Although it is well documented that pressure sores are caused by prolonged, high pressure applied to the skin, usually over bony areas, it is only comparatively recently that the importance of skin distortion caused by shear forces, is being understood an accepted. The Charnwood LDC cushion has been designed to specifically remove shear stresses from the skin tissue throughout the buttocks area as well as lowering interface pressures caused by the more readily understood compression forces.
The cushion is available for adults, small emaciated adults and children. We will be pleased to consider making special cushions for extra heavyweight patients or patients needing wedge sectioned cushions or any other special adaptations. Please ask for further details.
We have been asked if the cushions could also be made thinner in section and a 5cm (2") thick cushion is now available. This cushion consists of two Liquid Displacement Cells placed one above the other so that any pressure left after the top cell has conformed to the patient's shape is absorbed by the second cell underneath. This cushion does not have the profiled foam top.
Cushions during use are subjected to unequal loading and most people have a definite preference on which side to sit. Weight is transferred onto the other side to provide pressure relief but cushions are always unequally loaded. The act of loading one side of the cushion automatically alters its characteristics, and the varying degrees of compression within the cushion set up pressure gradients and shear forces. These forces can adversely affect the way in which the cushion cares for the users' often delicate skin tissue.
As weight is transferred from one side to the other, the cushion, if not carefully engineered, can cause the user to wobble and this insecurity discourages them from tilting regularly from one side to the other. Thus, the most essential element of pressure sore prevention, movement, is compromised. The Duplex action design of the Liquid Displacement Cell cushion overcomes these potential problems by providing two entirely separate dynamic supports within one cushion.
"H" = height of cushion which may increase under user as height "h" decreases.
"F" = Area of cushion subject to shear forces due to pressure gradient across width of cushion.
"P" = Compression forces which may cause filling to "bottom" through.
"H" = Height of cushion maintained as height "h" decreases less.
"F" = Area of cushion subject to shear forces much reduced.
"P" = Very even distribution of pressure. Little risk of "bottoming" through.
Constructed from a special laminated polymer sheet, each cell is tested to carry 200 kilograms (420 pounds) before assembly into the cushion. It is estimated that the LDC should carry weights of at least 300 kilograms (630 pounds) before reaching bursting point. The specially formulated gel is treated with biocide to ensure that no bacterial growth occurs in the gel for the entire life of the cushion. The cell is designed to allow gel to flow slowly without causing instability. Full use of patient tilt can still be encouraged with advantage, while pockets in the cell provide extra pressure relief beneath the ischial tuberosities.
The Gel is non-flammable, non-toxic and treated with a biocide which prevents any risk of cross infection - even after long-term usage. The Gel will not develop lumps and if subjected to freezing temperatures can be thawed and use continued without detriment.
The foams used in the cushion are high density and, therefore, high quality. This foam is such high quality that its resilience would normally be too high to provide pressure-relieving characteristics. To overcome this potential problem, the foam has been profiled to lower the resilience without sacrificing the integral quality. As the same foam is used on both sides of the cushion it may be used either way up. This considerably extents the life of the product.
This is a unique polyurethane laminated, multi-stretch, knitted fabric. The multi-stretch characteristics of this fabric further enhance the capabilities of the cushion for relieving the shear stresses that are highly damaging to skin tissue. The polyurethane layer is waterproof yet vapour permeable. The cover is also fire resistant and most are fitted with zip closures. However, where special cushions are made, with cut-outs for example, covers might be permanently stitched or welded in place.
A zip fastener is fitted to enable the interior of the cushion to be regularly examined. The cushion should be positioned in the chair with the zipper on the user's left or right side. This avoids the risk of the user sitting on the zipper and as the highest points on the cushion are the sides, there is far less likelihood of the foam becoming soiled in the event of an accident.
Cleaning is easily achieved by washing over with detergent solution. Where cross infection is a concern, bleach solution may be used but wash again in detergent to prevent damage to the unique "Permalon" cover. This fabric is waterproof, fire resistant, breathable two-way stretch and is protected by "Actifresh". All seams are welded to avoid liquid penetration.
The Liquid Displacement Cell cushion has been assessed by the Department of Orthopaedic Mechanics, University of Salford, England. The Clinical Trial has shown that the LDC cushion reduces peak interface pressure by approximately 400%. When compared to the other products in the trial, the LDC cushion also provided the biggest reduction in shear forces by establishing a better distribution of pressure. A copy of this trial paper, published by the Tissue Viability Society, is available from us.
