I had several good questions about DNR aka Do Not Resuscitate orders in some classes a few months ago, and recently there has been a very interesting legal discussion on them in one of the Instructors Forums I belong to.
A DNR order is a legal document signed by a patient's physician that states that in the event of a life-ending situation, life-saving measures should not be initiated. This means that CPR is not started. However if someone is choking, and is conscious, you can provide an abdominal or chest thrust to relieve choking. You should not start CPR if the foreign body airway obstruction cannot be removed. You can read the NH Definition of DNR here.
How do you know if a person has a DNR? In a medical care facility this will be in the patients chart and paperwork. The nursing and care staff should be familiar with does and does not have a DNR order. In an out-of-hospital setting check to see the patient is wearing a state-issued DNR bracelet or if the family has a copy of the order.
It varies from state to state, but here in NH where I am located a patient with a terminal condition can receive a DNR bracelet through their physician. It is a state issued bracelet that looks like a hospital bracelet. The NH law on DNR bracelets can be found on the State of NH Website
If you are a Good Samaritan who sees someone collapse and they have a DNR bracelet you do not need to start CPR. HOWEVER - if you're not sure and/or you don't see one. START CPR. These bracelets are more easily recognized by EMS providers.
If you have a loved one at home who has a DNR and you call 911. Please make sure you have a copy of the order to share with EMS providers when they arrive. Tell 911 there is a DNR order as they will relay that to the responding ambulance. That helps them to be prepared and have a treatment plan in place when they arrive.
If you're not in NH take a look at your state's laws and rules on DNR orders and how they may apply to you.