What should be done if the patient is unresponsive and not breathing?

When a patient is unresponsive and not breathing, the appropriate and immediate action to take is to perform CPR. This response is grounded in the understanding that the lack of responsiveness and breathing indicates a critical emergency, typically associated with cardiac arrest or a similar life-threatening condition.

Performing CPR serves to circulate blood and oxygen to the brain and other vital organs, which is crucial in minimizing damage due to lack of oxygen. The act of initiating CPR promptly can significantly increase the chances of survival and recovery for the patient. In emergency situations, every second counts, and beginning CPR as soon as possible optimally supports the patient's systemic functions until professional help arrives.

Checking for a pulse may be a step taken in some contexts, but when a patient is unresponsive and not breathing, it's more effective to assume the worst-case scenario and proceed with CPR immediately. Waiting for someone to arrive or tilting the head back does not address the immediate life-threatening issue of lack of breathing and responsiveness. Thus, the best course of action is to perform CPR without delay.