Negative Pressure Wound Therapy (NPWT), or a wound vacuum, is a medical device used to promote healing in complex wounds. This system applies controlled suction, or sub-atmospheric pressure, to the wound bed. Its primary purpose is to manage wounds that are difficult to heal, such as those that are large, chronic, or heavily draining. The suction helps to create an optimal environment that supports tissue repair. This advanced method of wound management has largely replaced traditional techniques, like wet-to-dry dressings, for severe wounds, offering a more active approach to promoting closure and recovery.
How Negative Pressure Wound Therapy Works
The core of NPWT involves a closed system that delivers a regulated amount of suction to the wound surface. This system is composed of several components: a porous dressing, such as a foam or gauze, that is placed directly into the wound; a transparent adhesive film, or drape, that creates an airtight seal over the entire area; tubing; and a portable vacuum pump connected to a collection canister. The pump generates the negative pressure, typically set around -125 mmHg, which is evenly distributed across the wound bed by the foam dressing.
The application of this controlled vacuum triggers biological and mechanical effects that accelerate healing. Mechanically, the suction draws excess fluid (exudate) and infectious materials away from the wound into the collection canister, which significantly reduces swelling (edema). The removal of this fluid alleviates pressure on surrounding tissues and helps stabilize the wound’s microenvironment.
The physical forces exerted on the tissue are categorized as macrodeformation and microdeformation. Macrodeformation refers to the gentle pulling of the wound edges inward, which physically reduces the overall size of the defect. Microdeformation is the cellular-level strain caused by the foam collapsing under suction. This physical stimulation encourages cell proliferation, increases blood flow (perfusion), and promotes the rapid formation of healthy, pink granulation tissue.
Types of Wounds Treated
NPWT is used for a wide range of wounds that struggle to progress through normal healing stages. It is commonly used for chronic wounds, which have failed to heal, including diabetic foot ulcers and pressure ulcers (bedsores) that often form over bony prominences.
The therapy is also effective for acute wounds resulting from trauma or major surgery. Traumatic wounds, such as open fractures or degloving injuries, benefit from the immediate removal of contamination and the promotion of a clean wound bed. NPWT is used on large surgical incisions, especially those with a high risk of breakdown or infection, or following procedures to remove soft tissue.
NPWT can also prepare a wound bed for subsequent surgical procedures, such as a skin graft or flap, by maximizing the amount of healthy tissue present. It is sometimes used on partial-thickness burns, dehisced wounds (surgical incisions that have reopened), and wounds that are draining excessively. The decision to use NPWT is based on an assessment of the wound’s characteristics.
The Application and Wear Process
A trained healthcare professional performs the application of a wound vacuum system to ensure an airtight seal and proper function. The process begins with meticulous cleaning of the wound bed to remove debris and prepare the surrounding skin. Next, a sterile, open-cell foam or gauze dressing is cut precisely to fit the contours of the wound without overlapping onto healthy skin.
Once the foam is positioned, a transparent adhesive drape is placed over the entire area and surrounding skin to create the necessary seal. A suction port is placed over an opening in the drape and sealed. This tubing connects the wound site to the collection canister and the portable vacuum pump.
When the pump is activated, the pressure level is set, often to a continuous setting, and the pump begins to draw air out of the sealed dressing. A successful seal is visible as the foam dressing compresses and the transparent drape wrinkles slightly. The pump is battery-operated and portable, allowing patients to maintain mobility while wearing the device.
Dressing changes are typically performed every 48 to 72 hours, or more frequently if the wound is infected or heavily draining. Removing the adhesive drape and foam can cause discomfort, and measures are taken to minimize pain during the change. The collection canister must be monitored regularly and emptied or replaced as it fills with the removed exudate.
When Wound Vacuums Are Not Used
There are contraindications where NPWT is not appropriate due to safety concerns. The therapy should not be applied over necrotic tissue and eschar that has not been surgically removed, as the vacuum can hinder healing in the presence of non-viable tissue. Wounds that involve exposed organs, blood vessels, or nerves are contraindications because the suction carries a risk of causing serious bleeding or tissue damage.
NPWT is avoided if the wound contains a known malignancy, as the therapy’s growth-stimulating effect could accelerate the spread of cancer cells. In cases of untreated osteomyelitis, the therapy is not recommended until the infection has been addressed. Caution is used with patients who have active bleeding disorders or are taking blood-thinning medications, as negative pressure could increase the risk of hemorrhage. Unexplored fistulas, which are abnormal connections between an organ or vessel and the wound, also prevent the use of NPWT. A thorough clinical assessment is always required before beginning therapy.
Contraindications for NPWT include:
- Necrotic tissue or eschar that has not been surgically removed
- Exposed organs, blood vessels, or nerves
- Known malignancy in the wound
- Untreated osteomyelitis (bone infection)
- Active bleeding disorders or use of blood-thinning medications
- Unexplored fistulas (abnormal connections between an organ or vessel and the wound)