Final answer:
Biphasic defibrillators send shocks in two directions and are often used in automated external defibrillators (AEDs) which can be operated by laypersons. AED use is crucial in saving lives during cardiac emergencies, especially when used alongside CPR.
Step-by-step explanation:
The type of defibrillator that sends a shock first in one direction and then in the opposite direction is known as a biphasic defibrillator. These devices are characterized by their ability to deliver a large shock of electrical energy that first flows in one direction and then changes to the other, optimizing the likelihood of terminating a dangerous arrhythmia such as ventricular fibrillation. Automated external defibrillators (AEDs) found in many public places might be equipped with this technology. The AEDs are designed to be used by the public and provide verbal instructions for assistance during a cardiac emergency. When coupled with immediate CPR, the correct use of an AED can significantly increase a person's survival chances after a heart attack.