Teaching Colleagues and the General Public about Automatic External Defibrillators

Estelle Beaumont, RN, PhD

Prog Cardiovasc Nurs. 2001;16(1) 

In This Article

Types of Defibrillators

When teaching others about AEDs, it is important to explain the three main types of defibrillators that currently exist. For basic life support, the AED is most often used. Another type of external defibrillator is categorized as semiautomatic and has manual overrides and various settings that can be adjusted. These are intended for use by personnel trained in advanced cardiac life support. In addition, there are small, implanted defibrillators, which are categorized as internal defibrillators.[8]

Some AEDs turn on when the cover is opened; others are activated with a power button. All should have spare sets of sensor/defibrillator pads and batteries. The sensor/defibrillator pads have two functions: to detect cardiac waveforms and to deliver defibrillation shocks. When the pads are attached to the patient, the AED will either automatically start the analysis or prompt the user to push a button to start the analysis.

The analysis consists of comparing the patient's waveform pattern with those preprogrammed into the device. If defibrillation is needed, the AED will either automatically deliver the shock or prompt the user to push a button to deliver the shock, thus eliminating the need for the operator to be skilled at reading and interpreting EKGs.

Teaching responders not to move the patient while the AED is analyzing the waveform is important, because movement can affect the outcome. Responders should also be taught that electrical interference and running engines, such as those in emergency vehicles, can interfere with proper operation of AEDs. Ensuring a good pad-to-skin seal is important, so teaching responders to check that the gel on the electrode pads is still moist (and to ensure that the expiration date has not passed and that thick chest hair has been cut) is important.

Most AEDs have instructions printed on the device or on the defibrillator pads. Some have audible and visual prompts. The audible prompts are helpful in situations where lighting is poor; the visual prompts are helpful in noisy situations. If an error message such as "analysis halted" appears, the pads should be rechecked to be sure they are firmly attached. The amount of energy delivered will depend on whether the device is monophasic or biphasic. With a monophasic device, the energy travels in one direction only: from one pad to the other. With a biphasic device, energy travels in one direction, then stops and travels in the opposite direction. Typically, biphasic models deliver effective shocks at lower energy levels than monophasic models.[8]

New biphasic models include technology for overcoming high levels of chest impedance.[9] In some models, the amount of current automatically varies according to the amount of body resistance (impedance) in skin, fat, muscles, and lungs.[10] New features also include energy levels that automatically escalate when subsequent shocks are given -- starting at 140-250 joules and increasing to 190-360 joules.

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