When Is An AED Supposed to be Used In CPR?

When Is an AED Used in CPR? Understanding Automated External Defibrillators

An Automated External Defibrillator (AED) is a life-saving device designed to deliver an electric shock to the heart in cases of sudden cardiac arrest (SCA). The use of an AED in conjunction with cardiopulmonary resuscitation (CPR) significantly increases the chances of survival for individuals experiencing cardiac arrest. In this comprehensive guide, we will explore when an AED is used in CPR, how AEDs work, the importance of their timely deployment, and the steps to effectively use an AED during a life-threatening emergency.

The Role of an AED in CPR

Cardiopulmonary resuscitation (CPR) is a crucial first aid technique used to maintain blood circulation and provide oxygen to vital organs when a person experiences cardiac arrest or respiratory failure. While high-quality CPR is essential in these situations, it may not be sufficient to restart the heart's normal rhythm. This is where an AED comes into play.

An AED is a portable device that can analyze the heart's rhythm and deliver an electric shock, known as defibrillation, to restore a normal heartbeat. The key role of an AED in CPR is to identify specific life-threatening arrhythmias, such as ventricular fibrillation or ventricular tachycardia, and deliver a shock to reset the heart's electrical activity.

When Is an AED Used in CPR?

1. In Cases of Cardiac Arrest

The primary scenario in which an AED is used in CPR is when a person experiences sudden cardiac arrest (SCA). SCA occurs when the heart's electrical system malfunctions, leading to a chaotic and ineffective heart rhythm. During SCA, the heart may quiver or beat too rapidly to effectively pump blood, causing the victim to lose consciousness and stop breathing.

Signs of Cardiac Arrest:

  • Unresponsiveness: The victim does not respond when tapped or spoken to.
  • Absence of Normal Breathing: The victim is not breathing or is gasping for air (agonal breathing).
  • Lack of Pulse: The rescuer cannot detect a pulse.

In cases of cardiac arrest, the AED plays a critical role in assessing the heart's rhythm and delivering a shock if a shockable rhythm is detected.

2. As a Part of the Chain of Survival

The use of an AED is a vital component of the Chain of Survival, a sequence of actions aimed at increasing the chances of survival for individuals experiencing sudden cardiac arrest. The Chain of Survival typically includes the following key links:

a. Early Recognition and Activation

Recognizing the signs of cardiac arrest and immediately activating the emergency response system (calling 911 or the local emergency number) is the first link in the Chain of Survival.

b. Early CPR

Initiating high-quality CPR as soon as possible after recognizing cardiac arrest is crucial to maintain blood circulation and oxygen delivery to vital organs.

c. Early Defibrillation

The third link in the Chain of Survival is early defibrillation, which involves the timely use of an AED. The sooner defibrillation occurs, the higher the chances of successful resuscitation.

d. Advanced Life Support

Professional medical help, including advanced life support measures, is the final link in the Chain of Survival. Paramedics and healthcare providers can provide advanced care, including medications and advanced airway management.

How AEDs Work

AEDs are designed to be user-friendly, making them accessible to individuals with minimal or no medical training. Here's how AEDs work:

1. Automated Voice Prompts

When an AED is turned on, it provides automated voice prompts that guide the user through the steps of using the device. These prompts are designed to be clear and concise, making it easy for rescuers to follow instructions even in high-stress situations.

2. Electrode Placement

The AED typically comes with adhesive electrode pads with illustrations showing their proper placement on the victim's chest. These pads contain sensors that allow the AED to monitor the heart's rhythm.

3. Heart Rhythm Analysis

After the electrode pads are attached to the victim's chest, the AED begins analyzing the heart's rhythm. During this phase, it assesses whether a shockable rhythm (ventricular fibrillation or ventricular tachycardia) is present.

4. Shock Delivery

If the AED detects a shockable rhythm, it will instruct the rescuer to stand clear and not touch the victim while it delivers a shock. The shock is intended to reset the heart's electrical activity and allow it to resume a normal rhythm.

5. CPR Guidance

In addition to rhythm analysis and shock delivery, many AEDs also provide real-time CPR guidance. They may prompt the rescuer to resume CPR after a shock or guide them on the depth and rate of chest compressions.

Steps to Use an AED During CPR

Using an AED effectively during CPR involves the following steps:

1. Assess the Scene

Before approaching the victim, assess the scene for potential dangers or hazards. Ensure that the area is safe for you and the victim.

2. Check for Responsiveness

Gently tap the victim and shout loudly to assess their responsiveness. If they do not respond, proceed immediately to the next steps.

3. Call for Help

In cases of cardiac arrest, call 911 (or the local emergency number) to request professional medical assistance. If someone else is present, instruct them to call for help. If you are alone, perform CPR for about two minutes before calling for help, if possible.

4. Retrieve the AED

Locate the nearest AED and retrieve it. Many public places, such as airports, schools, and malls, have AEDs installed in accessible locations.

5. Turn On the AED

Power on the AED to begin the automated voice prompts.

6. Attach Electrode Pads

Follow the illustrations on the electrode pads to correctly place them on the victim's chest. Ensure that the pads adhere securely.

7. Allow the AED to Analyze

Once the electrode pads are attached, allow the AED to analyze the victim's heart rhythm. Make sure no one is touching the victim during this analysis.

8. Follow AED Prompts

Listen carefully to the AED's voice prompts. If it advises delivering a shock, ensure that everyone is clear of the victim, and press the shock button if required.

9. Resume CPR

After delivering a shock, the AED may prompt you to resume CPR. Follow the AED's instructions on the depth and rate of chest compressions.

10. Continue CPR and Follow AED Prompts

Continue the cycle of CPR and follow any additional prompts provided by the AED until professional medical help arrives, the victim shows signs of life, or you are too fatigued to continue.


The use of an Automated External Defibrillator (AED) in CPR is a critical component of the Chain of Survival and can significantly improve the chances of survival for individuals experiencing sudden cardiac arrest. AEDs are designed to be user-friendly and provide clear voice prompts to guide rescuers through the process of delivering life-saving shocks.

Understanding when to use an AED and how to use it effectively can make a substantial difference in emergency situations. Proper training in CPR and AED use is essential for individuals and communities to respond confidently and competently when every second counts. By recognizing the importance of AEDs in CPR, we can contribute to safer environments and increase the chances of saving lives during life-threatening cardiac emergencies.

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