Overview

Foam dressings are made of polyurethane or silicone, enabling them to handle large volumes of wound fluid. They are available in a range of thicknesses, adhesive and non-adhesive formulations. They can be used on top of hydrogels and creams or as primary dressings and are useful in reducing over granulation when applied with slight pressure. Some modern foam dressings have been shown to be as effective as cavity fillers. When applied to such wounds, foam has the ability to absorb exudate, preventing pooling and skin leakage, whilst maintaining low adherence to facilitate easy, painless removal (58). Examples: Allevyn and Biatain. Indications: Wounds with moderate to heavy exudate. Pros: Moist wound environment, highly absorbent and protective Permeable to oxygen and water vapour Cons: Will not debride hard exudate, opaque, costly.  Notes: should be avoided in dry wounds, necrotic wounds and those with hard eschar (58).

 

Description of System

Foams were one of the first 'modern' dressings to be used in wound management and became widely available in the mid-1970s. The first commercial 'foam-like' wound dressing was an artificial medicated sponge manufactured by Burroughs Wellcome & Co in the 1880s. This was made from gauze, cotton and coconut fibre, and had an antiseptic containing centre capsule. Today, foam dressings are available in various forms and come in a range of sizes and as sheets, with or without adhesive borders. Foam dressings are available for cavity wounds and are used as a dressing medium in negative pressure wound therapy (V.A.C. ® Therapy and Renasys Go). Also, foam is used in pressure-reducing devices such as mattresses and heel protectors (58).

 

Foams are recommended for leg ulcers, and may be used under compression and on donor sites, skin tears and minor burns. They can be employed as a secondary dressing – particularly as a covering for primary dressings such as amorphous hydrogels. Due to the structure and the viscosity of the hydrogel they are not absorbed into the foam. Although many dressings are classified as a 'foam' there are differences in chemical makeup (58).

 

True foams are soft, open-cell hydrophobic and hydrophilic, non-adherent dressings with single or multiple layers. The surface of the dressing is hydrophilic and is placed on the wound to allow exudate to pass through. The main structure of the dressing is hydrophobic, allowing fluid to be held within the dressing. True foam dressings are absorbent and permits passage of exudate through the non-adherent surface to be absorbed in the main body of the product. It maintains a moist environment as the contact material is hydrophilic, provides thermal insulation, provides cushioning and comfort in situ, does not release particles into the wound, is non-occlusive and gas-permeable due to their open cell structure. True foams can be composed of polyurethane or silicone (58).

 

Polyurethane foams:  The first foam dressings attempted to mimic the action of the sea sponge with a polyurethane construction that contained many air spaces. Polyurethane foam dressings can be used as topical dressings and cavity wound dressings. Cavity wound dressings are available in pre-formed shapes (circular or sausage-shaped) and contain chips of foam encapsulated within a layer of thin, conformable, perforated polymeric film. Exudate passes through the outer layer and is held within the foam chips (e.g. Allevyn Cavity devices). Some foam dressings have an adhesive frame; providing a waterproof backing (e.g. Allevyn Adhesive and Lyofoam Adhesive). There are also charcoal-impregnated foam dressings (e.g. Lyofoam C).

 

A polyurethane foam dressing is also used as part of the structural components of a negative pressure wound therapy system. These foams are available in two forms, depending on the wound type. Some foam and foam-like dressings incorporate silver into the foam structure and release various levels of silver into the wound and/or hold the silver within the structure of the foam to kill bacteria as they are absorbed (e.g. Acticoat Moisture Control) (58).

 

Silicone foam dressings were first developed in the 1950s and were mostly used in pilonidal sinus cavity wounds. Silastic foam was introduced in the 1970s and comprises of a two-component product presented as two separate liquids, a polymer and a catalyst. Modern products are easier and quicker to prepare and can remain in situ for up to a week. Cavi-Care for example, is a version of the silastic foam used in post-pilonidal sinus excision and in some types of dehisced surgical wounds (58). 

 

 

 

 

 

 

 

 

 

 

 

 

Mechanisms Involved

The mode of action of true foams is to draw fluid into the air spaces by capillary action. The fluid is then held within the structure or dispersed by evaporation (58). Silicone foam dressings: When mixed together and poured into a cavity wound, they react, releasing heat and expanding to form a more solid structure that conforms to the shape of the cavity. Silastic foam is able to expand to about four times its original volume (58).

 

Costs and Evidence

Foam has a significant role in the clinical management of chronic wounds and in moist wound healing. There are only a few randomized controlled trials, which in general, show no significant difference in the healing effect of different dressing types. The choice of wound dressing should therefore be based on clinical evaluation of the wound and the skin around the wound (60). A small evaluation demonstrated that soft foam dressings has both clinical benefits and cost benefits. Clinically, it managed wound exudate well. Cost savings were also realised across all wounds. An average weekly saving per patient of £72.71 was demonstrated in chronic wounds (61).