Every minute counts during sudden cardiac arrest. The heart stops pumping blood effectively, and without intervention, brain damage can begin within minutes. An automated external defibrillator (AED) is one of the most powerful tools available to bystanders and trained responders alike. It analyzes the heart's rhythm and delivers a controlled electric shock to restore a normal heartbeat when needed.
The good news is that AEDs are designed to guide users through the process with clear audio and visual prompts, making them accessible even to people without medical training. That said, knowing what to expect before an emergency happens makes a critical difference. Familiarity with the device reduces hesitation, improves response speed, and can mean the difference between life and death.
This guide walks you through exactly how to use an AED device, from the moment you recognize a cardiac emergency to the point when emergency medical services arrive. Whether you are a healthcare professional refreshing your knowledge, an employer preparing your team, a childcare provider, or simply someone who wants to be ready, these steps apply to the vast majority of modern AED models.
Note that while AEDs are designed to be user-friendly, formal hands-on training through a certified program such as a Heartsaver CPR AED course gives you the confidence and muscle memory that reading alone cannot provide. By the end of this guide, you will understand every action required, why each step matters, and how to perform CPR alongside AED use for the best possible outcome.
Step 1: Recognize the Emergency and Call for Help
Before you do anything else, make sure the scene is safe. Look for hazards such as traffic, electrical wires, fire, or standing water. Rushing into a dangerous environment puts you at risk and removes a potential rescuer from the equation entirely. Only approach when you are confident it is safe to do so.
Once you reach the person, tap their shoulders firmly and shout something direct: "Are you okay? Can you hear me?" Do not assume someone is unconscious based on appearance alone. A firm tap and a loud voice give the person a chance to respond if they are simply unresponsive for another reason.
Look for breathing. Absent breathing or abnormal breathing, such as gasping or occasional irregular breaths, is a strong indicator of cardiac arrest. Gasping, sometimes called agonal breathing, is not effective breathing. If you see it, treat the situation as a cardiac emergency and act immediately.
Now here is where many bystanders make a critical mistake. Do not assume someone else has already called 911. Instead, point directly at a specific person nearby and say clearly: "You, in the red jacket, call 911 right now and tell them someone is in cardiac arrest." Assigning the task to a named individual eliminates the bystander effect, where everyone assumes someone else is handling it.
At the same time, send a second bystander to locate and retrieve the nearest AED. In many public spaces, AEDs are mounted in clearly marked cabinets near entrances, hallways, or common areas. Knowing where your nearest AED is located before an emergency occurs is one of the most valuable things you can do today.
Do not wait for the AED to arrive before starting CPR. Every second the heart is not receiving compressions is a second of lost circulation to the brain and vital organs. Start CPR immediately while the AED is on its way.
Success indicator: 911 has been called, someone is actively retrieving the AED, and you have begun chest compressions. You are now in motion, and that matters enormously.
Step 2: Begin CPR While the AED Is Retrieved
CPR is the bridge between cardiac arrest and defibrillation. It keeps oxygenated blood moving to the brain and vital organs, buying critical time until the AED can attempt to restore a normal rhythm. Starting CPR quickly is one of the most impactful actions a bystander can take.
Position the victim flat on their back on a firm, flat surface. A soft surface like a mattress or thick carpet absorbs compression force and reduces effectiveness. If possible, move the person to a harder surface before starting.
Kneel beside the victim and place the heel of your dominant hand on the center of their chest, directly on the lower half of the breastbone. Place your other hand on top, interlacing your fingers. Keep your arms straight and position your shoulders directly above your hands.
According to the American Heart Association's current CPR guidelines, chest compressions for adults should be delivered at a rate of 100 to 120 compressions per minute and at a depth of at least 2 inches. Allow the chest to fully recoil between compressions. Leaning on the chest between compressions prevents the heart from refilling and reduces the effectiveness of each subsequent push.
If you are trained in CPR and willing to provide rescue breaths, use a 30:2 ratio. Deliver 30 chest compressions, then give 2 rescue breaths. Tilt the head back, lift the chin, pinch the nose, and breathe in until you see the chest rise. Each breath should take about one second.
If you are untrained or uncomfortable providing rescue breaths, hands-only CPR is a well-supported alternative endorsed by the American Heart Association. Continuous chest compressions without rescue breaths are significantly better than no action at all. Keep pushing until the AED arrives or until another trained rescuer takes over.
Common pitfall: Many people stop compressions too early or press too lightly. Effective compressions require real effort. You may feel tired within a minute or two. If another bystander is available, rotate every two minutes to maintain compression quality without interruption.
Success indicator: You are delivering consistent, deep compressions at a steady rate. The chest is visibly compressing and recoiling fully with each push.
Step 3: Power On the AED and Prepare the Victim
The moment the AED arrives, open the case. Many modern AED models power on automatically as soon as the lid is opened. Others have a clearly marked power button, often green or prominently labeled. Either way, the device will immediately begin guiding you with audio instructions. Follow those prompts throughout the entire process. The AED is designed to tell you exactly what to do.
While one person operates the AED, a second rescuer should continue CPR without stopping. Coordinating these two tasks simultaneously saves precious time.
Now prepare the victim's chest. Expose the bare skin by removing or cutting away clothing. Many AED kits include a pair of scissors or a clothing cutter for this purpose. Do not place pads over fabric. Direct skin contact is essential for both analysis and shock delivery.
Check if the chest is wet. Moisture from sweat, rain, or water can interfere with pad adhesion and shock delivery. Use the towel or cloth often included in AED kits to quickly dry the chest before applying pads. This step takes only seconds but matters for effectiveness.
Look for any medication patches on the skin, such as nitroglycerin or nicotine patches. Remove them and wipe the area before placing pads. These patches can block pad contact and, in some cases, cause skin burns during shock delivery.
Check for signs of an implanted pacemaker or defibrillator. These devices appear as a small, firm lump under the skin, typically near the upper chest or abdomen. If you notice one, do not place an AED pad directly over it. Position the pad at least one inch away from the implanted device. This is established guidance from AED training programs and ensures the shock is delivered effectively without interfering with the implant.
Finally, if the victim has excessive chest hair and the AED kit includes a razor, use it to shave the pad placement areas quickly. Poor pad contact due to thick hair reduces the device's ability to analyze the heart rhythm and deliver an effective shock. If no razor is available, press the pads down as firmly as possible and proceed.
Success indicator: The AED is on, the chest is bare and dry, and you have addressed any patches, implants, or hair that could affect pad performance.
Step 4: Attach the AED Pads Correctly
Correct pad placement is one of the most important technical steps in the entire process. The pads must be positioned so that the electrical current passes directly through the heart. Incorrect placement reduces the device's ability to read the heart's rhythm accurately and deliver an effective shock.
Remove the adhesive pads from their packaging and peel off the plastic backing. The pads are sticky on one side and will not work if touched repeatedly or contaminated. Handle them by the edges when possible.
Here is the good news: you do not need to memorize placement from scratch. Every AED pad has a diagram printed directly on it showing exactly where it goes. Follow those diagrams. They are clear, visual, and designed for use under stress.
For adult pad placement, position one pad on the upper right chest, just below the collarbone and to the right of the breastbone. Place the second pad on the lower left side of the chest, below the armpit and along the lateral chest wall. This positioning creates a pathway for the electrical current to travel through the heart muscle.
Press each pad firmly against the skin. Run your hand across the entire surface of the pad to eliminate any air pockets. Air gaps between the pad and skin reduce conductivity and can compromise the shock. Take a moment to make sure both pads are fully adhered before moving on.
If the pad cables are not pre-connected to the AED unit, plug them into the connector port now. Most AEDs have a single connector port that is clearly labeled or color-coded. You will typically hear or feel a click when the connection is secure.
For children under 8 years old or under approximately 55 pounds, use pediatric pads if they are available in the kit. Pediatric pads deliver a lower, age-appropriate energy level. If pediatric pads are not available, adult pads can be used with an adjusted placement: one pad on the front of the chest and one pad on the back, between the shoulder blades. This anterior-posterior placement prevents the two adult pads from overlapping on a small chest.
Common pitfall: Placing pads too close together or over clothing significantly reduces effectiveness. Take the extra few seconds to ensure proper placement. The AED may also alert you if it detects a poor connection, so listen for any prompts about pad contact.
Success indicator: Both pads are firmly attached to bare skin in the correct positions, cables are connected, and the AED is ready to analyze.
Step 5: Let the AED Analyze the Heart Rhythm
Once the pads are attached and connected, the AED will prompt everyone to stand clear so it can analyze the heart's electrical activity. This is a critical moment. Stop CPR and make sure no one is touching the victim, not even a hand resting on a leg.
Any physical contact during the analysis phase can interfere with the device's ability to read the heart's rhythm accurately. The AED is detecting very small electrical signals, and outside movement or contact can disrupt that reading. Announce clearly: "Everyone stand clear. Do not touch the patient."
The analysis takes only a few seconds. During that time, the AED is evaluating the heart's electrical activity to determine whether a shockable rhythm is present. The two most common shockable rhythms are ventricular fibrillation and pulseless ventricular tachycardia. These are chaotic or dangerously fast rhythms that prevent the heart from pumping blood effectively but can potentially be corrected with a controlled electrical shock.
After analysis, the AED will announce one of two things. It will either advise that a shock is needed, or it will indicate that no shock is advised. If no shock is advised, resume CPR immediately. This does not mean the person is recovering or that the situation is under control. It means the rhythm detected is not one that responds to defibrillation. CPR remains essential.
Trust the device completely. AEDs are engineered with sophisticated algorithms designed to detect only the specific arrhythmias that respond to defibrillation. They will not recommend a shock when one is not appropriate. Your job is to follow the prompts, keep everyone clear during analysis, and act quickly on whatever the device tells you.
Success indicator: The AED has completed its analysis, no one touched the victim during the process, and you are ready to act on the device's recommendation immediately.
Step 6: Deliver the Shock and Resume CPR
If the AED advises a shock, it will begin charging automatically. You will hear a tone or series of beeps as it reaches the required energy level. This charging process takes only a few seconds, but use that time purposefully.
Before pressing the shock button, perform a visual sweep of the victim. Look left, look right, and confirm that no one is touching the person. Then announce loudly and clearly: "I'm going to shock. Everyone stand clear. Clear!" Make eye contact with bystanders if possible. This is not just a formality. A shock delivered while someone is touching the victim can cause serious injury to that person.
When the AED prompts you and you have confirmed that everyone is clear, press the flashing shock button firmly. The device will deliver the shock. The victim may visibly react with a brief muscle contraction. This is normal.
Now here is one of the most important points in this entire guide: do not pause to check for a pulse after the shock. Resume CPR immediately, starting with chest compressions. The American Heart Association recommends beginning compressions right away rather than waiting, because the heart needs continued support to establish an effective rhythm even if the shock was successful.
Continue CPR for approximately two minutes. The AED will prompt another rhythm analysis at that point. Follow the same process again: stand clear, let the device analyze, and respond to whatever it advises. This cycle of analyze, shock if advised, and resume CPR continues until one of three things happens.
First, emergency medical services arrive and take over care. Second, the victim begins breathing normally and shows clear signs of life, such as movement or responsiveness. If this happens, stop CPR and place the victim in the recovery position, on their side with their head tilted slightly back to keep the airway open. Continue monitoring them closely until EMS arrives. Third, you become physically unable to continue and no one else is available to take over.
Common pitfall: Pausing too long after the shock before resuming CPR is one of the most common errors in AED use. Every second of delay matters. The rhythm of the process should feel almost immediate: shock delivered, hands back on the chest, compressions begun.
Success indicator: The shock was delivered safely with everyone clear, CPR resumed within seconds, and you are continuing the analyze-shock-CPR cycle as directed by the AED.
Putting It All Together: Your AED Readiness Checklist
Here is a quick reference of every step covered in this guide, organized so you can review it at a glance.
Recognize and call: Confirm the scene is safe, check for responsiveness, look for absent or abnormal breathing, call 911, and send someone for the AED.
Start CPR: Begin chest compressions immediately on a firm surface at a rate of 100 to 120 per minute and a depth of at least 2 inches. Add rescue breaths if trained.
Power on the AED: Open the case and follow audio and visual prompts from the moment the device activates.
Prepare the chest: Expose bare skin, dry the chest, remove medication patches, note any implanted devices, and address excessive hair if possible.
Attach pads correctly: Follow the diagrams on the pads for adult or pediatric placement. Press firmly and connect the cables.
Stand clear for analysis: Ensure no one is touching the victim, let the AED analyze, and respond immediately to its recommendation.
Deliver the shock and resume CPR: Confirm everyone is clear, press the shock button, and begin compressions again without delay.
Reading through these steps builds awareness. But hands-on practice builds confidence, and confidence is what allows people to actually act in an emergency. The Heartsaver CPR AED course offered through Midwest CPR Center covers all of these steps in a structured, practice-based format that includes real device simulation and skill evaluation. For employers and organizations, group and corporate training programs give entire teams the ability to respond collectively when seconds count.
Start by locating the nearest AED in your workplace, school, gym, or community today. Knowing where it is before you need it removes one barrier in a moment when every second matters.
Schedule your CPR certification class now and gain the confidence to respond when every second counts.
The Bottom Line on AED Use
Sudden cardiac arrest does not wait for a convenient moment, and neither should your preparation. The six steps in this guide cover everything you need to know about how to use an AED device effectively: recognize the emergency and call for help, begin CPR immediately, power on the AED, prepare the chest and attach pads correctly, stand clear during rhythm analysis, and deliver the shock before resuming CPR without delay.
AED use paired with CPR gives cardiac arrest victims the strongest possible chance of survival. The device guides you through every decision with audio and visual prompts, but the willingness to act, and the muscle memory that comes from practice, is something only hands-on training can provide.
If you are a healthcare professional, the BLS Provider course at Midwest CPR Center gives you the clinical-level training required for your role. If you are an employer, childcare provider, first responder, or community member who wants to be ready, the Heartsaver CPR AED course is the ideal starting point. On-site training options are also available for teams and organizations that want to build a prepared workforce together.
Do not wait until an emergency happens. Equip yourself and your team with life-saving skills today. Schedule your CPR certification class now and take the step that could one day save a life in your community.