Heart disease is the no. 1 killer in the United States. Every day, more than 2,600 Americans die from cardiovascular disease. That amounts to an average of one death every 33 seconds, most of which occur with little or no warning. Fortunately, for those who go into cardiac arrest on an airplane, every airliner with at least one flight attendant is required to carry an automated external defibrillator as standard emergency medical equipment.

That’s because the most common cause of sudden cardiac arrest is a disturbance in the heart rhythm called ventricular fibrillation. The ventricles are the chambers that pump blood out of the heart and into the blood vessels. Fibrillation is the uncontrolled contraction of the heart muscle. Ventricular fibrillation is dangerous because it cuts off blood supply to the brain and other vital organs. Blood supplies oxygen and other nutrients, and when the blood supply is interrupted, these structures begin to shut down or fail. If blood flow is not restored immediately, permanent brain damage or death is the likely result. Ventricular fibrillation often can be treated successfully by applying an electric shock to the chest. The procedure is called defibrillation. Patients who experience ventricular fibrillation in the hospital usually survive because defibrillation is performed almost immediately.

The outcome differs significantly when cardiac arrest occurs elsewhere. For every minute a person remains in ventricular fibrillation, the chances of successful 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 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.

The Federal Aviation Administration requires every airliner with at least one flight attendant to carry an automated external defibrillator as standard emergency medical equipment. Many carriers, though, installed AEDs on a voluntary basis prior to the FAA regulation.

Qantas was the first airline to install AEDs, and passenger Roland Koenig made history as the first sudden cardiac arrest victim saved in flight. American Airlines installed AEDs on its planes in 1996. Two years later, Mike Tighe of Boston became the first person saved on a domestic flight. In the first two years of the American Airlines AED program, six of 14 sudden cardiac arrest victims, about 40 percent, were resuscitated. This compares with an average survival rate in the United States of just 7 percent. So far, 47 sudden cardiac arrest victims have been resuscitated on American Airlines’ flights, and numerous others have been saved thanks to AED programs initiated by other airlines.

AED placement on commercial aircraft has done more than save lives in flight — it has helped create awareness among the traveling public about the need for rapid access to defibrillation in other settings. A recently published study in the New England Journal of Medicine provides conclusive evidence that laypersons trained to operate AEDs can improve survival rates for out-of-hospital victims.

So, how does any AED work? Modern external defibrillators weigh as little as 4 pounds and are the size of a hardcover novel. Instead of using rechargeable batteries, these AEDs are powered by long-life battery packs. Regardless of which brand of AED is used, operating one is as simple as pressing 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 to plug the pads’ connector into the AED.

The AED will then automatically begin to analyze the person’s heart 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 electrocardiogram. If the victim is touched while the AED is analyzing the cardiac rhythm, 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. Once the shock is delivered, or if no shock is deemed necessary, you will be prompted to check to see if the person has had a return of normal breathing or circulation. If not, you will be reminded to start CPR.

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. A traveler in an airport may retrieve and use an AED mounted in a public location. In most states, some form of a “good Samaritan” statute will cover an individual who uses an AED in a good-faith attempt to save the life of a cardiac arrest victim.

Food and Drug Administration support of AEDs is so strong that the organization recently approved the sale of AEDs without a prescription for in-home use. Eventually, AEDs may be as common as fire extinguishers in private homes — on display and readily available in the event of an emergency. The chances are increasing daily that, some day, you will 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.

For more information about AEDs, visit www.americanheart.org.