However, he found that he developed severe pain in his knees after around three hours sleeping on his back, due to pressure build up on his kneecaps.
The pain was relieved if Kevin put his leg down flat on the bed and bent it at the knee, but he couldn’t do this with both legs at once because like most people’s, his hip joints wouldn’t turn out that far. Also, he couldn’t alternate his legs between down and up positions because his muscles are too weak to move his legs without assistance.
Kevin lived independently, so there was no-one to help him during the night. His therapist looked into the possibility of a bed that could turn him automatically, but this was prohibitively expensive and may not have suited him.
Kevin had used TAD’s services in the past when he was going sailing, so he asked for a device that would allow him to raise and lower his legs without assistance. Volunteer Peter Bennett, who has a background in electronics, was given this challenging task.
“I started with a blank piece of paper,” Peter said, “and then I did quite a lot of experimentation with different shaped pneumatic cushions, mainly on myself. After about six prototypes I ended up with two cushions on each side to get the right shape.”
To make the cushions, Peter used polyethylene film, of the type used under concrete to seal against moisture, and joined the seams with a heat sealer. Under each of Kevin’s legs there is a larger cushion made from two circles of the film, and a smaller oblong-shaped one that goes underneath the larger one to help it to rotate in the right way to lift the leg.
The cushions were attached at one edge to a strap which goes around the mattress. “Both cushions are joined to the strap at the same place,” Peter said. “The main one blows up and starts to rotate, and as the lower one blows up it pushes the larger one and assists the rotation.”
To inflate and deflate the cushions, Peter used a pump which is normally used to aerate water in an aquarium. “I looked at all sorts of air pumps on the internet,” he said, “and this one seemed good because it is very quiet, which is what you want for the bedroom.”
Peter modified the pump so that it can suck air in as well as blow it out, enabling it to both inflate and deflate the cushions. (It was necessary to have active deflation rather than just letting the cushion go down naturally, to ensure that it is absolutely flat and does not stop Kevin’s leg from lying flat on the bed.) The pump operates continually, with a set of valves which control the direction of the air flow.
Peter also made an electronic controller containing a small microprocessor. This enables Kevin to turn the system on and off and pre-set the sides to alternately inflate and deflate at intervals of anything from six minutes to six hours. He can also manually override the cycle during the night if he gets uncomfortable, and dim the control lights so they don’t bother him when it is dark.
The controller also has a remote, so that Kevin can operate it easily once he is lying in bed and has the ventilator mask on. This is important as he finds it very difficult to move in bed and if he does, he may dislodge the mask and then be unable to put it back on.
A final touch was some fabric covers for the upper cushions. “The plastic is not so comfortable where it touches Kevin’s legs on a hot night, so my good wife Judith made two sets of covers with zips, so they can be easily removed and washed,” Peter said.
Once the system was in place, Kevin’s brother modified it slightly by putting a solid board under the cushions and attaching the straps to that. He found that the cushions raised Kevin’s legs more effectively from a firmer base. “That’s the sort of thing you just wouldn’t know until it was in use,” Peter said.
Kevin says the idea worked exactly as he had thought it would, and was precisely what he needed at the time. “That is the problem with muscular dystrophy, it changes all the time, so you need something that is custom-made specially for you,” he said.
Kevin is very appreciative of the assistance and full of praise for Peter’s efforts. At the conclusion of the project, Kevin’s therapist wrote: “Kevin (and myself ) would like to mention that Peter was great to work with and he was very understanding of Kevin’s needs, listened to all of the feedback that was given and was careful with the way he worked with Kevin.”