Vacuum Assisted Closure or VAC therapy is a technique of negative pressure wound therapy which employs vacuum to promote healing of wounds, especially those which are large or chronic. It is an advanced wound healing therapy that came into vogue in 1995 (Thomas, 2001). The procedure was first employed by Fleishmann et al (1993; qtd. in Thomas, 2001). With proper precautions and treatment measures, the therapy can be delivered both in hospital and community settings. This is a technology based treatment involving control by a microprocessor unit and employment of specialized dressings.
VAC therapy helps in wound management by promoting granulation tissue, improving perfusion to the wound, decreasing edema and by removing unwanted exudate and infectious material. The wound healing is enhanced by delayed primary and secondary intentions. Chronic wound fluid which inhibits cell proliferation (Bucalo et al, 1993) is removed by VAC therapy. Perfusion is improved by removing chronic edema. Currently, VAC therapy is used in the management of acute traumatic wounds, partial thickness burns, chronic wounds, dehisced wounds, pressure ulcers, grafts, flaps and diabetic foot ulcers.
Various studies have proved the efficacy of VAC therapy in the treatment of chronic and difficult wounds (Argenta and Morykwas, 2000, Joseph et al, 2000 and Blume et al, 2008). However, the Cochrane review has a different opinion. According to Cochrane review, negative pressure wound therapy is in no way superior to other forms of wound treatment (Ubbink et al, 2008). Components and working of VAC therapy system An open-cell foam dressing is used to cover the wound. There are 2 types of foam dressings; an open pore reticulated polyurethane foam, also known as GranuFoam and a polyvinyl alcohol foam or WhiteFoam.
The foam is covered by a transparent adhesive drape. A tube connects the foam to a canister. Fluids from the wound are drained into the canister by the tube. Negative pressure to the wound bed is applied by a soft-controlled therapy unit. The open cells of the foam allow the negative pressures to be distributed equally across the wound’s surface. The open cells also prevent perforation occlusions of the drain and eliminate localized areas of high pressure. It is important to eliminate localized areas of high pressure to prevent tissue necrosis.
The plastic membrane prevents ingress of air. Negative pressure can be delivered either continuously or intermittently based on the requirements of the therapy. Sensa TRAC is a technology employed in VAC units which relays signals to the therapy unit, and thus helps in delivering, monitoring and maintaining target pressure. The VAC system also consists of alarms which signal tube blockages, full canister, missing collection in canister, inactive treatment, low battery, any leakages in the seal of the dressings and also low pressures delivered than the set limit (KCI, 2007).