There is often a lot of confusion about mattresses, in terms of what is suitable for different patients and what different therapies are offered by different mattress types. Manufacturers will offer some guidance on the suitability of their product, but this can often be ambiguous, with some using terms like “very high risk” to describe foam mattresses, which are generally seen as more suitable for patients at a lower risk of pressure ulcers/bed sores/pressure injuries.
A foam mattress (whether it be high specification foam, or visco-foam/memory foam) uses the therapy of pressure reduction, which spreads the weight of the patient over the largest possible footprint. This is generally suitable for individuals who are at risk of pressure injuries, but where the risk is considered to be low to medium.
An alternating mattress (otherwise known as air wave, air flow, ripple) uses periodic pressure relief. (Again, this is a point of dispute, as it is likely that these system never actually give 100% offloading due to patient movements and “hammocking” of the top cover and bed sheets. It does however give a significant amount of pressure redistribution). This means that cells inflate and deflate allowing areas of the skin to experienced reduced pressure, which allows nutrition and oxygen to reach the skin to prevent breakdown, or to help to heal skin.
There is a broad clinical consensus (EPUAP, NPUAP, PPPIA, NICE Guidelines, RCN etc.) that a deep cell (20cm or 8inch) alternating mattress should be used for individuals at a high risk of developing a pressure ulcer, or with existing skin damage.
The video below shows the principle of how the alternating mattress works. Some systems will alternate with 1 in 3 cells, or even 1 in 4 cells deflated. The most common therapy is 1 in 2 cells deflating, which offers the maximum periods of reduced pressure.