"AED," as previously stated, stands for "Automated External Defibrillator." AEDs are "automated" because they make the decision as to whether a victim needs a shock or not. The machines analyze the victim's heart rhythm and then either deliver the shock automatically or advise a rescuer through voice instructions to deliver a shock by depressing a clearly identified "shock" button. Many AEDs also give vocal step-by-step CPR instructions to assist the rescuer until EMS arrives.

<--Ready light <--On/Off button <--Information button <--Shock button <--Speaker (bottom)

The technology and simplicity of using a modern AED is a far cry from the early days of defibrillation - in a little over two centuries, we've evolved from trial-and-error electrical experimentation on animals to accurate, automated assistance from these small machines. The roots of defibrillation can be traced back over 225 years, when Peter Christian Abildgaard discovered that using electrical impulses on hens made them lifeless. Nearly 75 years later, two scientists named Frederick Ludwig and Albert Hoffa reviewed Abildgaard's findings, and coined a term for the pulseless condition - Ventricular Fibrillation (VF).

Over the next century, more leaps were made in the area of VF treatment, including the successful internal defibrillation of a dog by Jean-Louis Prevost and Frederic Batelli in 1899. But it wasn't until 1947 when this concept was first successfully applied to humans. Dr. Claude Beck, a surgeon from Cleveland, used two internal paddles to directly shock the heart of a 14-year-old boy during surgery.

In 1956, Paul Zoll was the first to perform a successful external defibrillation with paddles placed across the chest. Defibrillation therapy grew in popularity - in the next decade, it became available in most operating rooms across the country. In the 70's, three doctors began work on a portable, automatic defibrillator prototype, and by 1979, the AED was officially introduced for clinical use.

So although AEDs have been around for more than 25 years, only recently has improved technology and greater acceptance allowed them to become widespread. Early units were expensive, bulky, and used rechargeable batteries that were difficult to maintain. Today, the AED has evolved into a lightweight (most are less than five pounds), effective device with longer-lasting batteries (The battery for Philips Heartstart Onsite AED, for example, will last up to four years in standby mode). Plus, as demand for them increases, the prices are dropping all the time. A typical AED nowadays might cost the same as a good radar unit or laptop computer.

Not all AEDs are the same, however. Though all are designed for ease of use and have the same basic attributes, each brand has varying looks, styles, and features. Some of the more well-known AEDs include those by Philips, Zoll, Cardiac Science, and Medtronic. Research these brands and others to see what style would best suit you and your department.

Learn even more about AEDs and Sudden Cardiac Arrest. Continue on or click any of the links below to go directly to that topic.