Free Guide to AED Safety and Use Information

What Is an Automated External Defibrillator and How Does It Work

An Automated External Defibrillator, commonly called an AED, is a portable medical device that can restart a person's heart if it stops beating effectively. The device analyzes the heart's electrical activity and, when needed, delivers an electric shock to restore a normal heartbeat. AEDs are designed to be used by people without medical training, making them valuable tools in public spaces, workplaces, schools, and homes.

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When a person experiences sudden cardiac arrest, their heart may enter a dangerous rhythm called ventricular fibrillation or pulseless ventricular tachycardia. In these conditions, the heart quivers ineffectively instead of pumping blood throughout the body. This stops oxygen from reaching the brain and other vital organs. An AED works by delivering a measured electric shock, called defibrillation, that can reset the heart's electrical system and allow it to resume normal beating.

The science behind AEDs involves understanding heart rhythms. A normal heart beats 60 to 100 times per minute in a coordinated pattern controlled by electrical signals. During cardiac arrest, these signals become chaotic. The AED's computer analyzes the heart rhythm through adhesive pads placed on the person's chest. If the device detects a rhythm that can be corrected with a shock, it will instruct the user to deliver one. Many modern AEDs are fully automatic, meaning they deliver the shock without requiring the user to press a button.

According to the American Heart Association, using an AED within the first few minutes of sudden cardiac arrest dramatically improves survival chances. For every minute that passes without defibrillation, the survival rate drops by approximately 7 to 10 percent. Research shows that when AEDs are used within the first three minutes, survival rates can reach 50 to 70 percent. This underscores why having AEDs readily available in community settings is critical.

Practical takeaway: Learn where AEDs are located in places you frequent regularly, such as your workplace, gym, or local shopping center. Knowing their locations means you can direct someone to retrieve an AED quickly if a cardiac emergency occurs.

Recognizing When Someone Needs an AED

Identifying when someone may be experiencing sudden cardiac arrest is the first step toward using an AED effectively. Cardiac arrest happens when the heart stops beating or beats so ineffectively that it cannot pump blood to the body. A person in cardiac arrest will be unresponsive—they will not answer questions or react to stimulation. They will also not be breathing normally or will have no breathing at all.

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The signs of sudden cardiac arrest develop rapidly and are distinct from other medical emergencies. When someone collapses and does not respond to your voice or touch, check if they are breathing. Place your ear close to their mouth and nose and watch their chest. If there is no normal breathing or only occasional gasping, and the person does not respond, treat it as a potential cardiac arrest situation. Do not waste time trying to determine the exact cause of unconsciousness—call emergency services immediately and retrieve an AED.

Cardiac arrest differs from a heart attack, which is a common source of confusion. A heart attack occurs when blood flow to the heart muscle is blocked, usually by a blood clot. A person having a heart attack may experience chest pain, shortness of breath, and discomfort in the arm or jaw. They remain conscious and aware. Cardiac arrest, by contrast, causes immediate loss of consciousness and breathing. A heart attack can lead to cardiac arrest if not treated, but they are separate conditions. Both require emergency care, but the presence of unconsciousness and absent breathing indicates the need for an AED.

Certain situations put people at higher risk for cardiac arrest. According to the Centers for Disease Control and Prevention, about 356,500 out-of-hospital cardiac arrests occur in the United States each year. Cardiac arrest can happen to anyone, at any age, though it is more common in adults over 45. Risk factors include a personal or family history of heart disease, previous heart attacks, high cholesterol, high blood pressure, diabetes, smoking, and obesity. However, cardiac arrest can strike even young, healthy individuals, particularly during or immediately after strenuous physical activity.

Practical takeaway: If you see someone collapse or find someone unresponsive and not breathing normally, immediately call 911 and retrieve the nearest AED. Do not delay—even a few seconds matter in cardiac emergencies.

Step-by-Step Instructions for Using an AED

Using an AED involves straightforward steps that anyone can follow, even without prior training. The device itself provides voice prompts that guide you through the process. Most AED use can be summarized in six key steps: recognize the emergency, call emergency services, retrieve the AED, prepare the victim's skin, attach the pads, and follow the device's instructions.

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First, confirm unresponsiveness and absent breathing, then immediately call 911. Do not delay this step—professional help is essential. While someone calls emergency services or if you are alone, retrieve the nearest AED. Many public AEDs are stored in wall-mounted cabinets marked with a white heart and lightning bolt symbol. Once you have the AED, return to the person and open the device. Most AEDs have a lid or cover that opens to reveal the control panel and adhesive pads.

Next, prepare the person's chest. If the person is wearing clothing, quickly remove it to expose the chest. If the chest is wet, quickly dry it. If the person has excessive chest hair and you have access to the small razor sometimes included in AED kits, quickly shave the area where the pads will go, but do not delay treatment to do this thoroughly. Turn on the AED—some models turn on automatically when opened, while others have a power button. Once powered on, the device will begin giving voice instructions.

The AED will instruct you to attach the pads. There are two adhesive electrode pads that stick to the skin. The first pad typically goes on the right side of the chest, below the collarbone. The second pad goes on the left side of the chest, on the rib cage, several inches below the armpit. Follow the diagrams printed on the pads if unsure. Press firmly to ensure good contact with the skin. If the person is a child under 8 years old or weighs less than 55 pounds, use pediatric pads if available, or follow your AED's instructions for pediatric mode.

Once the pads are attached, the AED will analyze the heart rhythm. During this time, make sure no one is touching the person. The AED will tell you whether a shock is needed. If a shock is indicated, the device will say "Shock advised" or similar wording. If the AED is semi-automatic, you will need to press the shock button. If it is fully automatic, it will deliver the shock on its own. After the shock, the AED will instruct you to resume cardiopulmonary resuscitation (CPR) or will tell you the shock is not indicated and CPR should continue.

Practical takeaway: Practice locating and opening an AED before an emergency occurs. Familiarize yourself with the device's appearance and operation so you can act confidently if needed.

Understanding AED Pad Placement and Safety Considerations

Proper pad placement is essential for an AED to work effectively. Incorrect placement can reduce the effectiveness of the device or cause skin burns. The standard pad placement, called anterolateral placement, positions one pad on the right anterior chest wall below the collarbone and the second pad on the left side of the chest at the midaxillary line (the imaginary line running down from the armpit).

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Each AED pad has a diagram printed on it showing correct placement. The pads should be placed on bare skin. If the person has chest hair, this can interfere with pad contact. Ideally, hair should be removed, but this should never delay treatment. Some AED kits include a small razor for this purpose, but using it should only take a few seconds. If the person has a pacemaker or implantable cardioverter defibrillator (ICD), place the pads at least one inch away from the device's location, which appears as a small lump under the skin.

Safety considerations when using an AED include ensuring no one is touching the person when the device is analyzing or delivering a shock. Water and moisture can interfere with pad contact and conduct electricity. If the person is in water, move them out