to the portable pump unit.
• 6. The pump is switched on and set to the suction level chosen by the doctor. The dressing will visibly compress (shrink inward) as the suction begins.
• 7. The team checks that the seal is airtight and that the pump is working correctly before leaving the patient.

After NPWT is started, the wound is managed as an ongoing process rather than a single event. Patients may be cared for in a hospital ward, a specialist wound clinic, or at home with a portable pump, depending on the wound's severity, the patient's overall health, and the resources available. The therapy continues until the wound has healed sufficiently — either closing on its own or becoming ready for a surgical procedure such as skin grafting or stitching.

• Dressing changes: The foam or gauze dressing is usually changed every two to three days. Dressing changes may be more frequent if the wound is heavily infected. Pain relief is typically offered before each change.
• Pump monitoring: The pump must remain connected and powered at all times for the therapy to work. Nursing staff or the patient's family (if at home) will be shown how to respond to alarms and how to check for leaks in the seal.
• Mobility: Many patients can move around with a portable pump unit. The care team will advise on how much movement is safe and whether the affected limb or body area needs to be elevated (raised above heart level) to reduce swelling.
• Wound inspection: At each dressing change, the nurse or doctor will measure the wound, check for signs of infection (such as increased redness, warmth, smell, or discharge), and document the progress.
• Nutrition: Good nutrition — especially adequate protein and blood sugar control in diabetic patients — is considered an important part of wound healing. A dietitian referral may be arranged.
• Blood sugar management: For diabetic patients, keeping blood sugar levels within the range recommended by the doctor is essential, as high blood sugar slows healing and increases infection risk.
• Follow-up appointments: The frequency of follow-up visits depends on whether the patient is hospital-based or outpatient. The treating doctor will set a schedule and decide when NPWT can be stopped and what the next step in wound closure will be.
• Signs to report immediately: Sudden increase in pain, heavy bleeding through or around the dressing, fever, or a strong unpleasant smell from the wound should be reported to the care team without delay.