What Does a Defibrillator Do?

What is a Defibrillator?

Before we can answer “what does a defibrillator do?”, let’s first define what a defibrillator is. A defibrillator is a device that sends electric shocks or pulses to the heart – think about the machines that doctors use in television shows when they yell “clear!” However, defibrillators come in many different shapes, sizes, and forms. Some defibrillators can be implanted in a person (ICDs); some can be worn on the body (WCDs); some are linked up to complicated machines in hospitals; some come in colorful cases mounted on library and school walls (AEDs). Now that we understand what a defibrillator is, let’s take a look at why we need them.

The Purpose of Defibrillation

Defibrillation refers to the act of sending an electric pulse to the heart (via a defibrillator) and can be used to target a handful of issues. Heartbeat is regulated by something in the heart called the sinoatrial (SA) node, or the “pacemaker.” When the pacemaker stops working – causing the heart to beat too fast, too slow, or to stop beating all together – a defibrillator is needed to restore a normal heartbeat.

These heart conditions, referred to generally as arrhythmias, can have many different causes. Having a heart attack, congenital heart defect, high blood pressure, diabetes, stress, and more can all predispose a person to arrhythmias. AEDs are used specifically to treat sudden cardiac arrest (SCA), when the heart stops, but we will cover more on that later.

How Does a Defibrillator Work?

Defibrillators shock the heart to restore normal rhythm, but how do they work? All defibrillators have some form of sensor which detects heartbeat and arrhythmias. These sensors are either placed directly on the chest (contained within AED pads) or rest right on the heart within an implanted defibrillator. Medical professionals then review this data and decide how big of a shock to deliver using manual defibrillators. These devices use electrodes that must be charged and placed on the chest to deliver the electric pulses.

What Does an AED Do?

For those of us without extensive medical training, automatic defibrillators have built-in technology to assess the victim’s heartbeat and select the appropriate shock level. In instances of sudden cardiac arrest, the combination of well-delivered CPR and a shock from an AED is the key to improving the victim’s chance of survival. But how does an AED work? Most devices offer visual or verbal instructions to help you place the electrodes on the victim’s chest, making them easy to use for any bystander. From there, the device will detect the heartbeat and, if it determines that a shock is needed, will automatically charge itself and either deliver the shock right then, or prompt the user to press a button.

Next Steps

Now that you know what a manual defibrillator and AED do and how they both work, we hope you’ll be more informed and prepared to act in the event of a cardiac emergency. If you want to learn more, consider signing up for an AED certification class or reach out to our customer service team with any questions.


Written by BlaireWritten by Blaire Czarniecki

Customer Service Director

Blaire attended the University of Tennessee where she graduated with a Bachelor of Science in Human Ecology- Child and Family Studies. She has been in the Automated External Defibrillator (AED) industry for over eight years and is the Director of Customer Service for Coro Medical. Blaire is also an American Red Cross-certified CPR/AED/First Aid Instructor, highly trained by each manufacturer on their specific AEDs, and knowledgeable regarding ALL State AED regulations and legislation.“I know that every day I come to work, I am playing a part in saving someone’s life. I am passionate about these devices and am always looking for new and innovative ways to spread awareness and knowledge about Sudden Cardiac Arrest (SCA). I look forward to the day when everywhere I go, I will see an AED—when SCA will no longer take any lives.”

Last updated September 14, 2021.