Foam dressings are one of the many absorbent dressings available in the market now days. A normal foam dressing has an absorbent porous hydrocellular polyurethane center. This dressing is then laminated with a semiocclusive outer layer.
Different types of foam dressings have varying Moisture Vapor Transmission Rates (MVTRs) of their outer layers.
Moisture Vapor Transmission Rates basically defines the capacity of the foam to absorb. i.e. a dressings with a higher Moisture Vapor Transmission Rates are said to be semiocclusive and allow evaporation of moisture.
Foam dressings with a higher MVTR have greater absorbent capacity and are sturdier i.e. they have longer wear times as compared to occlusive backings that have a lower MVTR.
Second generation foam dressings could have pores of variable sizes. This allows partial fluid retention in addition to fluid exchange. If a dressing has larger pore sizes this will permit moisture to be exchanged between the base of the ulcer and the dressing on the other hand smaller sized pores get saturated and hold back moisture from the wound.
Moisture is retained below the polyurethane backing in the lacunae of the cells. An area where foam dressings come in handy is when the wound is highly exuding. The dressing helps keep periwound maceration and the tissue damage associated with it to a minimum.
Dressings made of foam are said to be nonocclusive and as a result are permeable to gases and water. This is helpful as it lets the wound bed to breathe and permits quick evaporation of excess moisture.
A foam dressing without an occlusive backing the excess moisture will slowly evaporate from the exposed surface of a highly exuding wound. Also the fluid might transfer to more absorbent secondary dressing.
These dressings are mostly if not always nonbioresorbable and nonadherent. The good thing about these kinds of dressings is that they can be shaped to fit wounds of any size easily. This includes wounds that have deeper cavities.
Some specific foams come with a secondary coating which is at the dressing and wound surface junction. These specific dressing might have an adhesive or soft silicone layer. The purpose of the silicon layer is to reduce trauma that might happen to the wound bed and also pain suffered by the patient during dressing removal.
Foam dressings are indicated for use with highly exudating venous ulcers but are contraindicated in dry wounds as in dry wounds there is no requirement of absorbency of moisture.