Final answer:
Perform CPR for about two minutes before activating emergency services and retrieving an AED when you are alone during a cardiac emergency. AEDs provide instructions for users and help diagnose the patient's heartbeat for proper defibrillation.
Step-by-step explanation:
In a cardiac emergency where you are alone, it is recommended to perform CPR (cardiopulmonary resuscitation) for about two minutes before activating the emergency response system or retrieving an AED (automated external defibrillator) if one was not immediately available. Automated external defibrillators are commonly found in public spaces and are designed for use by the general public, offering verbal instructions and automated diagnosis of the patient's heart rhythm. After two minutes of CPR, if no one else has come to help and you have not already called for emergency services, guidelines call for a break to call 911 (or your local emergency number) and quickly obtain an AED if available.
The exception to this guideline is if the person in need of assistance is an unresponsive infant or child (under puberty) or an adult who suddenly collapses; in these instances, emergency services should be called immediately before administration of CPR or retrieval of an AED. CPR administration cycles should consist of 30 chest compressions followed by two rescue breaths, continuing this cycle until help arrives, an AED is used, or the person begins to show signs of life.