Authors: Christian Kaare Paaskesen Stud. Med, Magnus Balslev Avnstorp, MD, & Hasan Gökcer Tekin MD.

Multiple systems have been developed to preformed NPWT, in this chapter V.A.C and PICO V.A.C will be described.

V.A.C

V.A.C is a negative pressure wound therapy system used in inpatient and outpatient settings (the outpatient setting requires a portable bag). V.A.C can be used multiple times and is commonly used in combination with different types of foams. Black foam has a pore size of 400-600mm, whereas white foam has a pore size of 250mm. White foam has a higher tensile strength and is preferable for undermining wounds compared with black foam, to avoid small pieces of cut foam in the wound. Black foam does not clot as easy as white foam and can transport larger amounts of exudate and generate more granulation tissue. Although, caution is advised in low exuding wounds if the wound dries out and leads to ischemia and necrosis.

The function of foam dressings in NPWT is to distribute an even negative pressure over the whole wound bed. A silver foam is also available for wounds that needs an antibacterial component to ensure healing.

To prevent the foam from sticking to the wound, a silicone dressing (Cuticerin^®) can be used as a primary dressing.

When the foam dressing is applied, a fenestrated evacuation tube is applied, and the site is covered with an adhesive drape. To ensure a water- and airtight site, secure the drape in a 3-5 cm peri wound distance on healthy tissue. The V.A.C. system provides the therapist with a selection of modes to choose from, either a continuous or intermittent (2 – 5 minutes) negative pressure ranging from 50 mmHg to 125 mmHg.  Large and heavily exudating wounds may require a higher pressure(>150mmHg) (1, 2). Intermittent mode is recommended as it generates more blood flow in periods where the vacuum is off. Studies suggest that wound contraction and the formation rate of granulation tissue is improved using intermittent pressure settings on NPWT systems (3).

Moisture assessment

• Low – heavily exuding wounds

Advantages

V.A.C treatment reduces the need of dressing changes and promote patient comfort. It also reduces bacterial load and edema while still maintaining an optimal closed moist environment. Ultimately resulting in faster healing and as a result reduces hospital stay. V.A.C has proven to create granulation tissue, and is widely used to fill out wound cavities. (2)

Some V.A.C. systems also have the ability to perform NPWTi-d and should be used according to manufacture and international guidelines. (4)

Disadvantages

Air leak in the dressing can result in an air flow over the wound, desiccating the wound and forming eschar. Eschar seals the wound with retained exudate and leads to worsening of the wound. Once started, NPWT should not be terminated abruptly after one session, as it may result in what is called “rebound phenomenon” which leads to worsening of the wound. 2-3 sessions should always be planned. V.A.C. requires health-care professionals to ensure right and optimal treatment without technical failures. After 2-3 weeks, the formation of granulation tissue will stop, this is an indication to pause the treatment. 

Available products

• KCI wound VAC system
• Acti V.A.C
• V.A.C. VERAFLO(NPWTi-d)
• Acti V.A.C ulta (NPWTi-d)

Product example:

NWPT.

NPWTi-D

PICO V.A.C

PICO is a onetime use negative pressure wound therapy system. It consists of a pocket-sized pump attached to special developed dressing. PICO is used in an outpatient setting and operates at an 80mmHg negative pressure.

Moisture assessment

• Low – moderate exuding wounds

Advantages

PICO makes it possible to discharge patient earlier while still maintaining active treatment of a wound. This makes it easier for patients to maintain normal day to day activities. Dressing changes are easy and can be performed by patients at home. The PICO is usually to last 14 days before running out of battery, dressing changes are usually indicated after 5-7 days. PICO also removes wound odor through a unique combination of absorption and vaporization.

If necessary, materials like white and black foam can still be used in combination with the PICO. (5)

The PICO device is pocketsize, and easy for patients to carry around.

Disadvantages

Compliance is very important when discharging patients. Information about hygiene and dressing changes must be understood properly, to ensure that the wound bed and peri wound skin do not take damage. The PICO has no cannister for wound exudate, this makes the PICO dependent on the dressing for the maximum exudate absorbance (multiple dressing sizes are available).

Available products

• Smith and Nephew PICO®

Product example: