Automated External Defibrillators (AED)

What is an automated external defibrillator (AED)?

Although advances in emergency cardiac care continue to improve the chances of surviving cardiac arrest, cardiac arrest remains a leading cause of death in many parts of the world.

Each year, almost 350,000 Americans die from heart disease. Half of these will die suddenly, outside of the hospital, because their heart stops beating. 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.
  • However, 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 blood 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.

Chain of Survival

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 in sequence, will give a person having a heart attack the greatest chance of survival.

  • The first link in the chain of survival is immediate recognition of cardiac arrest and activation of the emergency response system by calling 911 (check your community plan, some communities require dialing a different number).
  • The next link in the chain of survival is to perform early CPR, with an emphasis on chest compressions until a defibrillator becomes available.
  • Following early CPR, the next link is to provide rapid defibrillation. In many areas of the country, simple, computerized defibrillators, known as automated external defibrillators, or AEDs, may be available for use by the lay public or first person on the scene.
  • Once the EMS unit arrives, the next link in the chain of survival is effective advanced life support care. This involves administering medications, using special breathing devices, and providing additional defibrillation shocks if needed.

Defibrillation

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

  • First, the operator must have the ability to interpret an electrocardiogram (EKG, ECG) heart rhythms.
  • The operator also needs to be able to recognize what 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.

Automated External Defibrillators

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 had begun to have a significant impact in resuscitating victims of sudden cardiac arrest.

Public Access Defibrillators

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.

How to Operate an Automated External Defibrillator

  • 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.
  • This shock is the same shock that would be delivered be a physician in the emergency department or a paramedic in the ambulance, if the patient were being treated there.
  • Once the shock is delivered you will be prompted to resume CPR.

Automated External Defibrillator Use in Children

Although ventricular fibrillation is more common in adults than in children, it is now recognized that it occurs more frequently in children than was once thought.

For example:

  • 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 (originally intended for the adult heart) could actually damage the child's much smaller heart and prevent resuscitation.
  • If a child is the size of a typical eight-year old, the adult AED protocol is followed.
  • For children older than one year of age but less than the size of an eight-year old, AED manufacturers provide cables capable of reducing the amount of energy that an AED delivers, making it safe to use on the children. When an AED is used on a child, the pediatric cable is used; when an AED is used on an adult (age eight years and older) the adult cable is used.
  • Manual defibrillation is the preferred method of defibrillation in infants, however, if only an AED is available, it is recommended that a pediatric AED cable be used for infant defibrillation.

The Future of Defibrillation

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, in offices, in public buildings, and shopping malls. One of the areas where AEDs have had the greatest effect has been in gambling casinos. This is because of the high security and surveillance; when a victim collapses it is immediately noticed and defibrillation is performed by trained staff in less than one minute.
  • 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.

Automated External Defibrillators (AED) Pictures

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.
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. Click to view larger image.

Ventricular fibrillation can be successfully treated with defibrillation.
Ventricular fibrillation can be successfully treated with defibrillation. Click to view larger image.

Minutes count. For every minute that a person in ventricular fibrillation is not defibrillated, the chances of resuscitation drop by almost 10% per minute. Minutes count. For every minute that a person in ventricular fibrillation is not defibrillated, the chances of resuscitation drop by almost 10% per minute. Click to view larger image.

Cardiopulmonary resuscitation (CPR) can temporarily provide some oxygen to the brain.
Cardiopulmonary resuscitation (CPR) can temporarily provide some oxygen to the brain. Click to view larger image.

The Chain of Survival involves Early Access to 911, Early CPR, Early Defibrillation, and Early Advanced Life Support.
The Chain of Survival involves Early Access to 911, Early CPR, Early Defibrillation, and Early Advanced Life Support. Click to view larger image.

Call 911 immediately when an adult is found to be unresponsive.
Call 911 immediately when an adult is found to be unresponsive. Click to view larger image.

CPR buys some time until a defibrillator becomes available. CPR buys some time until a defibrillator becomes available. Click to view larger image.

Early defibrillation is the most important link in the Chain of Survival. Early defibrillation is the most important link in the Chain of Survival. Click to view larger image.

Early advanced life support is the last link in the Chain of Survival.
Early advanced life support is the last link in the Chain of Survival. Click to view larger image.

Manual defibrillators are used by trained health care professionals.
Manual defibrillators are used by trained health care professionals. Click to view larger image.

In the 1970s, portable defibrillators began to be used outside the hospital by many Emergency Medical Services systems.
In the 1970s, portable defibrillators began to be used outside the hospital by many Emergency Medical Services systems. Click to view larger image.

Automated external defibrillators allowed defibrillation to be performed with a minimal amount of training.
Automated external defibrillators allowed defibrillation to be performed with a minimal amount of training. Click to view larger image.

The use of AEDs by police units allowed defibrillation to be performed even before the ambulance arrived.
The use of AEDs by police units allowed defibrillation to be performed even before the ambulance arrived. Click to view larger image.

Ventricular fibrillation victim Julie Lycksell, an operating room nurse, was resuscitated with an AED by Suffolk County, New York Police Officer James Briarton.
Ventricular fibrillation victim Julie Lycksell, an operating room nurse, was resuscitated with an AED by Suffolk County, New York Police Officer James Briarton. Click to view larger image.

This graph shows asthma consensus guidelines used to manage chronic asthma. These guidelines are also generally used to treat pregnant patients with asthma.
One AED manufacturer provides a pediatric electrode cable that allows the AED to be used on children younger than 8 years. Click to view larger image.

Reviewed on 11/20/2017
Sources: References

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