How to lose weight when almost confined to bed?

My mom had heart & lung failure a few years back. She had to have a tracheotomy tube put in and sleeps on a vent machine at night to ist her lungs under her body's weight. She also has degenerative osteoarthritis. If she lost some weight she could lose the tube and probably would feel better, and would at least be able to use the lift bus service with her electric wheelchair. We don't have a lot of money for a weight loss program & our exercise options are limited. Any ideas?