I am not an attorney and I don't play one on the Internet. Nothing I write is ever legal advice.

My understanding is that in most, if not all, US States, medical professionals have a duty to provide care if they witness someone in life-threatening medical distress. If it was in fact a nurse and the nurse didn't provide CPR when it was called for, the nurse could easily lose his or her license.

In many US States there is a Good Samaritan Law that immunizes you against liability if you act within the scope of your training to help someone who might otherwise die. If you're certified for CPR or following the 911 dispatcher's directions, you cannot be held liable for performing CPR in those states.

I would never knowingly step foot in a facility that had a "no CPR" policy.