-Dr.Dianne McCallister, Chief Medical Officer at Porter Adventist Hospital

Automatic External Defibrillators, or AEDs, have been credited with saving lives in airports, sports fields and even in the workplace and home.

An AED is a computerized device that can deliver a set electrical charge that can shock the heart and disrupt a lethal heart rhythm.

We've used defibrillators for years in cardiac resuscitations. Previous to the AED, it required a trained medical expert who could interpret the heart rhythm to determine whether or not to use the defibrillator.

The AED has an internal program that is able to decipher the electrical rhythm of the heart, determine is a shock is needed, and then deliver it at the appropriate time in the hearts electrical cycle.

It also has a voice prompt system that instructs the user on exactly what to do.

This allows lay people who have a minimal amount of training to use the device and save a life.

The hearts pumping action is driven by an electrical process within the heart.

When the cycle gets out of sync - such as ventricular fibrillation, the heart quivers and does not pump in an organized way and so does not move blood through the body.

By using a defibrillator, either a traditional one that is carried in ambulances and stocked in every part of the hospital, or an AED, we can shock the heart and reset it allowing the normal heart rhythm to recapture the pumping process.

Time is of the essence when a person is in cardiac arrest.

By receiving the training, the average person is able to determine who might need the AED, to give or lead CPR, and is able to quickly use the device without having to read directions or fumble through the appropriate set up.

An article in the journal Circulation describes a study in which two groups of lay responders received training in Basic Life Support.

One of the groups was also trained to use AEDs.

The survival of victims of sudden cardiac death were statistically better in the group that used AEDs compared to traditional life support alone.

This is because the blood circulation is restored and the brain and other vital organs receive all the oxygen they need, which prevents brain or organ damage.

Compared to most medical equipment, these devices are relatively inexpensive - costing in the range of $1500 to $2000.

When AEDs are placed in the community or a business or facility, the American Heart Association strongly encourages that they be part of a defibrillation program in which:

Persons that acquire an AED notify the local EMS office so they can direct responders/callers to the device.

A licensed physician or medical authority provides medical oversight to ensure quality control.

Persons responsible for using the AED are trained in CPR and how to use an AED.

Both the American Heart Association and the American Red Cross offer classes at very nominal costs.

To find an automated external defibrillator class in your area, visit www.americanheart.org or www.redcross.org

Dr. McCallister is on 7NEWS at 11 a.m. every Wednesday. If you have a topic or question you would like her to discuss, email 11am@thedenverchannel.com.