Industry News
Cell Structure and Its Effect on Fluid Handling
The internal cell structure of a polyurethane foam layer determines how exudate actually moves through the dressing, and this is often overlooked in favor of simply comparing total absorption capacity. Open-cell foams with interconnected pores allow fluid to travel both vertically and laterally, wicking exudate away from the wound bed and spreading it across a broader area of the foam before it reaches saturation. Closed-cell or partially closed structures absorb less efficiently but retain fluid more firmly once captured, which reduces the risk of fluid being expressed back toward the wound under compression, such as when a patient lies on the dressing. Foam dressings intended for exuding wounds under compression bandaging are generally built with a denser, more closed cell structure specifically to resist this reverse fluid flow.
Layer Configuration in Multi-Layer Foam Dressings
Most silicone foam dressings are not a single material but a stack of layers, each performing a distinct function. Understanding this layering helps explain why dressings with similar foam thickness can perform very differently in practice.
| Layer |
Primary Function |
| Silicone Wound Contact Layer |
Atraumatic adhesion, conformability to wound bed |
| Absorbent Foam Core |
Exudate uptake and vertical wicking |
| Fluid Distribution / Superabsorbent Layer |
Lateral spreading, retention under pressure |
| Outer Film Backing |
Bacterial and liquid barrier, moisture vapor release |
A dressing that omits the fluid distribution layer may absorb an equivalent total volume on paper but will tend to pool exudate directly under the wound rather than spreading it, which reduces effective wear time even when the labeled absorption capacity looks comparable.
Foam Thickness and Cavity Wound Suitability
Standard flat foam dressings are designed for surface wounds and generally are not appropriate for deep cavity wounds, since a flat sheet placed over a cavity leaves dead space where fluid can collect and bacteria can proliferate without direct contact with an absorbent surface. Cavity-specific foam dressings address this with a soft, conformable fill designed to loosely pack the wound space, maintaining contact with the wound bed at the base of the cavity rather than only at the surface. Packing density matters here: overly tight packing can restrict blood flow to the wound bed and impede healing, while underfilled cavities leave the dead space problem largely unresolved, so cavity dressings are generally packed to roughly 80% of the estimated cavity volume to allow for tissue swelling without excessive pressure.
Managing Periwound Skin During Extended Foam Dressing Wear
Moisture-Associated Skin Damage Around the Border
Even with a well-absorbing foam core, the periwound skin at the dressing border is exposed to a different moisture environment than skin further away, since it sits at the boundary between the moist wound environment and normal ambient conditions. Repeated low-level moisture exposure at this margin can lead to maceration that is easy to mistake for wound enlargement if not assessed carefully at each dressing change.
Border Design Adjustments That Help
- A wider absorbent margin that extends past the wound edge before the adhesive border begins
- A thinner, more breathable adhesive zone at the periphery compared to the central absorbent pad
- Scheduled dressing changes based on strike-through observation rather than a fixed interval alone, since exudate volume can fluctuate day to day
Selecting Foam Dressings for Use Under Compression Therapy
Venous leg ulcers are commonly managed with a foam dressing applied underneath a compression bandage system, and this combination places specific mechanical demands on the foam that are not relevant for dressings used without compression. The foam needs enough resilience to resist permanent compression set, meaning it should not flatten irreversibly under sustained bandage pressure over several days, since a compressed foam loses much of its absorptive capacity and cushioning effect. Foams validated for use under compression are typically tested for recovery after sustained loading, with acceptable products regaining at least 80–90% of their original thickness after the compression is released, which is a reasonable practical benchmark when evaluating options for this specific use case.
Trimming Foam Dressings Without Compromising Performance
Clinicians frequently trim foam dressings to fit irregular wound shapes or awkward anatomical locations, but cutting through certain layer configurations can compromise dressing performance in ways that are not immediately obvious. Cutting through a superabsorbent core layer can expose absorbent particles at the cut edge, which may lead to particle migration into the wound bed in highly exuding wounds. Dressings with the wound contact layer and absorbent core fully encapsulated within the outer film backing are generally safer to trim, since the film seals the cut edge and prevents direct exposure of internal absorbent material to the wound surface, making this a useful distinction to check before trimming any given product for an irregular wound shape.
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