ABSTRACT
Alternating pressure devices consist of air cells connected to an electrical air pump which alternates the area of the body under pressure. The alternating pressure mattress is the major example in this group. They can be cycled by either air or water. Their sizes are variable and could be designed either for bed or wheelchair cushions. Some cushioning devices were not thick enough to fully contact and support the user’s body contours without bottoming out. When cushion inflation pressure was increased to prevent bottoming out, the ability of the cushion to conform closely to the user’s skin was reduced. Air fluidization is an easy way to achieve many of desirable requirements of patient support with a mechanically simple system. Air is compressed by a blower and then forced through a diffuser and into a mass of granular material. The water bed is a low-pressure support system which more evenly distributes the weight of a body over the total supporting surface.
