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Click Here for a demonstration of the Automatic External Defibrillator
Recently, Automatic External Defibrillation (AED) has been receiving much attention in the general public and news media. Although the procedure of defibrillation has been around for decades, it has been reserved for pre-hospital emergency care professionals and physicians. Now through advancements in computer technology the procedure can be safely performed by almost anyone with approximately four hours of training. Through the efforts of the American Heart Association, and other public service agencies, Public Access Defibrillation (PAD) is becoming more commonplace in the U.S. Here we will attempt to provide general information about defibrillation, as well as answer common questions about PAD.
Normal Heart Function
To understand defibrillation it is first important to understand the normal electrical function of the heart. The heart is comprised of four chambers, the two atria on top, and two ventricles on the bottom. Within the right atrium is a specialized group of cells called the sinoatrial node (SA Node). The SA node is the primary pacemaker of the heart forming electrical impulses 60-100 times per minute. These impulses then travel down special pathways in the heart resulting in electrical depolarization of the heart. This rhythm, called normal sinus rhythm, appears on the cardiac monitor as depicted in the picture below. Each "blip" on the rhythm represents the passage of the electrical impulse through the heart. The heart responds to these impulses by contracting and creates the pulses we feel.
Ventricular Fibrillation
Ventricular fibrillation (V-Fib) is an abnormal electrical rhythm in the heart where rather than following the normal electrical pathways described above, the electrical impulses are generated in the ventricles and have no regular pattern. This chaotic electrical activity does not allow the heart to contract, rather the heart "quivers" and as a result is unable to eject blood. This rhythm is the initial rhythm present in 70% of cases of sudden cardiac death.
Defibrillation
Defibrillation is the process of restoring normal electrical activity to the heart. Most people are familiar with this process from TV shows as "shocking" the patient. Although Hollywood is not always accurate in it's depictions of the process, defibrillation is the process of delivering an electrical charge to the heart to stop it from fibrillating. By delivering energy to the heart through electrodes attached to the chest the heart is momentarily stopped allowing the SA Node to again take over as the primary pacemaker of the heart. If the SA Node is again able to resume it's normal function and deliver regular electrical impulses to the heart, rather than the chaotic irregular electrical activity produced by the ventricles, the heart may begin to contract regularly producing pulses in the patient.
What is an AED and how does it work?
An AED is a device used to administer an electric shock through the chest wall to the heart. A microprocessor inside the defibrillator analyzes the victim's heart rhythm through electrodes attached to the patients chest. The defibrillator then determines whether or not defibrillation is indicated based on the rhythm the heart is in. PAD AEDs advise a shock when the patient is in V-Fib.. Dependent upon the make and model of the AED the operator may be required to press specific buttons to analyze the patients rhythm and deliver shocks if needed, or the process may be fully automated. Also audible and/or visual prompts may guide the user through the process depending on the make and model.
What is the difference in an AED and those used by Paramedics and Physicians?
The defibrillators used by Paramedics and Physicians are manual defibrillators, rather than automatic. These devices do not analyze the rhythm the heart is in, instead they only display the rhythm. The Paramedic or Physician then determines whether or not a defibrillation is indicated rather than a microprocessor. In addition to this greater degree of control, manual defibrillators have more capabilities than automatic ones. In addition to defibrillating V-Fib, we can also defibrillate a rhythm called ventricular tachycardia (V-Tach). The reason AED's are generally not able to defibrillate V-Tach is that this particular rhythm may or may not be associated with a pulse. When there is a pulse associated with V-Tach an electrical procedure called synchronized cardioversion is performed rather than defibrillation. Another rhythm in which synchronized cardioversion is performed is Paroxysmal Supraventricular Tachycardia. The final major difference in manual and automatic defibrillators is the ability of the Paramedic or Physician to perform transcutaneous external pacing. It takes years of education and significant training to understand the differences in these rhythms and their treatments, as well as the several other differences between manual and automatic defibrillators, therefore they are beyond the scope of public access defibrillation.
Where can I find an AED?
AED's are becoming more and more commonplace in the general public. They can be found on airliners, sporting arenas, shopping centers, industries, and other areas where there may be large crowds. They are also being placed in police cars, fire department vehicles, and several other governmental vehicles in some municipalities. It is hoped that AED's will become as easily found as a fire extinguisher. GEMS has recently completed training the Gaston County Police Department in the use of AED's. They are now available in all GCPD patrol cars, as well as all Gaston County Rescue Squad units, and most fire trucks in the county.
Why is early defibrillation so important?
Ventricular fibrillation is the initial rhythm in 70% of sudden cardiac death cases. With early defibrillation the patients chances of regaining a normal heart rhythm are dramatically increased. For each minute the patient remains without a pulse their chance of survival decreases by 10%. By having AED's available to the general public with the proper training more people will be able to respond appropriately in the setting of sudden cardiac death.
Who can use an AED?
Most AEDs are designed to be used by non-medical personnel such as police, firefighters, flight attendants, security guards, and other lay rescuers who have been properly trained. Having more people in the community who can respond to a medical emergency by providing defibrillation will greatly increase sudden cardiac arrest survival rates. For information on AED training classes offered by GEMS see our Class Offerings page.
I used an AED and it did not advise me to defibrillate! Why?
Another question that could be asked here is "Why did the Paramedics not defibrillate my loved one?" As stated above, a PAD AED will only defibrillate a patient who's heart rhythm is V-Fib. There are several other rhythms that the heart may be in during sudden cardiac death. These other rhythms do not require electrical therapy, but rather require medications, advanced airway support, and other Advanced Cardiac Life Support (ACLS) procedures from a Paramedic or Physician. Defibrillation does not "jump start" the heart as is often thought. There must be electrical activity already there for it to organize. If there is no electrical activity, or the activity is already correctly organized then defibrillation is not needed. Even though the AED may not advise defibrillation in these situations the provision of CPR prior to the arrival of EMS is critical. CPR circulates blood and oxygen to the patient. Without adequate CPR the chances of ACLS medications being successful are reduced. Actions that must be taken in any type of sudden cardiac death are presented in our AED classes.
Are AED's Safe to use?
An AED is safe to use by anyone who's been trained to operate it. Studies have shown the devices to be able to recognize V-Fib 90% of the time 99% of the time are able to recognize a rhythm that should not be defibrillated. Because of the wide variety of situations in which it will typically be used, the AED is designed with multiple safeguards and warnings before any energy is released. The AED is programmed to deliver a shock only when it has detected VF. The AHA recommends that persons who live or work where an AED is available for use by lay rescuers participate in a Heartsaver AED Course. AEDs are so user-friendly that untrained rescuers may be able to attach the electrodes, press the analyze button (if required), and deliver defibrillations (if indicated). However, untrained rescuers may not know when to use an AED, and they may not use an AED safely, posing some danger of electric shock to themselves and others. Also, untrained rescuers probably would not know how to respond to the victim if the AED prompts "no shock indicated." That is why training is important.
Can I hurt anyone by using an AED?
Another question that could be asked here is, "Can an AED be used as a weapon?" The answer to both questions is "No". The AED will only defibrillate a person who is in V-Fib. If the AED is attached to a person who is not in V-Fib the internal computer will not allow a shock to be delivered. Despite these safety measures however, the AED should never be attached to anyone who has a pulse.
AED's seem easy to use, why do I need training?
Although increased technology have made AED's simple to use proper training is still vital. AED training courses not only address how to use the AED safely,but also when, and when not to use them. The training course will also teach you about the incorporation of the AED in the chain of survival, when to notify EMS, and what actions to take when the AED does and does not indicate defibrillation is necessary. The AED training course will also teach you potential hazards associated with using the AED which will keep you and others around you safe, as well as basic CPR. GEMS strongly encourages everyone to take a CPR/AED training course.
Why do I need to know CPR if I have an AED?
The AED does not take the place of CPR. Where the AED's function is to correct the underlying rhythm when the heart is in V-Fib, CPR's function is to circulate blood and oxygen throughout the body. By continuing this artificial circulation the patient will continue to receive some oxygen which prolongs the window of opportunity for defibrillation and ACLS to work.
How do I purchase an AED?
The Federal Drug Administration (FDA) requires a physicians prescription to purchase an AED. Prescriptions to purchase an AED in North Carolina must be signed by a physician licensed in North Carolina. According to North Carolina state law (G.S. 90-21.15) the seller of any AED in the state must notify the NC Office of EMS AED coordinator within two weeks of the sale. As the purchaser it is also a good idea to notify your local EMS system that you have an AED at your site. Questions regarding the AED reporting requirements can be addressed to the North Carolina Office of EMS at 919-733-2285.
How much does an AED cost and which one should I buy?
Gaston Emergency Medical Services does not recommend any specific brand of AED. There are several manufacturers of AED's, each with specific attributes You can expect to spend about $3,000 for an AED. We recommend you research your decision well before making a purchase decision. More information regarding cost and manufacturers can be found on the North Carolina Department of Administration website, or from any of the manufacturer's websites.
Click Here for a demonstration of the Automatic External Defibrillator