The invention relates generally to seating cushions for the prevention of pressure sores and, more particularly, to a sensor for connection to an inflated air cell cushion that detects a loss of air pressure in the air cell cushion resulting in a change in immersion depth of the seated patient and possible “bottoming out” on a relatively hard support surface.
Air cell cushions are known to the art. Generally air cell seat cushions are used by individuals who must remain seated for extended periods of time, for example, a disabled individual who uses a wheelchair for locomotion. Larger air cell cushions, generally configured as mattresses, are used by non-ambulatory or bed ridden individuals. In any event, inflatable air cell cushions are employed to prevent pressure sores on the buttocks. These air cell cushions provide support, while distributing weight, generally uniformly through a multiplicity of interconnected air cells.
The typical air cell cushion includes a base, and an array of interconnected, upstanding individual air cells, usually arranged in transverse and longitudinal rows. An air inflation tube is in fluid communication with one of the cells. The inflation tube includes a screw type valve. The air cell cushion generally has a stretchy cover. A representative embodiment of such an air cell is disclosed in U.S. Pat. No. 4,541,136, which is incorporated herein by reference.
For proper seating on the cushion, the cushion is placed on a relatively firm or hard support surface, such as a wheel chair seat or other type of seat or chair. The user or caregiver opens the valve and pumps air into the cushion until it is well inflated. The user then sits on the cushion and air is released through the valve until the user is optimally immersed in the air cell cushion. The valve then is closed. Generally, proper immersion occurs when the buttocks of the user are immersed about a half-inch to at the most an inch above the bottom. Proper immersion optimizes weight distribution.
In rare instances, the air cell cushion loses air pressure. The user sinks into the cushion, changing his or her immersion depth until he or she “bottoms out”. That is, the user's buttocks rest directly on the support surface. Many of the individuals who use these cushions have a loss of feeling in the buttocks. Consequently, the user cannot feel that he or she has bottomed out. If the user remains in a bottomed out position, pressure sores can develop on the buttocks, particularly in the ischial area.
Even absent complete bottoming out, a change in immersion depth can change the optimum force distribution characteristics thereby reducing the effectiveness of the cushion in preventing or treating pressure sores.
It would be advantageous, therefore, to have an apparatus that can detect the loss of air pressure in the cushion, change in immersion depth, and the bottoming out of the user and also emit a warning to alert the user or caregiver.