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Automated External Defibrillators

Introduction

Each year nearly 500,000 people die from sudden cardiac arrest. Preventing death caused by sudden cardiac arrest requires fast action and a critical sequence of events: early activation of the EMS system (calling 9-1-1), early CPR, early defibrillation and early advanced care at a medical facility. Administering CPR techniques and dialing 9-1-1 have been the way to respond to a cardiac arrest in previous years, but the use of AEDs (automated external defibrillators) is relatively new.

Traditionally, only highly-trained individuals in hospitals or EMS personnel used manual defibrillators. But technology has now made it possible for non-medical personnel to perform defibrillation in non-medical settings. AEDs equipped with an internal computer can interpret the heart rhythm to determine if a victim is in ventricular fibrillation (V-fib), a potentially fatal heart rhythm. If V-fib is indeed occurring, the unit instructs the user to press an activation button which causes defibrillation.

Operation

In a healthy heart, a natural “pacemaker” delivers organized electrical impulses that generate a steady repeating rhythm. When the heart goes into cardiac arrest, random electrical impulses come from many locations within the heart, simultaneously causing an uneven heart rhythm. This uneven rhythm does not allow the chambers of the heart to fill and pump blood properly through the body. To restore a normal heart-beat, a defibrillator delivers a shock to the heart— momentarily stopping it—which interrupts the electrical chaos and helps restore a normal heartbeat.

Various AEDs operate in a similar manner. A pair of electrode pads are connected to the unit and the unit is activated. After a brief automatic internal check, the user can place the pads on the victim’s bare chest. The AEDs diagnostics determine whether defibrillation is required. If defibrillation is required, the unit instructs the user to clear the area around the victim and press an activation button. The unit will then instruct the user to immediately begin CPR. After 2 minutes the unit will perform another analysis to see if defibrillation is needed again.

Audible and/or visual prompts guide the user through the entire process so the possibility of error is very small. Studies of the units indicate that AEDs are capable of detecting V-fib and recommending a shock 90% of the time, and recommending not to shock 99% of the time when not required. With this accuracy, an AED has a greater ability to diagnose V-fib than does an emergency response team.

The AED delivers approximately a 3000-volt charge in less than 1/1000 of a second. That is enough electricity to light a 100-watt bulb for 2–3 seconds. In cases when the heart is in full cardiac arrest with no sign of V-fib, only medications can restore heart movement.

CPR is also required since an AED only restores a heart’s normal beating pattern to a heart in V-fib. Rescue breathing and chest compressions are needed to supply oxygen to the victim if breathing and heart-beats are not occurring. After the prescribed sets of breaths/compressions, the unit will analyze the motionless victim and determine if a shock is necessary.

During treatment, the AED records the data it detects on the patients condition. Some models can also record a live audio of the incident. This data can be transferred to the physician treating the patient when he/she arrives at the hospital.

Training

Manufacturers of AEDs recommend users undergo training which normally takes several hours. The defibrillators are so easy to use that most untrained users will be able to attach the pads, allow the unit to analyze and provide shocks. However, users must still be taught when to use the AED, how to respond if a shock is not required and how to operate an AED safely.

Company Risk Factors

Before the advent of AEDs, 95% of sudden cardiac arrest victims died—even with first aid, rescue breathing and cardio-pulmonary resuscitation. In contrast, defibrillation delivered within the first minutes saves the lives of up to 75% of cardiac arrest victims. Many large facilities such as airports, sports stadiums and large workplaces are installing AEDs to increase the chance of saving lives.

In order to evaluate whether your facility would benefit from an AED, consider the following:

• How many people are at your site? Large numbers of people increase the likelihood that an AED would need to be used.
• What is the response time of the local emergency response service to get to the furthest place on your site? Traffic conditions, elevators, stairs, gates all can cost valuable time to negotiate. 
• What type of workforce or visitor demographics does your facility encounter? Consider the health, age, fitness and stress levels of the people. 
• Are workplace hazards present such as electrical or confined spaces? Electrical shock or asphyxiation could induce heart fibrillation. 
• Is the facility in a remote area? Can an emergency response team reach these areas in time? 
• Does your facility have an emergency response team already in place? If these teams are needed, it’s a good bet an AED would some day be used.

AED Programs

An AED program is a natural extension of an existing first aid program. After purchasing a unit, you should contact your local hospital emergency dept. and consult with a physician. The physician is responsible for establishing appropriate policies and procedures for the use of the device. Specific requirements do vary from state to state so it’s important to discuss details with your AED supplier, physician or local American Heart Association/American Red Cross chapter. Generally, programs contain the following topics:

• Periodic training and evaluation of the user on AED use, first aid and CPR 
• Notifying the local EMS service of it’s presence and meeting their requirements 
• Maintenance and regular testing of the AED according to manufacturer guidelines 
• When emergency care is rendered to activate the EMS system 
• Bloodborne Pathogen training may also be required

AED Resources

American Heart Association (www.americanheart.org) 
American Red Cross (www.redcross.org) 
Public Access Defibrillation League (www.padl.org) 
American Association of Occupational Health Nurses (www.aaohn.org) 
American College of Emergency Physicians (www.acep.org) 
International Medical Consulting (www.medicalconsulting.net/docs/PADLaws.html)

Click here for PowerHeart® AED.

Click here for PowerHeart® AED trainer.

Commonly Asked Questions

References

Automatic External Defibrillators: Do You Need an AED?, Lesley Young, Occupational Health and Safety Canada, March 2000, pp.62-66. 

AEDs: Starting a Company Program, Karen Sarkis, Occupational Hazards, April 2000, pp.61-64. 

American Heart Association

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