Automated External Defibrillators (AED)

Heart disease is the number 1 killer in the United States. Every day, more than 2600 Americans die from cardiovascular disease, which amounts to 1 death every 33 seconds.

Most of these deaths occur with little or no warning, from a syndrome called sudden cardiac arrest. The most common cause of sudden cardiac arrest is a disturbance in the heart rhythm called ventricular fibrillation.

Ventricular fibrillation is dangerous because it cuts off blood supply to the brain and other vital organs.

• The ventricles are the chambers that pump blood out of the heart and into the blood vessels. This blood supplies oxygen and other nutrients to organs, cells, and other structures.

• If these structures do not receive enough blood, they start to shut down, or fail.

• If blood flow is not restored immediately, permanent brain damage or death is the result.

Ventricular fibrillation often can be treated successfully by applying an electric shock to the chest with a procedure called defibrillation.

• In coronary care units, most people who experience ventricular fibrillation survive, because defibrillation is performed almost immediately.

• The situation is just the opposite when cardiac arrest occurs outside a hospital setting. Unless defibrillation can be performed within the first few minutes after the onset of ventricular fibrillation, the chances for reviving the person (resuscitation) are very poor.

• For every minute that goes by that a person remains in ventricular fibrillation and defibrillation is not provided, the chances of resuscitation drop by almost 10 percent. After 10 minutes, the chances of resuscitating a victim of cardiac arrest are near zero.

Cardiopulmonary resuscitation, usually known as CPR, provides temporary artificial breathing and circulation.

• It can deliver a limited amount of blood and oxygen to the brain until a defibrillator becomes available.

• However, defibrillation is the only effective way to resuscitate a victim of ventricular fibrillation.

CPR is one link in what the American Heart Association calls the Chain of Survival. The Chain of Survival is a series of actions that, when performed together, give the cardiac arrest victim the greatest chance of survival.

• Early access: When an emergency is recognized, the first link in the Chain of Survival is early access. This means activating the emergency medical services, or EMS, system by calling 911. (911 does not work in every community. Be sure to check your local directory, and know the correct emergency telephone number in your community.)
  
  
• CPR: The second link in the Chain of Survival is to perform CPR until a defibrillator becomes available.
  
  
• Early defibrillation: The third and most critical link in the Chain of Survival for a victim of ventricular fibrillation is early defibrillation.
  
  
• Early advanced life support: The last link in the Chain of Survival is early advanced life support. This is provided by experienced medical personnel such as paramedics, nurses, and doctors. Advanced life support includes giving medications and using advanced oxygen delivery techniques to resuscitate a person.

Manual defibrillation, which is the traditional form of defibrillation performed by health care providers, is a complex skill.

• First, the operator must have the ability to interpret ECG (heart) rhythms.
  
  
• The operator also needs to be able to recognize which ECG abnormalities require defibrillation and which ones do not. (For example, a person with a "flat line" ECG would not require, or benefit from, defibrillation.)
  
  
• The operator needs to know how to manually operate the particular model of defibrillator that is available.

Originally, defibrillators were used only in hospitals.

• As the units became more portable, and as early EMS systems began to develop in the United States in the early 1970s, defibrillators began to be used outside the hospital by carefully trained and supervised paramedics.
  
  
• This was a significant step forward in increasing the chance of survival from out-of-hospital cardiac arrest. Rather than transporting the victim to a defibrillator, the defibrillator was transported to the victim.

Because of the delay inherent in getting an ambulance to the cardiac arrest victim within those critical first few minutes, many people continued to die from ventricular fibrillation.

In the mid-1980s, a new generation of computerized defibrillators was introduced. Called Automated External Defibrillators, or "AEDs" for short, these devices were capable of interpreting a person's heart rhythm and automatically delivering a defibrillation shock with only minimal input from the operator.

For the first time, EMS personnel such as basic emergency medical technicians (EMTs) were able to provide the life-saving technique of defibrillation without having to interpret ECG rhythms.

As AEDs began to be placed in more and more "basic life support" ambulances (those not staffed by more advanced paramedics), the survival rates for out-of-hospital cardiac arrest began to rise. However, the problem of getting the defibrillator to the victim in less than 10 minutes remained a challenge.

The next step in reducing the amount of time it took to get a defibrillator to a cardiac arrest victim came with the recognition that the police are often the first to arrive at the scene of a medical emergency, ahead of an EMS unit.

• With this knowledge, some EMS systems began to train and equip police officers to provide defibrillation with AEDs.
  
  
• This allowed defibrillation to be performed sooner, often before an ambulance arrived.
  
  
• The use of AEDs by law enforcement personnel has begun to have a significant impact in resuscitating victims of sudden cardiac arrest.

The evolution of early defibrillation took another major step forward with the concept of public access defibrillation or "PAD."

• It is now recognized that AEDs are extremely easy to use.
  
  
• Formal training programs, such as those offered by the American Heart Association's Heartsaver AED course, can be taught in as little as 4 hours.
  
  
• However, operating an AED is so simple that it can be done successfully even without formal training. Training is recommended for as many people as possible.
  
  
• Local and state regulations determine the training requirements for PAD programs.

The legal requirements that allow the lay public to use AEDs are determined on a state-by-state basis.

• In some states there is true public access defibrillation, meaning that anyone with knowledge of an AED can use one any time it is available. For example, a traveler in an airport may retrieve and use an AED mounted in a public location.
  
  
• In other states, use of AEDs is more restricted. Some states require a formal training program, the direct involvement of an authorizing doctor, or that the AED rescuer be part of a formal in-house response team.
  
  
• In most states, any individual using an AED in a good faith attempt to save the life of a cardiac arrest victim will be covered by some form of a "good Samaritan" statute.

• Regardless of which brand of AED is used, the only knowledge required to operate it is to press the "ON" button.
  
  
• Once the AED is turned on, it actually speaks to you in a computer-generated voice that guides you through the rest of the procedure.
  
  
• You will be prompted to place a set of adhesive electrode pads on the victim's bare chest and, if necessary, to plug in the pads' connector to the AED.
  
  
• The AED will then begin to automatically analyze the person's ECG rhythm to determine if a shock is required. It is critical that no contact be made with the person while the machine is analyzing the ECG. If the person is touched or disturbed, the ECG may not be accurate.
  
  
• If the machine determines that a shock is indicated, it will automatically charge itself and tell you when to press the button that will deliver the shock.
  
  
• Once the shock is delivered, or if no shock is deemed necessary, you will be prompted to check to see if the person has had a return of normal breathing or circulation. If not, you will be reminded to start CPR.

Ventricular fibrillation is common in adults, but it is relatively uncommon in children. Therefore, early AEDs were designed to deliver the amount of electrical current needed by an adult heart.

In certain instances, children can experience ventricular fibrillation.

• Children with congenital heart defects are at risk for rhythm abnormalities such as ventricular fibrillation.
  
  
• Some children go into ventricular fibrillation because of commotio cordis.

Commotio cordis is a syndrome in which a blow to the chest during a relatively brief, specific time period during the heart rhythm cycle can cause ventricular fibrillation.

• This condition was once thought of as a mysterious syndrome of sudden death in young athletes.
  
  
• It is now recognized as a preventable and reversible cause of ventricular fibrillation in children.

The problem with AED use in children is that, unless the child's heart is of a certain size, the amount of current delivered (intended for an adult heart) could actually damage the child's heart and prevent resuscitation.

• The American Heart Association currently recommends that AEDs be used only on children the size of an average 8-year-old or larger.
  
  
• Eventually, AEDs will be capable of determining how much electrical current is required by the particular adult or child being analyzed, and a current just high enough to allow defibrillation will be delivered.
  
  
• In the meantime, one manufacturer has developed an electrode cable that is able to reduce the current delivered by the AED so that it can be used on a child younger than 8 years.

When AEDs were first introduced, they were used predominantly by EMS agencies, and their use was regulated strictly. As more and more states came to realize that AEDs are simple to use, the restrictions became less stringent. Today, many states have true public access defibrillation programs.

With defibrillators becoming more prevalent in communities, and with the greater public awareness of their value, the number of deaths each year from sudden cardiac arrest can be dramatically reduced.

It is hoped that, eventually, AEDs will become as easily available as fire extinguishers: on display everywhere and able to be used by anyone in an emergency.

As it stands today, we are closer than ever to realizing that dream.

• Every day, AEDs are being placed in more and more locations such as airports, on airplanes, and in public buildings and shopping malls.
  
  
• The chances are increasing daily that, some day, you will get to use an AED to save the life of a victim of sudden cardiac arrest.
  
  
• Don't worry, all you have to do is press the "ON" button. The AED will tell you what to do next.

|Web Links|

To obtain information on taking a CPR course, or to receive AED training:

American Heart Association

American Red Cross

Medic First Aid International, Complete emergency care training

Media file 1: This is a heart tracing (ECG) of a person experiencing ventricular fibrillation. Ventricular fibrillation is the most common ECG finding when an adult suffers cardiac arrest.

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Media file 2: Ventricular fibrillation can be successfully treated with defibrillation.

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Media file 3: Minutes count. For every minute that a person in ventricular fibrillation is not defibrillated, the chances of resuscitation drop by almost 10% per minute.

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Media file 4: Cardiopulmonary resuscitation (CPR) can temporarily provide some oxygen to the brain.

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Media file 5: The Chain of Survival involves Early Access to 911, Early CPR, Early Defibrillation, and Early Advanced Life Support.

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Media file 6: Call 911 immediately when an adult is found to be unresponsive.

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Media file 7: CPR buys some time until a defibrillator becomes available.

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Media file 8: Early defibrillation is the most important link in the Chain of Survival.

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Media file 9: Early advanced life support is the last link in the Chain of Survival.

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Media file 10: Manual defibrillators are used by trained health care professionals.

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Media file 11: In the 1970s, portable defibrillators began to be used outside the hospital by many Emergency Medical Services systems.

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Media file 12: Automated external defibrillators allowed defibrillation to be performed with a minimal amount of training.

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Media file 13: The use of AEDs by police units allowed defibrillation to be performed even before the ambulance arrived.

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Media file 14: Ventricular fibrillation victim Julie Lycksell, an operating room nurse, was resuscitated with an AED by Suffolk County, New York Police Officer James Briarton.

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Media file 15: See how easy it is to use an AED.

Media type:  Presentation

Media file 16: One AED manufacturer provides a pediatric electrode cable that allows the AED to be used on children younger than 8 years.

Media type:  Photo

automated external defibrillators, AEDs, cardiopulmonary resuscitation, Chain of Survival, commotio cordis, CPR, defibrillation, electric shock, heart attack, public access defibrillation, sudden cardiac arrest, sudden cardiac death, ventricular fibrillation

1. American Heart Association, International Liaison Committee on Resuscitation. Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Supplement to Circulation. 102. 2000:8.

2. Aufderheide TP, Stapleton ER, Hazinski MF. Heartsaver AED for the Lay Rescuer and First Responder. American Heart Association; 1998.

3. Stapleton ER. AEDs in the School. The Louis J. Acompora Memorial Foundation; 2001.

Author: Joseph Sciammarella, MD, FACP, FACEP, DABMA, Attending Physician, Department of Emergency Medicine, Mercy Medical Center, Rockville Centre, New York.

Editors: James E Keany, MD, FACEP, Director of Emergency Medical Education, Department of Emergency Medicine, Mission Hospital Regional Medical Center and Children's Hospital at Miss; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, ; Jerry Balentine, DO, Professor of Emergency Medicine, New York College of Osteopathic Medicine; Medical Director, Saint Barnabas Hospital.