What is AED? What is an AED?

AED stands for “Automated External Defibrillator” and is sometimes written as automated external defibrillator AED, AED machine, AED unit, AED device, etc.. An AED is a medical device used in case of sudden cardiac arrest (SCA) to give life-saving aid to the victim. AED machines link a pre-programmed computer to a unique user interface and special electrical pads. They are made to be highly portable and designed for use in quick response to an SCA emergency. AEDs are capable of guiding any rescuer to give: 1) cardiopulmonary resuscitation (CPR), and 2) heart-rhythm correcting, life-saving shock(s) to victims, wherever they may have succumbed.

Invention of the AED

Automated external defibrillators (AEDs) have been growing in use ever since their invention in 1965 by decorated Irish military doctor and future cardiologist Frank Pantridge. It had become accepted that most deaths from cardiac arrest occurred when the heart lost its normal beating rhythm and went into abnormal ventricular fibrillation (VF) or ventricular tachycardia (VT).

Ventricular fibrillation is the abnormal heart rhythm most often responsible for sudden cardiac arrest. It is characterized by a rapid but irregular heartbeat.

Ventricular tachycardia is also a heart rhythm disorder (arrhythmia), caused by abnormal electrical signals in the lower chambers of the heart (ventricles). If it continues, this regular, but extremely rapid beating can keep the heart from filling with blood.

Note: Neither ventricular fibrillation or ventricular tachycardia are considered heart disease. Heart attacks and Sudden Cardiac Arrest are heart issues with different underlying causes.

With either ventricular fibrillation or ventricular tachycardia, the heart stops pumping blood through the body, but with an electric shock from an AED that heart’s false rhythm can briefly be fully stopped. This allows the heart’s own built-in electrical pacemaker to again stimulate a regular heartbeat. Believing that the needed shock should be applied as soon as possible at the site of the heart attack, Prof Pantridge led development of the world’s first portable defibrillator. He and colleagues John Geddes and technician Alfred Mawhinney rigged a car battery and electrode pads to create a portable device for delivering the needed shock.

Modern Automated Defibrillators

AEDs now consist of four main parts:

  • Processor (with user interface)–guides the user in attaching pads to victim and providing CPR; delivers shocks as needed; records event details.


  • Battery–long life medical quality power source to perform self-checks, operate processor, and provide shocks when needed in SCA event.


  • Capacitor–electrical component which stores and releases battery energy in the process of delivering shocks.


  • Electrode pads–wired pads attached to skin of SCA victim for detection of heart rhythm and delivery of shocks as needed. Some are capable of guiding proper CPR efforts of rescuer.


There are now many manufacturers of AEDs in the US: 

  • Cardiac Science–Cardiac Science, Inc, was formed in 1991 to develop FDA-approved rhythm-analysis software, the foundation for the first fully automatic bedside defibrillator. The Powerheart defibrillator was able to treat life-threatening arrhythmias without the need for human intervention.

  • Defibtech AED–Headquartered in Guilford, Conn., all of Defibtech’s life-saving products are conceived and developed in-house and are designed and built in the United States at state-of-the-art facilities. Owned by a leading international medical device manufacturer, Nihon Kohden, Defibtech is committed to designing and creating products that help communities around the world respond to sudden cardiac arrest. 

  • HeartSine–HeartSine was founded in 1998 to continue innovative development of advanced lifesaving products for the treatment of sudden cardiac arrest. Their passion to innovate began in 1967, when they invented the first mobile defibrillator and changed th way the world delivered emergency care.

  • Philips Healthcare AEDs–Philips launched its first public access AED, Forerunner by Heartstream, in 1996 and set the pace in the industry with milestones and innovation breakthroughs, such as its pediatric capability, throughout its history. Philips created AEDs for the layperson to use when faced with an extraordinary moment–giving an untrained responder the confidence to act both quickly and decisively and lead the way to save a life.

  • Physio-Control AEDsPhysio-Control Corporation was founded in 1955 by Dr. Karl William Edmark as a pioneering company in the field of portable defibrillation. Physio-Control manufactured and distributed emergency defibrillation and automated CPR medical equipment. The company was most recently acquired in 2016 by Stryker Corporation and is now part of Stryker’s Emergency Care division.

  • ZOLL AEDs–Based on cardiac research stemming back to 1952, the ZOLL company was begun in 1980 by Dr Paul M Zoll and associates. Zoll was the first physician to successfully use external defibrillation to regulate heart rhythms in patients. With products for defibrillation and cardiac monitoring, circulation enhancement and CPR feedback, supersaturated oxygen therapy, data management, ventilation, and therapeutic temperature management, ZOLL provides a comprehensive set of technologies that help clinicians, EMS and fire professionals, as well as lay rescuers, improve patient outcomes in critical cardiopulmonary conditions.

Why AEDs are Needed

In the fifty years since the first AED was invented they have become sophisticated machines, increasing in portability, ruggedness, versatility and user friendliness. Their development has been driven by the ever-present, time-sensitive, life-and-death nature of SCA events.

According to the American Heart Association (AHA) over 350,000 times a year in the United States alone, victims of all ages succumb to heart arrhythmia (sudden cardiac arrest). At any time and in any location a person may collapse without warning, stop breathing, lose consciousness and have no pulse. If not treated immediately, a victim of sudden cardiac arrest may die within a matter of minutes due to loss of blood flow to the brain.  Because of this very short span of time between collapse and likely death, it is crucial that AEDs be available for deployment immediately along with CPR (cardiopulmonary resuscitation). 

A present-day AED guides a rescuer to perform CPR and place special electrical pads onto a cardiac arrest victim’s body. Sensing the function of the victim’s heart, it then administers heart stabilizing shocks to literally bring the victim back to life!

Because AEDs are needed immediately in case of SCA, they have become widespread in their use in virtually every setting, not only in hospitals but also in public, commercial, and even home settings. The developing rules, programs, policies and guidance around AEDs is referred to as public access defibrillation or PAD.

Who can use an AED?

Because of the need for an instant on-site response to a sudden cardiac arrest, AED technology and laws regarding their use have been purposely developed so that virtually anyone, even a child, can put them to use in an emergency situation. While there are very sophisticated forms of the AED which are typically deployed by emergency medical personnel with advanced knowledge and training in treating heart attacks, there are also very simple versions for use by any bystander. Thus it is most important that public awareness be aroused as to the existence of these machines, the circumstances in which they should be used, and the need to have AEDs accessible in every possible setting.

The significance of AEDs in guarding public health has led to the adoption of laws by various states of the U.S. This began officially in 1997 with Florida, and as of 2010 all 50 states have since enacted laws and/or regulations regarding defibrillator use. All this is in the hope of increasing the chances of survival for an SCA victim.

States are working to:

  • make AEDs more available,
  • normalize public AED use,
  • encourage AED training,
  • require that maintenance and testing meet manufacturers’ standards,
  • create a registry of defibrillator locations,
  • establish a “Good Samaritan” exemption from liability,
  • and determine more detailed requirements for AED certification and registration.


How to Operate an AED

“Today’s AEDs couldn’t be easier to use – you open the box and the device talks you through the steps – yet, despite this, people are still hesitant to intervene when they witness someone experiencing a sudden cardiac arrest episode,” said Dr. Joe Frassica, chief medical and innovation officer, Philips and chief science officer, Philips Research North America.

Knowing the signs of cardiac arrest is the first step in deciding an AED is needed. Following are guidelines from the Mayo Clinic for responding to a possible cardiac arrest.  

If you see that someone has fainted and suspect that he or she may need an AED, you should:

  1. Check to see if the person is breathing and has a pulse.
  2. If you cannot feel a pulse and the person is not breathing, call for emergency help. If there are other people present, one person should call 911 while the other prepares the AED. If you’re alone, call 911 or emergency services first to make sure help is on the way. ADDED NOTE: Time is of the essence; do not be afraid to move quickly, approach anyone, speak loudly and clearly, and announce that you are seeking an AED! AEDs in public places are normally kept in wall-mounted cases similar to fire extinguishers.
  3. Turn on the AED. The automated external defibrillator will give you step-by-step voice instructions explaining how to check for breathing and a pulse and how to position electrode pads on the person’s chest.
  4. Deliver the shock. When the pads are in place, the AED automatically measures the person’s heart rhythm and determines if a shock is needed. If it is, the machine tells the user to stand back and push a button to deliver the shock. The AED is programmed not to deliver a shock if a shock isn’t needed.
  5. Administer CPR. Start CPR after the shock is delivered if CPR is still needed. The AED will also guide users through CPR. The process can be repeated as needed until emergency crews take over.


American Red Cross Video

To see a public use AED in action first-hand, view this Red Cross instructional video below. There are many such videos available on youtube.com and you can most likely find one showing the exact brand and model you may have in your own workplace, school, etc.


As shown in the Red Cross video, CPR, or “cardiopulmonary resuscitation” is typically associated with use of an AED in case of cardiac arrest. CPR is an emergency procedure that employs chest compressions to keep blood flowing through the body in case of a heart attack, especially to the brain. It should immediately be done if a patient is:

  • unresponsive
  • unconscious
  • not breathing
  • has no pulse

You can review important CPR guidelines here.

[NOTE: If a victim definitely has a pulse, but is not breathing or is struggling to breathe, artificial respiration without CPR should be used.]

Once begun, CPR continues while the AED is started and the AED pads then attached to the subject. The ultimate goal of CPR plus AED is to restore normal heartbeat and breathing. As stated above, it should be continued until trained emergency medical personnel arrive and take over rescue efforts. (SEE AMERICAN RED CROSS VIDEO, ABOVE).

Features of Newer AEDs

The fact is, according to the American Heart Association, “CPR plus early defibrillation can more than double the rate of survival from out-of-hospital cardiac arrest”. – 2015 AHA Guidelines  Because of the importance of pairing CPR and AED use together in responding to an SCA event, newer AEDs have been designed with features to facilitate the proper combination of quality CPR and defibrillating shock from an AED.

Led in development by the Zoll Medical Corporation, AEDs now provide comprehensive assistance to those responding to SCA. These features are numerous and come in different forms and combinations depending on the brand of AED. They include, among others:

  • Self-testing/reporting features to assure machine readiness
  • 5-year batteries
  • heavy duty design and casing
  • Audio-visual prompts and graphics to guide the first-aider
  • Switchable language for both audio and video
  • Fool-proof electronics preventing unneeded shocks
  • Simplified controls and fully automatic shocking
  • Special wires and pads which assure proper placement
  • Automatic shock adjustment for pediatric victims
  • Sensors providing real-time feedback re: CPR compression depth and rate
  • ECG Readout
  • Event recording/transmission memory device


The Public Needs to be Aware and AED Trained

While public AEDs can be used by most anyone, training in first aid/CPR/AED practices is highly recommended. It is beneficial to all for us to gain knowledge and skills that we can use as lay bystanders in a medical crisis. The confidence gained through training makes the one trying to save a life much more able to proceed quickly and properly in any emergency. It is especially important in case of SCA, a life-and-death scenario where giving the right first aid is crucial and time is of the essence.

How much does an AED Cost?

How much does an AED Cost? A new AED will typically cost between $1,200 and $3,000. Be sure to read our “How much does an AED Cost?” article to learn more about what impacts AED machine cost, how much used AEDs cost and much more.

AED Survivor Stories

The following stories were taken from the sca-aware.org website and provide a unique look into the importance and impact of these life saving devices.


I am not the same person I was before October 10, 2020…I was out at a farm, two hours from home, arriving at the pumpkin patch when out of nowhere my chest and left arm went into excruciating pain. My husband called 911, and I was taken to a hospital…two hours from home. The ER decided to keep me overnight for testing and evaluation since there was some damage to the heart muscle, and while moving me onto a different floor; I went into sudden cardiac arrest, received CPR and AED, and was put on a ventilator in a drug induced coma for 12 hours. I remember nothing past the time in the ER to waking up after the ventilator was pulled out and…feeling the pain of broken ribs. I ended up staying four days in the ICU, and as of December 9, 2020, I have an internal defibrillator, surgically implanted to watch over and guard my heart.No neurological or brain damage.


On Tuesday, February 12, 2019 at approximately 3:40 in the afternoon, I was at work, not in my office but in the main hallway…I was talking to a member of my team, when I started to get dizzy. I started to stumble around and then ran forward straight into a door frame. I fell to the floor and several team members came and stood around. One team member went to get my boss. I tried to tell them what to do, but could not talk…My boss’s office was next to mine and they are detached from everything else. When I saw him come through the double doors into the hallway, i knew everything would be okay. I then closed my eyes. They came back and he immediately said get the AED. He said he talked to me the whole time because he heard that helps bring people back. The AED said to deliver a shock and he pushed the button and after the shock, started a round of CPR…


On May 23rd, 2015 I was running alongside my brother in the Soldier Field 10 mile race. It was a perfect weather day and I felt great. Six miles into the race along Lake Michigan I suddenly felt a “thump” in my chest that felt very unusual. I stepped off the race path into the grass. I clearly remember getting light headed and dizzy, but not feeling any pain. I bent over putting my hands on my knees and then…lights out…I had a sudden cardiac arrest and needed CPR and AED to save my life. I later learned that a physician (who requested to remain anonymous, so I have never been able to thank him) just happened to be also running in the race and started CPR on me immediately. I also fell just feet away from the aid station that had an AED onsite. I read the 10% survivor statistics and think about how lucky I am to still be here.

Leave a Reply

Your email address will not be published. Required fields are marked *