Vacuum-Assisted Closure (VAC) is a form of Negative Pressure Wound Therapy (NPWT). This technique utilizes a mechanical system to apply continuous or intermittent suction, or subatmospheric pressure, directly to the wound bed. VAC therapy creates a controlled environment that encourages faster and more effective healing for complex or difficult-to-treat wounds. By using a sealed system to manipulate the pressure surrounding the tissue, VAC offers a significant alternative to traditional dressing methods for managing challenging injuries and chronic sores.
How Negative Pressure Promotes Healing
The application of controlled negative pressure initiates both mechanical and biological effects that drive the healing process. This subatmospheric pressure works through two distinct types of strain: macrostrain and microstrain. The visible effect, macrostrain, is the physical contraction of the foam dressing and the wound edges being gently pulled inward toward the center. This action helps to reduce the overall size of the wound and facilitates the even distribution of the vacuum pressure across the entire injury site.
The vacuum creates microstrain, which is a microscopic stretching and deformation of the cells within the wound bed. This cellular stretching is a form of mechanotransduction, triggering a cascade of biological signals that stimulate cell proliferation and migration. The mechanical force also helps to significantly increase blood flow, or perfusion, to the area surrounding and within the wound. Increased perfusion delivers more oxygen and nutrients necessary for tissue repair.
Negative pressure also efficiently removes excess fluid, known as exudate, and other infectious or inflammatory materials from the wound bed. This reduction in fluid volume helps to decrease localized tissue swelling, or edema. Removing this fluid and stabilizing the wound environment reduces the overall bacterial load, minimizing the risk of infection. Together, these mechanisms accelerate the formation of healthy granulation tissue, which is foundational for wound closure.
Key Components of the Therapy System
The VAC therapy system is composed of several integrated parts that work together to deliver and maintain a sealed, controlled environment over the wound. The first component is the specialized dressing material, which is typically a porous, open-celled foam or gauze that is cut to fit the exact contours of the wound. This material is placed directly into the wound cavity and serves as the medium through which the negative pressure is evenly distributed.
The entire dressing and surrounding skin are then covered with a transparent, adhesive film to create a completely airtight, or occlusive, seal. This airtight seal is necessary for the vacuum pump to successfully generate and maintain the prescribed subatmospheric pressure. A non-collapsible tube is inserted through a small opening in the film, connecting the dressing to the rest of the system.
This tubing leads to a collection canister, which safely and hygienically collects the fluid and exudate continuously drawn away from the wound. A portable electronic pump generates and regulates the negative pressure, which is usually set within a range of 50 to 125 mmHg. This pump monitors the system pressure and can be programmed for continuous or intermittent suction, depending on the wound type and the physician’s treatment goals.
Specific Conditions Treated by VAC
VAC therapy is indicated for a wide array of wounds, particularly those that have failed to heal with conventional dressings or are considered complex. A primary application is the treatment of chronic wounds, such as diabetic foot ulcers and pressure injuries. These wounds frequently have poor circulation and are slow to heal, making them excellent candidates for the perfusion-enhancing effects of negative pressure.
The therapy is also used for large, acute injuries resulting from trauma or complex surgical procedures, including open abdominal wounds and sternal incisions. In these cases, the vacuum helps to stabilize the wound and manage the large volumes of fluid produced. VAC is frequently employed to prepare a wound bed for reconstructive procedures, such as skin grafts or flaps.
The negative pressure optimizes the wound surface, making it more receptive to a skin graft. It is also used to secure and stabilize skin grafts immediately after placement. This helps prevent fluid accumulation beneath the graft that could lead to graft failure.
Clinical Management and Safety Considerations
The clinical management of VAC therapy involves careful monitoring and adherence to specific safety protocols. The duration of treatment varies significantly based on the wound’s complexity and its response to the therapy. Dressing changes are typically performed by a healthcare professional every 48 to 72 hours, although highly contaminated or infected wounds may require a change every 24 hours.
Pain management is a consideration, as some patients may experience discomfort, particularly during the initial application of the vacuum or during dressing changes. Medications can be prescribed to manage this pain. The system’s airtight seal must be regularly checked, as a leak will cause the pump to lose suction and render the therapy ineffective.
There are certain contraindications where VAC therapy must not be used. These include the presence of untreated osteomyelitis (a bone infection) and wounds that contain exposed blood vessels, organs, or nerves. The negative pressure should also not be applied over malignant wounds or wounds with large amounts of un-debrided necrotic tissue or eschar. Potential adverse events include bleeding, signs of infection, or localized skin irritation around the adhesive seal.