Negative Pressure Wound Therapy (NPWT), widely recognized by the brand name V.A.C. (Vacuum-Assisted Closure), is a specialized treatment for complex wounds. This advanced modality uses controlled, localized negative pressure, or suction, to create an optimal environment that actively promotes healing. NPWT accelerates the recovery of wounds that are difficult to close or have stalled in the natural healing process. By applying consistent sub-atmospheric pressure, the system encourages the body’s mechanisms to repair damaged tissue more effectively than traditional wound dressings.
Understanding Negative Pressure Wound Therapy
Negative Pressure Wound Therapy (NPWT) operates as a sealed, active system rather than a passive dressing. The physical setup involves placing a specialized porous material, such as a sterile foam or gauze, directly into the wound bed. This material is then covered with a transparent adhesive film, which creates an airtight seal over the entire wound area and the surrounding healthy skin.
A drainage tube is connected to the sealed dressing through a small opening in the film, linking the wound site to an external, portable pump unit. Once activated, the pump generates a controlled vacuum that draws air and fluid away from the tissue. The collected wound fluids, known as exudate, are safely deposited into a disposable collection canister attached to the pump.
The therapy can be delivered continuously, maintaining a steady level of suction, or intermittently, cycling between periods of suction and rest. Continuous pressure, often set around -125 mmHg, is typically used to manage high levels of fluid and prepare the wound bed. Intermittent pressure may be selected to provide a more intense mechanical stimulation to the cells for specific phases of healing.
The Science Behind Accelerated Healing
The controlled suction applied by the NPWT system initiates biological and mechanical effects that accelerate tissue repair. The first is macrostrain, which is the gentle drawing of the wound edges inward toward the center. This physical tension reduces the overall size of the defect, making it smaller and easier for the body to bridge with new tissue.
At a microscopic level, the negative pressure induces microstrain, causing a mechanical stretch and deformation of the cells within the wound bed. This cellular stretching stimulates cell proliferation and migration to fill the open space. This mechanical stimulation is a major driver in the formation of healthy granulation tissue, the pink, granular tissue that signals active healing.
The continuous removal of excess interstitial fluid is another major mechanism, which directly addresses edema, or swelling, in and around the wound. Edema hinders the transport of oxygen and nutrients to the injury site. By removing this fluid, NPWT reduces tissue compression, which subsequently improves local blood flow and perfusion in the smallest blood vessels. This ensures the healing tissue receives the necessary oxygen and building blocks for repair.
The system also creates a stable, closed environment that manages fluid and reduces the risk of bacterial contamination. By stabilizing the wound and improving blood supply, NPWT helps promote angiogenesis, the formation of new blood vessels. This improved vascular network is necessary to sustain the rapidly growing new tissue, solidifying the foundation for eventual wound closure.
Clinical Applications of Negative Pressure Therapy
NPWT is frequently indicated for complex and chronic wounds that resist conventional treatments. A primary application is managing chronic ulcers, including diabetic foot ulcers, venous insufficiency ulcers, and pressure injuries. The therapy helps prepare the wound bed for closure, especially in wounds with poor circulation.
The system is also widely used for acute wounds resulting from trauma or significant surgical procedures, such as dehisced incisions where a surgical wound has split open. Applying NPWT helps manage fluid and infection risk, while actively promoting the granulation tissue growth needed for a successful secondary closure.
In plastic and reconstructive surgery, NPWT prepares wounds for skin grafts, creating a clean, well-vascularized bed to maximize graft survival. The controlled pressure also helps secure the graft onto the recipient site, a process known as graft stabilization. Conversely, the therapy should not be applied to wounds with exposed organs, blood vessels, or nerves, or where there is untreated osteomyelitis (bone infection).
What to Expect While Using a VAC Device
Since the pump unit is portable and battery-operated, patients using a VAC device can maintain mobility and continue many normal daily activities. The devices produce a low whirring or pumping sound, which is generally quiet, though it can be noticeable, particularly at night.
The specialized dressing is typically changed by a healthcare professional two to three times per week, depending on the wound type and fluid drainage. During the application of negative pressure, patients may feel a mild sensation of pulling or tightening in the wound area, but significant pain is uncommon. Persistent or sharply increasing pain should be reported immediately, as it may signal an issue with the dressing seal or the wound itself.
The pump unit monitors pressure and will sound an alarm if it detects a leak in the seal or a blockage in the tubing. Patients and caregivers receive instruction on how to check for air leaks and troubleshoot common issues. The duration of therapy varies, ranging from a few days to several weeks, until the wound is prepared for final closure or has healed completely.