Answer:
Determine if an AED (Automated External Defibrillator) is available.
Step-by-step explanation:
A person's heartbeat will stop when the person stops breathing.
Calling for help (calling 911) is the wisest thing to do after which you immediately initiate a CPR (Chest Compressions and Rescue breaths).
This will help in getting oxygen circulate into the person's body.
At this stage, availability of an AED will be very helpful as it can help in restart a heart with an abnormal rhythm. So, one needs to check if there's an AED.