Topical Negative Pressure (TNP)


This leaflet is intended to provide you with information on the technique and give answers to some of the questions you might have about the therapy. If the treatment was initiated by the Tissue Viability team please contact the service below otherwise speak with the ward manager

What is Topical Negative Pressure therapy?

TNP is short for Topical Negative Pressure Therapy which is a system that uses controlled negative pressure (vacuum) to help promote wound healing. Clinical studies demonstrate that TNP therapy also removes infectious materials and other fluid from the wound.

How does TNP therapy work?

The TNP therapy system consists of a computer controlled therapy unit, canister, sterile plastic tubing, foam dressing and clear drape. The foam dressing will go on or inside your wound. One end of the tube will connect to the foam using a T.R.A.C. pad ® the other end will connect to the canister, placed inside the TNP system. The wound area will be sealed with the clear plastic drape. The TNP system pulls infectious material and other fluids from your wound through the tube and collects inside the canister. Additionally TNP therapy enhances blood flow and can decrease swelling, thereby helping the wound to heal.

How does it feel when first applied?

When the TNP system is first turned on, you will feel a slight pulling sensation, if you have any feeling in the wound area. You must keep the system connected in order for it to work. Leaving the system off for longer than two hours per day may result in delayed healing.

How long will I be receiving TNP therapy?

The amount of time you require TNP therapy depends on the type and severity of the wound, your body’s ability to heal wounds and the type of outcome desired. Your clinician or Specialist Nurse will decide whether your wound will be taken to complete closure or ready for a flap or skin graft. However, studies have shown TNP therapy, in most cases, significantly reduces recovery time for patients, even in wounds previously considered non-responsive. Please note that failure to comply and to follow advice could hinder your wound healing.

How many hours a day does the VAC system need to be on?

It is recommended that you remain on the TNP therapy for 24 hours a day, otherwise your wound is not receiving the full benefit of TNP therapy, and you may be at greater risk of complications. If the system is turned off for longer than two hours the dressing must be removed and a new dressing put in place.

How does it feel during treatment?

Patients placed on TPN therapy describe it as a “mild pulling sensation” that is generally not noticeable after around 10-15 minutes. Certainly the level of comfort will vary from patient to patient. Please contact the nurse if discomfort persists.

How often does the dressing need to be changed?

This will depend on the size and type of wound. Usually most TNP dressings will be applied and stay insitu for three days. However, some wounds may be 5-7 days. Your Nurse Specialist or clinician will prescribe a treatment plan.

How will I know if the TPN dressing is working?

The TPN dressing will “wrinkle” when therapy is working and will shrink and mould to the size of the wound.

Is TPN therapy safe?

Yes. TPN has been providing therapy to thousands of patients with acute and chronic wounds. TPN therapy is an excellent method to help promote wound healing. It allows the caregiver to monitor delivery of the Vacuum Therapy at the wound site to ensure controlled, consistent and safe therapy.

Can you move around while on TNP therapy?

This depends on the location of the wound and the 

treatment plan prescribed. Please ask your Clinician or Specialist Nurse.

What happens if the system alarms?

The system has both audible and visual alarms that describe the nature of the problem. Please consult your nurse if you are an inpatient in hospital. If you are discharged with TNP, a full list of problems will be explained to you upon discharge.

Please consult the nurse immediately if:

  • If you notice a significant change in colour or consistency in the fluid.
  • You see excessive bleeding under the clear drape, tubing or in the canister
  • You observe redness or odour from the wound
  • You experience increased pain
  • The alarm will not shut off
  • If the therapy has been turned off for more than two hours

As a family member, how can you help?

As a family member or friend of someone receiving TNP therapy you can remind the patient of the importance of using TNP. In addition, when asked, and properly trained, you can assist in changing the dressing and canisters, responding to alarms and monitoring the therapy. Remember, your support and encouragement can make a difference in a speedy recovery!

What happens if I change my mind?

You are entitled to change your mind at any time during your treatment. Simply speak to a member of the Nurse specialists. The dressing will be removed and a conventional dressing will be applied. Should you require any further information please discuss with your nurse or doctor. 

Contact information

Tissue Viability Service
Chelsea and Westminster: 020 3315 5235
West Middlesex: 020 8321 5312


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