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Cushion project aims to fight wheelchair sores

Three MU students built a prototype of a cushion that a user could adjust.
Monday, March 6, 2006 | 12:00 a.m. CST; updated 12:11 a.m. CDT, Thursday, July 10, 2008

When MU student Mike Delger was working on a prototype cushion modification that would help prevent pressure sores for wheelchair users, he ran into problems he didn’t expect.

Delger, along with fellow students Nicole Poythress and Elizabeth Claycamp, worked on the project last semester as part of their senior capstone class in biological engineering. The team tied theory and know-how from throughout the field into a practical device that monitors the air pressure inside a wheelchair cushion and allows the user to easily inflate or deflate it.

When people are sitting or lying down, soft tissue like skin and muscle is sandwiched between bone and the surface on which it’s resting. The resulting pressure causes discomfort, causing people to shift in their seats or roll over for relief. But if a person has limited sensation or is unable to move, these pain cues don’t work. The constant compression of the same areas reduces bloodflow, which then damages tissue and can result in a sore.

Even minor fluctuations in a cushion’s pressure can put a wheelchair user at risk of developing a sore. A very small loss of air in the cushion can put a person’s bottom on the metal seat instead of being supported above it, Delger said. He said that, ideally, there should be a half-inch of space, but there’s no accurate way of measuring it.

Brad Marsh with Services for Independent Living said gauging whether a cushion is properly inflated is an approximation. A hand is placed underneath the bottom of the user to make sure there’s no contact with the metal seat, and changes are made as necessary. It’s an embarrassing solution and has to be performed several times a day, he said.

“It’s a pretty crude method for adjusting a cushion,” Marsh said.

Marsh provided the idea for the team’s project, one of several he pitches to the capstone course each fall. Part of Services for Independent Living’s business is allowing people to try technologies that could keep them independent at home and in the workplace, Marsh said.

Steve Borgelt, an associate professor at MU who taught the course and served as the team’s adviser, said he solicits ideas from people in the private sector.

“It helps if students are working on a project that’s real,” Borgelt said.

Borgelt said that building a prototype wasn’t a requirement for the course and that most teams stuck to completing a design.

“Everything works on paper,” he said. “Few things work well in real life.”

That’s something Delger found out firsthand. He said that, aside from having to teach himself basic circuitry to work on the project, one of the hardest aspects of the job was tracking down materials for the device.

“We didn’t know where to get things,” Delger said. “You can’t just buy a low pressure gauge.” He said that as the project continued, he found that almost everything he needed was at the hardware store.

Delger said his team came up with two different designs for the prototype. In the device he ended up building, the user would read the pressure gauge and flip a switch to let air out of the cushion or fill it from a tank attached to the wheelchair. The other would have been automatic, with a computer chip monitoring and changing the pressure inside the cushion.

Marsh said that, while he provides the idea and need, he considers whatever the students develop to be their own intellectual property. There are ways to take a prototype to market as a student, he said. Delger, who plans to graduate in May, said that time constraints would make it difficult to continue work and develop the device into a viable commercial technology.


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