Final answer:
Onsite adults should call 911 in case of sudden cardiac arrest but wait for qualified medical professionals to apply the AED.
Step-by-step explanation:
When adults suspect sudden cardiac arrest, it is important for them to call 911 immediately, as this is a medical emergency that requires immediate professional assistance. However, they should wait until qualified medical professionals arrive to apply the Automated External Defibrillator (AED).
An AED is a portable electronic device that delivers an electrical shock to a person's heart to correct abnormal heart rhythm. Lay persons can use AEDs as they are designed to automatically diagnose the patient's heart condition and then apply the shock with appropriate energy and waveform. However, it is recommended to perform CPR (cardiopulmonary resuscitation) before using the AED in many cases.