Function

One of the most important factors relating to any cushioning product is understanding how it works. What added function does one product have compared to another and how does this relate to the proposed user?

There are a few basic principles that are used during the design of a product and one or more of these principles will be found in every cushion. Sumed provide three cushion types to achieve the same end ie protection for the individual, against unwanted and unnecessary seating problems.

The Principles

• Envelopment
• Added function

Following will be found descriptions relating to the use of different designs to address the same challenges. Choice is an essential part of user satisfaction and it should be remembered that regardless of whether a product works correctly for an individual, if it isn't liked, it isn't working.

The Flowform Range

Envelopment

The heart of a Sumed Flowform product is the module. This is a sealed flexible envelope that contains Flowform liquid. The liquid consists of an inert base liquid to which are added hollow spheroids graded in size, biocides and inhibitors. The liquid lubricates the particles allowing them to move and flow when subjected to external pressure. The construction of the module is critical to the effectiveness of the product. Various ways are used, but each provides peaks of liquid in which the user sits. The peaks are created by the use of weld spots or links to create interruptions in the skin of the module. If these were not there, a hammock effect would be created between the ischial tuberosities and this would cause pressure points and shear forces/gradients.

The different methods of construction of these peaks gives a different level of ability to each cushion in the range.

By using the module the required envelopment is obtained in a stable user friendly product.

Added Function

The added function is given by the fact that the Flowform is "reactive". Any movement of the body or limbs creates a change in the down force. Flowform will move to accommodate a shift in weight; this therefore creates a change in pressure across the seating area. Movement like this stimulates the circulation, helping to prevent occlusion of the microvessels and start of the deterioration of the skin. In those cases where the breakdown of the tissues has already started, the reactive module will help the blood to recirculate and granulate, regenerating tissue in the necrotic area.

It is the ability to efficiently redistribute pressure, either in a static position or as a result of voluntary or involuntary movement, that makes the products so effective.

The Nest Range

Envelopment

The Nest range of cushions approaches the basic principles in a different fashion. Envelopment is catered for by using foam of different thicknesses depending on the user's needs. This function is enhanced by using a contoured ADS base. This helps to redistribute the load over the maximum area possible, which leads to a reduction in tissue stress. An added benefit is that the ABS base helps to eliminate the wheelchair canvas sling effect resulting in a lower transfer height. The anatomical shape of the base with its integral pommel also helps to promote a stable neutral sitting position with natural leg separation. The contoured base also helps to eliminate sacral sitting.

Added Function

The foam pad has on its top surface an Akton^® viscoelastic polymer pad. This provides an important added function to the performance of the product. Akton^® like a fluid, giving uniform support, yet Is actually a soft solid, which will not bottom out. When pressure is applied at an angle to the skin surface, the various layers move over each other causing tissue distortion. This is called shear and different areas of the skin have different tolerances to shear forces. Deformation due to shear occurs where there is friction between the skin and the surface with which it is in contact, eg clothes. The frictional force will hold the upper layers of the skin stationary while the deeper layers move across one another. The Akton^® pad acts like a second skin and provides a reduction in shear across the seating area. Akton^® quickly adjusts to the shape of the body, however it will return to and permanently hold its original shape when not under load.

The Foamax Range

Envelopment

The Foamax cushion also uses an anatomically shaped base to give a better balanced and neutral sitting position. Having a similar shape to that of the Nest range. the overall transfer height is also reduced, by taking up wheelchair canvas slack. Being constructed of a variety of specialist foams, the key to its performance is envelopment. The combination of contoured base, closed cell, moulded, memory and RX foams gives a substantial improvement to the redistribution of pressure and provides a comfortable seating surface for the user.

Added Function

The combination of foams is the secret to the added function of the Foamax range. For a foam cushion to be effective, "spring back", which is normally associated with the use of a single foam, needs to be reduced. By using a contoured centre to which is added a slow recovery memory foam, this "spring back" is substantially reduced. To the bottom of the 4" version we add a closed cell foam to provide additional protection against bottoming out on the base. The thinner version does not have this bottom layer and so care should be taken to ensure the user has sufficient cover over the Ischial area.