Hierarchy

Do most programs fly nurse nurse or nurse paramedic? I've worked for both and I wasn't sure if it was dictated by the state or if it was local preference. Where I work now youhave to have a medic on board to fly scene calls. How do you settle a dispute re patient care when you have a difference of opinion? Does the nurse over rule the medic or are you two viewed as medical equals (assuming equal experience/number of years etc).