Under what circumstances should an AED be used?

An AED, or Automated External Defibrillator, should be used specifically when a person is unresponsive and not breathing. This condition typically indicates a cardiac arrest, where the heart has stopped beating effectively. In such situations, immediate use of an AED can significantly increase the chances of survival by delivering a shock to the heart, which may restore a normal rhythm.

Using an AED is not appropriate when a person is breathing normally, as this suggests that the heart is still functioning, and a defibrillator is not required. Similarly, if the heart is still pumping blood, the use of an AED is unnecessary and could cause harm rather than help. Bystanders being unsure of what to do is not a reason for using an AED; however, it's important to remember that AEDs are designed to provide spoken instructions to guide users through the process, even if they are not trained. Therefore, the presence of unresponsiveness and lack of breathing is the critical factor warranting AED use.