When someone experiences sudden cardiac arrest, every second matters. Using an Automated External Defibrillator (AED) as quickly as possible can significantly improve the chances of survival. One of the most important moments during a rescue is when the AED begins analyzing the person’s heart rhythm. According to the American Heart Association (AHA) and the International Liaison Committee on Resuscitation (ILCOR), rescuers must immediately stop CPR and ensure no one is touching the person.
They should then follow the AED’s voice prompts so the device can accurately determine whether a shock is needed. Many people mistakenly believe they should continue chest compressions or touch the victim while the AED is analyzing. However, even slight movement can interfere with rhythm analysis and delay treatment, reducing the effectiveness of the rescue.
This blog explains exactly what to do while an AED is analyzing, why these steps are essential, common mistakes to avoid, and what to do once the analysis is complete so you can respond with confidence during a cardiac emergency.
What Does It Mean When an AED Is Analyzing?
When an AED announces, “Analyzing heart rhythm. Do not touch the patient,” it is assessing the heart’s electrical activity to determine whether a defibrillation shock is needed. According to the American Heart Association (AHA), no one should touch the person during this brief analysis because movement can interfere with the AED’s ability to accurately evaluate the heart rhythm.
The AED determines whether the person has a shockable rhythm, such as:
- Ventricular Fibrillation (VF)
- Pulseless Ventricular Tachycardia (pVT)
If the AED detects a shockable rhythm, it will advise delivering a shock. If no shock is advised, it will instruct rescuers to resume high-quality CPR immediately. Although the analysis usually lasts only a few seconds, it is a critical step that helps ensure the person receives the appropriate treatment as quickly as possible.
What Should You Do While the AED Is Analyzing?
The moments while an AED is analyzing are critical to a successful rescue. Following the correct steps recommended by the American Heart Association (AHA) and ILCOR helps the AED accurately assess the heart rhythm, prevents unnecessary delays, and ensures the person receives the appropriate treatment as quickly as possible.
Follow these essential steps to help ensure the AED accurately analyzes the heart rhythm and provides the appropriate treatment recommendation:
1. Stop CPR as Soon as the AED Begins Analyzing
When the AED announces that it is analyzing the heart rhythm, immediately stop chest compressions. According to the American Heart Association guidelines, movement from CPR can interfere with the AED’s ability to accurately analyze the heart’s electrical activity. Pause CPR only when the AED instructs you to do so, and be prepared to resume high-quality CPR immediately after the analysis if directed.
2. Ensure No One Is Touching the Person
Once the AED begins analyzing the heart rhythm, make sure everyone stays clear of the person. This includes rescuers, bystanders, and anyone nearby. Even slight movement or physical contact can interfere with the AED’s ability to accurately assess the heart rhythm. Before the analysis begins, clearly announce, “Clear! Nobody touch the patient,” and visually confirm that no one is touching the person until the AED completes its analysis.
3. Stay Calm and Follow the AED's Voice Instructions
AEDs are designed to be easy to use, even for people with little or no emergency response training. Stay calm, listen carefully, and follow each voice instruction exactly as it is given. The device will guide you through every step of the rescue and tell you what to do next.
Common AED voice prompts include:
- Analyzing heart rhythm
- Do not touch the patient
- Shock advised
- No shock advised
- Begin CPR
Following these prompts promptly and accurately helps the AED analyze the heart rhythm correctly and ensures the person receives the appropriate care without unnecessary delays.
4. Check for Safety Hazards
While the AED is analyzing the heart rhythm, take a moment to quickly assess the surrounding area. A safe environment helps ensure the AED functions properly and reduces the risk of injury during the rescue.
Make sure that:
- No one is touching the person
- The surrounding area is safe for rescuers and bystanders
- There is no standing water or excessive moisture around the person
- Any oxygen source is moved away before a shock is delivered, if possible
- The AED pads are securely attached to the person’s bare chest
Taking these simple safety precautions helps the rescue process continue safely and without unnecessary interruptions.
5. Be Prepared for the AED's Next Instruction
The AED analyzes the heart rhythm in just a few seconds. Once the analysis is complete, it will either advise delivering a shock or instruct you to resume CPR. Listen carefully to the voice prompts and act immediately, as every second is critical during a cardiac arrest.
5.1 If a Shock Is Advised
If the AED detects a shockable heart rhythm, it will either charge automatically or instruct you to press the shock button. Before delivering the shock, make sure the area is safe and that no one is touching the person. This helps prevent injury and allows the shock to be delivered safely.
Before delivering the shock:
- Ensure everyone is clear of the person
- Visually confirm that no one is touching the person or any equipment connected to them
- Clearly announce, “Clear!” so everyone knows to stay back
- Press the shock button only when the AED instructs you to do so
After the shock is delivered, immediately resume high-quality CPR when prompted by the AED. Continue following the device’s voice instructions until emergency medical services (EMS) arrive, the person shows clear signs of life, or the AED provides further directions.
5.2 If No Shock Is Advised
If the AED determines that a shock is not needed, it does not mean the emergency is over. According to the American Heart Association (AHA), you should immediately resume high-quality CPR while leaving the AED turned on and the pads attached. Continue following the AED’s voice prompts, as it will keep monitoring the person’s heart rhythm and provide further instructions.
After the AED announces “No shock advised,” take the following steps:
- Leave the AED pads securely attached to the person’s bare chest
- Resume high-quality CPR immediately without unnecessary interruptions
- Continue following the AED’s voice instructions throughout the rescue
- Allow the AED to reanalyze the heart rhythm after about two minutes of CPR or whenever prompted
Continue CPR and AED use until emergency medical services (EMS) take over, the person begins showing clear signs of life, or the AED provides new instructions. Even when a shock is not advised, continuous CPR and ongoing rhythm analysis remain essential parts of effective cardiac arrest care.
Why Must Nobody Touch the Person During AED Analysis?
During the analysis phase, the AED measures the heart’s electrical activity to determine whether a defibrillation shock is needed. According to the American Heart Association (AHA), even slight movement or physical contact can interfere with this process by creating electrical interference, known as an artifact. This can affect the AED’s ability to accurately analyze the heart rhythm and may delay lifesaving treatment.
Touching the person during AED analysis can:
- Delay the delivery of the appropriate treatment
- Interfere with accurate heart rhythm analysis
- Cause unnecessary interruptions in CPR
- Reduce the overall effectiveness of the resuscitation effort
To help ensure the AED provides an accurate treatment recommendation, make sure everyone stays clear of the person until the device completes its analysis or instructs you to continue.
What Common Mistakes Should You Avoid While an AED Is Analyzing?
Even small mistakes during AED analysis can delay treatment or affect the device’s accuracy. Following American Heart Association (AHA) recommendations helps ensure the AED analyzes the heart rhythm correctly and supports effective cardiac arrest care.
The following are the most common mistakes to avoid while an AED is analyzing the heart rhythm:
1. Continuing CPR During AED Analysis
According to the American Heart Association (AHA), stop chest compressions only when the AED instructs you to analyze the heart rhythm or deliver a shock. Continuing CPR during analysis can interfere with rhythm detection. Resume high-quality CPR as soon as the AED instructs you.
2. Touching the Person During Rhythm Analysis
Keep everyone away from the person while the AED is analyzing the heart rhythm. Even slight movement or physical contact can interfere with the AED’s analysis and delay the appropriate treatment recommendation.
3. Ignoring the AED's Voice Instructions
Listen carefully to every voice prompt throughout the rescue. The AED provides clear, step-by-step instructions to help you respond correctly and reduce unnecessary delays during a cardiac emergency.
4. Removing the AED Pads Too Early
Leave the AED pads securely attached to the person’s bare chest throughout the rescue. Removing them too soon prevents the AED from continuously monitoring the heart rhythm and delivering additional treatment if needed.
5. Delaying CPR After AED Analysis
If the AED announces “No shock advised,” immediately resume high-quality CPR, as recommended by the AHA. Prompt chest compressions help maintain blood flow to the brain and other vital organs until the AED performs another rhythm analysis or EMS arrives.
What Are the Key Tips for Effective AED Use?
Following the correct steps during AED use can improve the chances of survival during sudden cardiac arrest. Quick action, proper CPR, and careful attention to the AED’s instructions help ensure the person receives effective care until professional help arrives.
To improve the chances of survival during a cardiac emergency:
- Activate Emergency Medical Services (EMS) immediately
- Begin High-Quality CPR without delay
- Activate the AED as soon as it is available
- Follow all AED voice prompts carefully
- Maintain a clear area during rhythm analysis
- Resume CPR immediately when directed by the AED
- Continue resuscitation efforts until professional help arrives
Using an AED effectively requires quick action, proper CPR, and careful attention to the device’s instructions. Following these steps helps maintain continuous care, supports accurate rhythm assessment, and improves the overall response during a cardiac emergency.
How Can You Be Prepared to Use an AED During an Emergency?
An AED is designed to guide rescuers through a sudden cardiac emergency, but knowing the correct steps before an emergency occurs can make a meaningful difference. Understanding when to pause CPR, keep everyone clear, follow the device’s instructions, and resume care helps ensure effective AED use.
Quick action, proper CPR, and confidence in using an AED can support a better response during cardiac arrest. Learning these skills in advance helps you provide timely assistance and support the person until emergency medical professionals arrive.
Every second counts during a cardiac emergency. At CPR VAM Training Center, learn how to use an AED and perform life-saving CPR with confidence through BLS, ACLS, PALS, Heartsaver® CPR AED, and Heartsaver® First Aid CPR AED training. Gain hands-on experience, practice real-life response skills, and be prepared to act when every moment matters.
FAQs
1. Why is it Important to Stay Calm When Using an AED During an Emergency?
Staying calm helps you follow the AED instructions correctly and avoid unnecessary delays during a cardiac emergency. Modern AEDs are designed to guide users step by step, even if they have limited emergency response experience. Remaining focused allows you to provide safer and more effective care while waiting for professional help.
2. How Does an AED Decide Whether a Person Needs a Shock?
An AED checks the heart’s electrical activity to identify whether a shockable rhythm is present. The device analyzes the rhythm and provides clear instructions based on its findings. Following the AED’s prompts helps ensure the correct action is taken at the right time.
3. What Should You Check Before Using an AED on Someone?
Before using an AED, make sure the environment is safe and that emergency services have been contacted. The person’s chest should be accessible so the AED pads can be placed correctly, and everyone should stay clear when the device is analyzing. These safety steps help the AED work properly and support an effective rescue effort.
4. Can CPR and AED Use Be Performed Together During Cardiac Arrest?
Yes. CPR and AED use work together as important parts of cardiac arrest response. CPR helps maintain blood flow, while an AED evaluates the heart rhythm and provides a shock when appropriate. Knowing when to continue CPR and when to pause for AED analysis is an essential part of effective emergency training.
5. Why Should AED Pads Remain Attached After a Shock or No-Shock Decision?
AED pads should remain attached because the device may need to continue monitoring the heart rhythm and provide further instructions. Removing the pads too early can interrupt the rescue process and delay additional treatment if needed. Keeping the AED connected allows continuous guidance until emergency responders arrive.
