Automated External Defibrillators (AED)

AEDs, or automated external defibrillators, are computerized devices that can help prevent death due to sudden cardiac arrest.

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 of 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.

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 the 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.

Manual defibrillation, which is the traditional form of defibrillation performed by healthcare professionals, 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 "flatline" 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 had 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 to 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, the 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 is 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.
• 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.

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.

• 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.

• 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.

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.