Another option is the hire a home nursing system. They come in shifts. It is expensive.
Do your parents have a long term care policy insurance policy? I know my uncle worked for the post office and didn't know he had a policy which allowed them to use it for my aunti when she could no longer live in their home (with stairs - she had the type of parkinson's where she couldn't walk.
If they are on a limited income, does your state or county have any programs for the elderly?