Negative-pressure wound therapy is a medical technology that helps certain wounds heal by applying controlled suction through a sealed dressing. It is often used for surgical wounds, pressure injuries, traumatic wounds, and some ulcers when a clinician decides that extra fluid removal and protection are needed. The goal is to create a clean, moist, protected healing environment while reducing swelling around the wound.
This treatment matters because better fluid control can support tissue repair and may reduce the number of dressing changes needed.
A typical system includes foam or gauze placed in the wound, an adhesive film that seals the area, tubing, a fluid collection canister, and a portable vacuum pump. The pump creates pressure below atmospheric pressure, often around -75 to -125 mmHg, which gently pulls fluid and infectious material away from the wound. The suction can also help draw wound edges together and encourage blood flow and granulation tissue formation.
Safe use requires correct sealing, pressure settings, canister monitoring, and regular assessment by trained healthcare professionals.
Key Facts
- Negative pressure means the pressure at the wound is lower than surrounding air pressure.
- Common therapy settings are about -75 to -125 mmHg, depending on the wound and clinician order.
- Pressure difference can be written as ΔP = Pinside - Patmosphere.
- Fluid removal rate depends on suction pressure, tubing resistance, dressing seal, and wound drainage.
- A sealed dressing is essential because air leaks reduce suction and make the pump less effective.
- The system usually includes wound filler, adhesive film, tubing, a vacuum pump, and a collection canister.
Vocabulary
- Negative pressure
- Negative pressure is a pressure lower than the surrounding atmospheric pressure, creating suction.
- Wound dressing
- A wound dressing is a sterile covering that protects a wound and can help control moisture and infection risk.
- Canister
- A canister is the container that collects fluid removed from the wound by the suction system.
- Granulation tissue
- Granulation tissue is new connective tissue and tiny blood vessels that form during wound healing.
- Seal
- A seal is an airtight barrier that lets the pump maintain the correct suction at the wound.
Common Mistakes to Avoid
- Thinking stronger suction is always better is wrong because too much negative pressure can damage tissue or cause pain.
- Ignoring a small air leak is wrong because even a small leak can prevent the dressing from maintaining therapeutic pressure.
- Letting the canister overfill is wrong because it can block fluid removal and interfere with pump function.
- Using the device without wound assessment is wrong because some wounds or conditions may not be safe for negative-pressure therapy.
Practice Questions
- 1 A wound therapy pump is set to -125 mmHg relative to atmospheric pressure. If atmospheric pressure is 760 mmHg, what is the absolute pressure at the wound in mmHg?
- 2 A canister can safely hold 300 mL of fluid. If a wound drains 25 mL per hour, how many hours will it take to reach the safe limit?
- 3 Explain why an airtight dressing seal is necessary for negative-pressure wound therapy to work effectively.