Illustration of an anatomical heart glowing red

How can an AED save someone’s life?

Written on February 22, 2023 by Gillian (Gigi) Singer, MPH. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Table of contents

What is a defibrillator?

A defibrillator is a medical device used to deliver an electric shock to the heart in order to restore its normal rhythm in cases of cardiac arrest. Cardiac arrest is a condition in which the heart suddenly stops beating normally, leading to a lack of blood flow to the brain and other vital organs.

Defibrillators are important in the management of cardiac arrest and can be life-saving when used promptly and appropriately.

What is an automatic external defibrillator (AED)?

Per the American Heart Association, “An automated external defibrillator (AED) is a lightweight, portable device that delivers an electric shock through the chest to the heart. The shock can potentially stop an irregular heartbeat (arrhythmia) and allow a normal rhythm to resume following sudden cardiac arrest (SCA). SCA occurs when the heart malfunctions and stops beating unexpectedly. If not treated within minutes, it quickly leads to death.”

Essentially, AEDs are user-friendly defibrillation devices that can be used in emergency situations by non-medical personnel. Anyone who is trained in CPR can use an AED.

Other types of defibrillators

There are also implantable defibrillators, which are placed inside the patient’s chest and are used to monitor the heart’s rhythm and deliver shocks as needed to prevent sudden cardiac arrest. These devices are typically used in patients who are at high risk for cardiac arrest due to a history of heart disease or other risk factors.

When to use an AED

AEDs are used in cases of sudden cardiac arrest (SCA), which “is the leading cause of death in the United States,” according to Avive, “taking the lives of over 350,000 people per year” [1]. About 90% of the sudden cardiac arrests that happen outside of a hospital are fatal [1].

Sudden cardiac arrests are incredibly common. In fact, “1 in 25 US high schools can expect to have an SCA event each year” [1].

Where you can find an AED

AEDs are usually found in offices, gyms, health clubs, places of worship, schools, etc. Health outcomes are significantly improved when AEDs are in public places like these, as shown by the following statistics provided by Avive [1]:

  • “Victims of cardiac arrest in gyms & health clubs with an AED have a 93% chance of survival versus a 9% chance when no AED is present.”
  • “Research shows that over 50% of people who attend religious services at least once a week are over the age of 50, indicating that the vast majority of people at faith-based organizations are at higher risk of SCA. AEDs need to be readily accessible at faith-based organizations.”
  • “Approximately 70% of SCAs occur in the home or place of residence, where AEDs are rarely available.”

How to use an AED on an adult

Avive published the following directions on how to use an AED on an adult [2]:

  1. Recognize cardiac arrest and call 911
  2. Perform CPR
  3. Turn on the AED and follow the directions given by the AED’s audio
  4. Expose the person’s bare chest, including their bra
  5. Apply the electrode pads to the person’s dry skin
  6. Allow the AED to analyze the person’s heart rhythm
  7. Make sure no one touches the person as the AED delivers a defibrillation shock
  8. The AED will instruct you when it is safe to continue hands-only CPR after the shock has been delivered. The AED may also determine that a shock is not needed, depending on if it is a semi-automatic model or a fully-automatic model
  9. Perform CPR and re-analyze. AEDs are programmed with the American Heart Association’s guidelines. The current AHA protocols call for two minutes of CPR in between AED heart rhythm analysis periods. Follow the AED instructions about when to resume CPR and when to deliver additional shocks

How to use an AED on a child

The primary differences between using an AED on an adult and a child are the size of the electrode pads and the level of energy of the shocks that are administered. Additionally, the placement of electrodes is different for kids compared to adults.

Avive published the following directions on how to use an AED on a kid: “Depending on an AED’s make and model, the attenuation might be pre-set into a separate set of pediatric electrode pads, built for the sole and exclusive use of pediatric patients, or it might be built into the AED and activated using a button, ‘key,’ or another switching mechanism [2].”

  • If your AED requires a separate set of electrodes, you will need to install the child pads during the emergency, power on the AED, and listen to the voice prompts just like you would for an adult patient.
  • If your AED allows you to use the same pads for adult and pediatric patients, you only need to press the button to change the device to child or pediatric mode on your AED.

After using an AED

Because you called 911 prior to administering CPR and using the AED, emergency medical services will take over when they arrive, but until then, you should continue CPR and shock administration as the AED prescribes. It’s easy to get quickly exhausted while in this situation, so call for another bystander’s help.

AED laws

Legally, there are protections provided to you when you use an AED to try and help someone.

According to AEDUS, the federal Cardiac Arrest Survival Act provides “limited immunity from civil liability to a person who uses or attempts to use an AED on a victim of a perceived medical emergency… all 50 states and the District of Columbia now include AED usage as part of their Good Samaritan laws” [3].

Where can you get AED training?

The American Heart Association offers CPR and AED training through training centers. To find a training center you can call 1-888-AHA-4CPR or you may also visit to search by your ZIP code [4].

You can check in on your heart with the Everlywell Heart Health Test, which measures cholesterol, hs-CRP (inflammation marker), and HbA1c.

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  1. Sudden cardiac arrest facts. Avive AED. URL. Published January 16, 2023. Accessed February 20, 2023.
  2. How to use an AED: Step-by-step guide. Avive AED. URL. Published January 18, 2023. Accessed February 20, 2023.
  3. AED defibrillator legislation - AED resources. AED.US. URL. Accessed February 20, 2023.
  4. What is an automated external defibrillator? - American Heart Association. URL. Accessed February 20, 2023.
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