Clinical Applications of Foam Dressings in Wound Management

Wound healing is a complex process that repairs skin defects through re-epithelialization and scar formation. Wound healing is traditionally divided into three overlapping phases: inflammation, granulation and maturation. Inflammation leads to increased capillary permeability and the accumulation of exudate in the wound bed. In addition to cytokines, exudate contains plasma components, growth factors, proteases and protease inhibitors. During the inflammatory phase, the role of exudate is to promote tissue debridement and clear infection, which in turn prepares the wound bed for re-epithelialization through the formation of a temporary matrix. During the granulation and maturation phases, the degree of inflammation and exudate formation decreases, which allows the healing process to advance.

Over the past 30 years, polyurethane foam has become one of the most commonly used wound dressings for exudate management in moist wound healing. Foam consists of a porous structure capable of absorbing fluid into air-filled spaces through capillary action. The most commonly used foam is polyurethane. Foam dressings vary in thickness and may be adhesive or non-adhesive. Foam is usually supplied with a film backing, the purpose of which is to provide a waterproof and microbial barrier to the environment. Film backings have variable permeability, which affects the ability for moisture evaporation and gas exchange. Other types of wound dressings, such as water-active polymers and colloids, are also commonly used in wound treatment. These non-foam materials absorb fluid by swelling, producing a gel-like substance as the fluid binds with the polymer or colloid.

The wound contact layer of a foam product is particularly important, as it both helps transport exudate into the foam and comes into contact with the skin surrounding the wound. Adhesion to the surrounding skin helps keep the dressing in place and prevents exudate from flowing along the skin, thereby preventing skin irritation and leakage. However, adhesion to the skin may cause irritation, especially when the skin is fragile or the wound dressing needs to be changed frequently.

Generally speaking, foam is a highly desirable wound dressing. Its properties include:
1) the ability to maintain moisture in the wound bed;
2) easy removal while protecting the skin around the wound;
3) protection against bacteria and other infectious agents;
4) maintenance of temperature;
5) mechanical protection, cushioning and conformity to body contours;
6) non-toxic and non-allergenic;
7) ease of use;
8) economical with a long shelf life.

Foam is used to manage partial- and full-thickness acute and chronic wounds, as well as moderate to heavy exudate. Foam can be used as a primary or secondary dressing, combined with an amorphous gel applied to the wound bed to provide moisture. Due to its high viscosity, the hydrogel will not be absorbed into the foam.

Absorbing wound exudate is a key function of foam dressings. Ideally, the absorption rate and capacity of a foam dressing should be balanced with the production of wound exudate. As mentioned above, exudate formation varies with wound type and healing phase. Therefore, the optimal dressing must be selected according to the rate at which exudate forms in an individual wound, so as to avoid the skin around the wound becoming dry or macerated. Product information on the absorption rate, evaporation rate and total capacity of an individual dressing is clinically useful. The variable ratio of foam surface area to wound surface area also affects effective evaporation. Selecting which foam will best match a wound is therefore complex and depends on the underlying characteristics of the patient's wound.

Given that the treatment of chronic wounds involves heavy healthcare costs, there is increasing interest in studying the efficacy of various wound dressings to determine which products most effectively assist wound healing.

The effect of foam dressings compared with other types of wound dressings in patients with chronic venous leg ulcers has recently been studied. In this systematic literature review, the overall conclusion was that polyurethane foam showed no significant difference compared with hydrophilic polyurethane foam in healing time, the proportion of ulcers healed at 12 and 16 weeks, or the healing rate; however, polyurethane foam appeared significantly better than hydrophilic foam at managing exudate, thereby reducing leakage problems, reducing the frequency of wound dressing changes and lowering material costs. A study comparing hydrocolloid with foam also reported similar results and limitations regarding exudate management. In addition, in two studies, hydrocolloid was also assessed as more difficult to remove and therefore more time-consuming than polyurethane foam. Pain and adhesion of the dressing to the wound bed were more common with paraffin gauze than with polyurethane foam.

Diabetic foot ulcers are the result of diabetic neuropathy and may be complicated by peripheral arterial disease. Diabetic foot ulcers affect approximately 15% of people with diabetes at some point during the course of their disease, and affect approximately 1%–4% of people with diabetes at any given time. For diabetic ulcers, the data supporting the selection of the optimal wound dressing are very limited, and there is no evidence that the use of foam products leads to more favorable outcomes compared with gauze dressings and/or hydrocolloid dressings. In a 1993 study, polyurethane foam showed superior results to alginate wound dressings after 12 weeks of follow-up.

Pressure ulcers are ischemic wounds affecting the skin and subcutaneous tissue. Prolonged pressure on the skin from underlying bone or cartilage leads to reduced tissue perfusion, resulting in necrosis and wound formation. The main intervention is prevention by relieving pressure on the threatened tissue area. However, once a wound has formed, basic wound care is needed in addition to relieving pressure on the area and optimizing nutritional status. With regard to pressure ulcers, only limited evidence supports the superiority of foam over other wound dressings. One randomized controlled trial showed that foam improved healing compared with plain gauze in the treatment of superficial pressure ulcers characterized by blisters and abrasions with only partial loss of skin thickness. Similarly, there is evidence that hydrocolloid may be preferable to plain gauze dressings.

Fungal wounds originate from advanced cancer. Such wounds are characterized by heavy exudate, malodor, infection, bleeding and pain. Patients usually have a short life expectancy, and the wounds cause severe psychological distress. To our knowledge, no studies have investigated the effectiveness of foam compared with other wound dressings, specifically for fungal wounds. In clinical "best practice", in the absence of supporting evidence, it is important to choose a wound dressing with sufficient absorbency, namely alginate, to avoid leakage. In addition, the use of silver-containing products may help reduce odor.

Foam dressings are widely used in the daily management of acute and chronic wounds of various etiologies. In general, the evidence supporting the use of foam products over other wound dressings is limited. In clinical practice, foam dressings are easy to use and meet most of the ideal criteria for a dressing used in moist wound healing. Given the general lack of conclusive evidence, wound care professionals should select dressings based on clinical assessment of the wound and the skin surrounding the wound.