Final answer:
The next step if the person is unresponsive is to check for breathing and initiate CPR if they are not breathing. Remember CPR is critical in these instances and follows specific guidelines for performing chest compressions effectively.
Step-by-step explanation:
If the person is unresponsive and you have already contacted someone for help, the next step is to check for breathing and start CPR if necessary. Administering medication or leaving the person alone is not the correct course of action, nor is performing a detailed physical examination unless you are qualified to do so. With CPR, remember to use the heel of one hand on the sternum between T4 and T9 for chest compressions, to maintain blood flow to vital organs, especially the brain. If the person is choking and conscious, first aid measures such as back slaps or the Heimlich maneuver should be attempted.