Dynamically Adaptive Wheelchair Accessory Device for Prevention of Pressure Sores

There is an invisible problem among people with spinal cord injuries. Paraplegics and quadriplegics are plagued by pressure sores (decubitus ulcers) because of the loss of feeling and mobility in the lower body. These ulcers result from lack of circulation due to pressure on the soft tissues. Ulcers can be large and can extend to the bone. Typically, post surgical confinement to bed degrades the health of the patient, beginning a downward health spiral. Several products exist that delay the formation of sores, but currently there is no clinically tested product on the market that prevents their formation.

Care for pressure sores in general is a major expense, estimated at $3-5 billion a year in the US. People who use a wheelchair for more than eight years have a better than 80% chance of developing at least one pressure sore. Over 60,000 deaths annually in the US are attributed to pressure sore complications. An average hospital stay of 90 days is required for a typical severe sore.

To address the problem of pressure sore formation, Numotech Inc. teamed with Sandia National Laboratories to design and build a seat cushion to prevent pressure sores. This effort improved on the older Numotech, Inc. version and brought all components within the cushion, improving reliability and safety, reducing power requirements, and improving battery performance. The cushion works by alternately inflating and deflating air bladders between a form fitting shell and the user. Thus, the seat itself shifts the weight distribution every few minutes, rather than requiring the user to remember to periodically change position. The prototype cushion was FDA approved after clinical testing at a VA hospital. During clinical testing, patients with active ulcers sat on the prototype cushions for up to eight hours per day and their sores healed.

A substantial amount of work will be done on the industrial engineering of piece parts in quantity and on efficient assembly of the finished product. Optimization of materials, fabrication method, formal part and assembly drawings, molds, jigs, and other production issues will also be part of this project. Design issues such as a removable battery box, base plate design and attachment, battery charger, control circuit redesign, and integrated valving will be resolved.

Future potential applications extend past the prevention of pressure sores to reduction of fatigue in professions that require long periods of sitting, such as truck driving and even office work.