Which of the following devices is used to correct life-threatening cardiac arrhythmias?

The Automated External Defibrillator (AED) is specifically designed to correct life-threatening cardiac arrhythmias, such as ventricular fibrillation or pulseless ventricular tachycardia. It analyzes the heart's rhythm and can deliver an electric shock if necessary to restore a normal rhythm. This capability is crucial in emergency situations where a person's heart is not effectively pumping blood due to these dangerous arrhythmias.

In contrast, other options do not serve the same purpose. A CPR machine assists in performing cardiopulmonary resuscitation, which is a life-saving technique but does not specifically address arrhythmias in the manner that an AED does. A ventilator is used to provide artificial ventilation to patients who cannot breathe on their own, and while it is a critical device in respiratory support, it doesn't correct cardiac arrhythmias. An ambulance is a mode of transport for patients to emergency care but doesn’t treat arrhythmias directly. Therefore, the AED stands out as the device that is directly involved in correcting life-threatening cardiac arrhythmias.