Volunteering

I haven't come across any programs where medically schooled professionals are volunteering. Now, that doesn't mean it doesn't exists, of course.
I'd suggest to talk to either your primary doctor (or the assistant). They should be able to get your wife started.

I would suggest she approach pharmacies. Many of them have nurses and para-medical professionals to provide services and might be very receptive to a volunteer who can provide services to the community.

She would definitely have my confidence. Good luck.

This organization seeks volunteers to help Seniors at three locations in Puerto Rico:

http://www.nationalchurchresidences.org/