If I had a dollar for every time a dermatologist or podiatrist tried to be 'helpful' on an emergency scene... I could probably buy a coffee at Starbucks... The same goes for 'nurses.' If an ER nurse wants to help out, that's great. Invariably though, it's a nurse at a nursing home or dialysis center...
I don't mean to imply these folks aren't skilled professionals, but prehospital medical emergencies are generally well outside their experience, and the confusion that arises from that can be dangerous.