An AED should be used on someone who has collapsed, is unresponsive, and is not breathing normally (or only gasping) because they may be in sudden cardiac arrest and need a shock as soon as possible to survive.

Quick Scoop: When to Use an AED

Use an AED immediately if:

  • The person suddenly collapses.
  • They do not respond when you talk to them or tap/shake their shoulder.
  • They are not breathing normally: not breathing at all, or only gasping (“agonal” breathing), which is not effective breathing.
  • You cannot find a pulse or you are unsure; lay rescuers are generally told to focus on responsiveness and breathing, not pulse checks.

In that situation:

  1. Call emergency services (or have someone else call).
  1. Start chest-compression CPR right away.
  1. As soon as an AED arrives, turn it on, follow the prompts, and attach the pads while CPR is ongoing as much as possible.

You do not use an AED if the person is awake, responsive, and breathing normally.

Mini “Story” Example

Imagine you’re at the gym and a man in his 50s suddenly collapses on the floor. He doesn’t respond when you shout his name, and his chest isn’t rising like normal; he gives one or two strange gasps and then goes still. Someone calls emergency services while you start hard, fast chest compressions on the center of his chest. Another bystander brings the gym’s AED. You power it on, follow the voice instructions, stick the pads on his bare chest, step back when it tells everyone to stand clear, and deliver a shock when advised. Then you go straight back to compressions until emergency medical help arrives.

That is exactly the type of moment AEDs are made for: sudden collapse, no normal breathing, unresponsive, and every second matters.

Key Facts in Bullet Form

  • AEDs are for sudden cardiac arrest , not for fainting, minor illness, or someone who is awake and talking.
  • They are safe to use by laypeople; they analyze the heart rhythm and will only advise a shock for certain dangerous rhythms like ventricular fibrillation or pulseless ventricular tachycardia.
  • Guidelines emphasize: start CPR immediately on someone unresponsive and not breathing normally, and apply the AED as soon as it is available.
  • Early defibrillation within the first minutes of collapse greatly increases the chance of survival from sudden cardiac arrest.

Simple Timing Rule You Can Remember

  • If the person is:
    • Unresponsive
    • Not breathing normally (or only gasping)
    • Collapse is sudden or unexplained

→ Call emergency services, start CPR, and use the nearest AED right away , following its voice prompts.

Bottom note: This is general information, not a substitute for certified first aid/CPR/AED training. Formal training will give you hands-on practice and local guideline details.

Information gathered from public forums or data available on the internet and portrayed here.