VOL: 96, ISSUE: 36, PAGE NO: 2
Vanessa Jones, MSc, RGN, NDN, RCNT, PGCE(FE), is education director, Wound Healing Research Unit, University of Wales College of Medicine, Cardiff[B2] Tanya Milton, RGN, DipCHS, is research nurse,
Foam dressings were introduced about 25 years ago. They are usually made of polyurethane, although a silicone foam was also developed, and provide a soft, absorbent dressing for granulating wounds of varying aetiologies and sizes.
They are also gas-permeable, provide thermal insulation and help to maintain a moist wound environment (Thomas, 1993).
Unlike gauze, foam dressings do not shed fibres or particles, and depending on their formulation they can be used on lightly, moderately or heavily exudating wounds.
These dressings can be left in place for several days without causing maceration, increasing their cost-effectiveness (Bale et al, 1998; Banks et al, 1997; Bowszyc et al, 1995). Most can also be used as secondary dressings.
Polyurethane foams are available in a number of different forms and a variety of shapes and sizes, with or without adhesive borders (Morgan, 1999).
These are made up of open-cell hydrophilic polyurethane foam sheets. They are permeable to gas and water vapour, while their outer surfaces remain hydrophobic (Dale, 1997). Depending on the nature and condition of the wound and the amount of exudate, they may need to be changed anything from twice a day to once a week.
- Practice point
The way in which foam sheets absorb blood or exudate varies according to their formulation. One particular product draws fluid up into a heat-treated surface and then spreads it laterally across the face of the dressing. This means that, to prevent maceration or leakage, the dressing must overlap the wound bed by at least 2-3cm (Thomas, 1996).
Some foam sheets were originally recommended for the management of light exudate only, but a more absorbent version has since been produced that is suitable for moderately to heavily exudating wounds (Banks et al, 1997).
Film-backed foam dressings
These have three constituents: a low-adherent polyurethane net that comes into contact with the wound and is designed to prevent or reduce adhesion, a central layer of hydrophilic polyurethane foam, and a polyurethane film backing that blocks the passage of exudate (Dale, 1997).
They are highly absorbent, can often be left on the wound for several days and can be used on heavily exuding wounds without fear of maceration (Thomas, 1996).
- Practice point
Nurses must be able to identify which surface should come into contact with the wound.
This dressing is also available as a cavity wound dressing, which is made up of foam chips enclosed in a sealed, perforated cover.
- Practice point
The number of dressings inserted into large cavities should be recorded to prevent any from inadvertently being left in the wound.
These consist of a thin microporous sheet of polyurethane foam that has been coated with a hydrophilic adhesive and bonded to a polyurethane film backing. They are highly permeable to moisture vapour and their permeability adapts according to the amount of exudate produced. However, they have limited absorbency and are therefore suitable only for lightly exuding wounds.
These dressings should be changed when the exudate is visible within 1cm of the edge of the dressing or after five to seven days, depending on the type of wound.
Polyurethane foam gels
These are made up of an exceptionally absorbent polyurethane foamed gel placed in the middle of a polyurethane membrane (Banks et al, 1996; Taylor, 1999). They are highly permeable to moisture vapour and are suitable for moderately exuding wounds.
The central island dressing consists of a synthetic polymer that does not contain additives or particles. It can be left in situ for about five days, is water-resistant and can be applied easily to awkward areas such as the heels (Williams, 1994; Collier, 1992).
The original silicone foam dressing was made of a polymer of silicone elastomer and a catalyst. Mixing the two caused a chemical reaction that formed a soft foam which expanded to fit the shape of the wound (Thomas, 1993). Comfortable and easy to use, it provided an alternative to gauze packing.
Silicone foam was reformulated in 1990. Easier and quicker to prepare, it produces a simple foam dressing that can remain in situ for up to a week and can be removed, if need be, by the patient (Miller et al, 1994).
These dressings are suitable for use on lightly exuding cavity wounds, where the margins of the cavity can be seen. They are not able to absorb large amounts of exudate and should never be used in sinuses or fistulae, where there is a danger of foam breaking off and being left in the wound.
Clinical use of foams
An extensive range of foam dressings, both self-adhesive and non-adhesive, is available and their ability to conform to the size and shape of a wound makes them particularly useful for awkward anatomical areas such as the sacrum and heel.
Depending on their composition, foam dressings are capable of absorbing anything from light to heavy amounts of exudate. And their ability to do so while maintaining a moist environment means that they can be removed with a minimum amount of pain (Bale et al, 1998; Bowszyc et al, 1995).
Foams can also be used safely in conjunction with other dressing materials, for example under compression bandages (Bowszyc et al, 1995), or on wounds that are difficult to treat, such as diabetic foot ulcers (Foster et al, 1994). Because they can be left in place for several days, they are also cost-effective (Banks et al, 1997; Bale et al, 1998).
Moderate or large amounts of exudate are often associated with wound infection. Foam dressings are appropriate in such cases because they can be used safely on infected wounds (Hollinworth, 1997).
- Practice point
As with all infected wounds, dressings should be changed more often than normally indicated (Hollinworth, 1997).
Foam dressings have many different compositions and structures so they can be used on a variety of wounds, including leg ulcers, traumatic wounds, minor burns, donor sites, malignant wounds and cavity wounds. They are not suitable for dry necrotic wounds but can be used in conjunction with a debriding agent. For example, with a hydrogel to promote autolysis (Thomas, 1993).n