First aid
How to use an automated external defibrillator correctly during cardiac arrest.
In a crisis, an automated external defibrillator offers a critical chance to restore rhythm during cardiac arrest, but proper steps, quick action, and calm coordination with bystanders are essential for maximizing survival.
Published by
Steven Wright
March 14, 2026 - 3 min Read
Cardiac arrest demands rapid action, and an automated external defibrillator, or AED, is designed for lay responders. Begin by confirming unresponsiveness and calling for emergency help. If an AED is available, turn it on and follow the voice prompts. No advanced training is required to operate the device; it guides you through each step. While the machine analyzes the heart rhythm, give chest compressions to maintain blood flow unless you are immediately delivering a shock. Clear the scene of bystanders and ensure no one is touching the patient during analysis and shock delivery. Time is life, so act decisively and calmly.
As soon as the AED prompts a shock, ensure everyone is clear of the patient. Shouting “stand clear” is standard to prevent accidental contact. The pads should be placed according to the diagrams on the device: one on the upper right chest, just below the collarbone, and the other on the lower left side of the chest. If a pacemaker or medication patch is present, avoid placing the pad directly over it; offset placement is typically recommended. After pad placement, the AED will analyze again and tell you whether to resume CPR immediately or deliver another shock. Stay focused, maintain rhythm, and use this moment to coordinate with helpers.
Understand timing, pauses, and safe shock guidance for life-saving outcomes.
In the first moments of a potential cardiac arrest, check for responsiveness and breathing. If no response and no normal breathing, shout for help and begin CPR while another bystander retrieves an AED. Opening the airway and delivering compressions at a rate of about 100 to 120 per minute helps sustain vital circulation until defibrillation becomes possible. If an initial responder steps in, assign roles to avoid delays. The AED should be brought to the patient without interrupting chest compressions for more than 10 seconds. This approach maximizes the chances that the device can be used effectively and that circulation is preserved during the critical minutes.
When you power on the AED, it will guide you with clear, progressively spoken instructions. Follow them precisely: attach the pads, confirm proper placement, and allow the device to assess the heart rhythm. Do not touch the patient during assessment. If the rhythm requires a shock, the device will prompt you to clear and deliver. After a shock, immediately resume CPR for about two minutes or until the device instructs otherwise. If no shock is advised, continue CPR until emergency personnel arrive or the patient regains signs of life. Continuous, uninterrupted actions improve the odds of a favorable outcome.
Learn safe pad placement and how devices guide you through rescue.
In public spaces, AEDs are designed for rapid deployment. As soon as you locate the machine, switch it on and follow the voice prompts. Retrieve the pads from their packaging, and look for any barcodes or diagrams that indicate correct placement. Check the patient for signs of consciousness and normal breathing before beginning chest compressions. If the person has a rapid heartbeat but is unresponsive, don’t attempt to analyze too long before applying pads; the device may require immediate defibrillation to restore a normal rhythm. Always ensure a clear environment, and keep bystander interference away from the patient during all steps.
After applying the pads, the AED will analyze the heart rhythm. If a shock is indicated, ensure the area is clear, then press the shock button if the device does not automatically discharge. If no shock is advised, keep performing CPR with a steady cadence. Don’t stop to check for a pulse; continuous compressions are essential. If the person regains responsiveness, monitor breathing and prepare to transition care to medical professionals. AEDs are not a substitute for professional medical care, but they bridge the critical interval until help arrives.
Maintain calm coordination and perform continuous, effective care.
Pad placement varies slightly by model, but the standard approach places one pad on the upper right chest and the other on the lower left side of the chest. If the patient has a medication patch or implanted device, avoid placing the pad directly on top of it by offsetting the pads. Ensure skin is dry and clean before placing pads; if the skin is sweaty, wipe gently. Some AEDs have cables that wrap around the body, so arrange them to avoid tangling with the chest. Verify that the device is fully charged or has batteries functioning properly before an emergency, reducing the risk of device failure during use.
Modern AEDs provide multilingual and accessible instructions, which helps responders of all backgrounds. Speak in a calm, clear voice as you perform CPR and follow the device prompts. If bystanders are unsure about where to stand or how to help, assign tasks like calling emergency services, retrieving the AED, or fetching a bag valve mask to support the process. Keep the scene orderly, cover the patient’s chest if possible to maintain modesty, and avoid crowding around the torso. These measures support efficient cooperation and reduce stress for everyone involved.
Consolidate knowledge with practical, durable guidance for emergencies.
The moment an AED arrives, you should power it on and begin the prescribed sequence immediately. Shocks should be delivered only when the device clearly instructs, and never during chest compressions unless explicitly prompted to pause by the device. If you must interrupt CPR to apply pads or analyze rhythm, resume compressions as soon as possible. The average time to shock in a typical scenario can be just a few precious minutes, so every second matters. Remember to keep the patient’s airway open as you alternate between compressions and device analysis.
Training and regular refreshers improve real-world performance with an AED. Practice scenarios build muscle memory for pad placement, rhythm interpretation, and cadence of chest compressions. If you are responsible for others, designate a coordinator who can oversee the operation and maintain order during a chaotic moment. Even with an AED present, calling emergency services immediately remains critical. The device’s guidance is a complement to trained professionals and does not replace the need for urgent medical intervention.
After the rescue sequence ends, reassess the patient’s status regularly. If the patient becomes conscious and breathing normally, place them in a recovery position and monitor for any deterioration. If the person remains unresponsive, continue CPR until emergency responders arrive or the patient breathes independently again. Don’t remove the pads or let the device be disconnected during transport. When handover occurs, describe the events, rhythm changes, and device prompts to the arriving medical team to ensure continuity of care.
Finally, remember that an AED is a life-saving tool designed for use by bystanders and nonprofessionals. Familiarity with its operation is empowering and can reduce hesitation in critical moments. Keep AEDs readily accessible in workplaces, schools, gyms, and public venues, with regular maintenance checks. Practice with staff drills and ensure that instructions near the device are legible. By understanding the basics and acting decisively, anyone can increase the odds that a stranger’s heart rhythm can be restored and a life saved.
