If you are TRAINED in pre-hospital care, do you have a legal obligation to lend assistance?
NO
Do you have a moral obligation?
I believe so.
Slight clarification here: I was always taught that once you've been identified as being some sort of trained individual, then you do have the legal responsibility to act.
So, if you have a big Star Of Life on your window, or wear your "Mayville EMS" hat or something, then you actually do need to stop and render aid. A big reason I don't do that much anymore.