Which of the following situations would require the use of an AED?

Using an Automated External Defibrillator (AED) is essential in situations where a person is unresponsive and not breathing. This is indicative of a potential cardiac arrest scenario, where the heart is unable to pump blood effectively, leading to a lack of oxygen in the body. The purpose of the AED is to analyze the heart's rhythm and deliver a shock if a shockable rhythm, like ventricular fibrillation, is detected. This intervention can significantly increase the chances of survival by allowing the heart to re-establish an effective rhythm.

Other situations, such as a person who is breathing normally or has a pulse, do not require the use of an AED. In those cases, the individual may not be experiencing a life-threatening arrhythmia, which is where an AED would be instrumental. Similarly, someone who is responsive and has chest pain would not benefit from an AED at that moment, as they are still breathing and have a pulse, indicating they are not in cardiac arrest. Utilizing an AED in those situations could lead to unnecessary interventions that might cause harm.