Semi-Automatic vs. Fully Automatic AEDs

In an emergency, there are multiple types of bystander responses. Watch and panic, assume someone else will get help, or call 911. Once you call 911, you are no longer a bystander, and, increasingly, emergency dispatchers are guiding callers through the steps of CPR. You are critical to aiding victims before emergency services arrive. But, you must remain calm, cool, and collected.

In the case of cardiac arrest, there are two types of AEDs that can determine the steps you take to respond to a cardiac emergency. Even if you don’t know the first thing about defibrillators, the type of defibrillator you or a company has can change the outcome of a cardiac emergency.

The first defibrillator option is a semi-automatic AED (SAED). The AED analyzes the heart, and if a shock is warranted, the AED will say so and instruct the responder to press the shock button to deliver a shock. If the button isn’t pressed, no matter how badly the patient needs therapy, no life-saving “shock” will be delivered. The second option is a fully automatic AED (FAED). This AED analyzes the heart, and if a shock is warranted, the AED will say so, instruct bystanders to stand back with no physical contact with the victim, and delivers a shock on its own.

There are pros and cons to each option, and buyers must evaluate what’s best for them after weighing the advantages and disadvantages of each model.

Type of AED	Advantages	Disadvantages
Semi-Automatic	May help ensure all bystanders are “clear” of the victim so bystanders don’t get shocked. More control over when the victim is shocked.	More user errors2 Trained responders are taught to stay clear of the victim, so this may be an unnecessary step. All responders, including those without training, are told to step away from the patient before the AED analyzes, so this may be an unnecessary step. If responders don’t know anything about an AED, pressing the shock button can cause delays or, worse, not be pressed at all. Responders may not be able to follow through and press the button if they are about to shock a loved one or if they are in a state of shock themselves.
Fully Automatic	Ensures responders and bystanders are not touching the victim through extensive voice (and visual, in some cases) prompts. Mitigates user error1 Gives a countdown before delivering a shock. Those who are unfamiliar with AEDs don’t have to worry about actually shocking the victim (in a high-pressure situation, this might be hard to do). Eliminates the possibility that the responder will hesitate or freeze. Designed to reduce the delay in administering defibrillation therapy by responders uncomfortable with pressing a shock button.	Responders must make sure nobody is touching the victim when preparing to shock.

Both versions of the AED are equally effective at saving lives. Both allow time for bystanders and responders to take a step back and break contact with a victim. It is most important to consider the type of people who will be responding to a cardiac emergency. Will the responder maintain composure and press the shock button, or will the responder panic with the pressure of someone else’s life in their hands, not know how to use the AED, and hesitate to press the shock button?

Research concluded that though errors with AED use are rare, in the ones that do occur, 72% of the errors are because of the operator or circumstances of use. “Fully automatic AEDs may prevent the majority of these errors,” the study explained. Results showed that of 1091 shock advices, due to operator error, 33 operators failed to deliver a shock, 17 operators, instead of pressing the shock button, removed the AED in its entirety, and 8 operators pressed the “off” button.

Further research explained that “despite a lack of BLS skills and AED training, the majority of students demonstrated safe and effective use of the AED. The use of the FAED version of the CR Plus resulted in increased compliance with the protocol and reduced variability in time to deliver three shocks.” Results showed that untrained nurses showed a 0% error rate when using FAEDs and a 7% error rate when using SAEDs.

Delays between electrode attachment and first shock delivery:

Measurement	Fully Automatic (N=68)	Semi-Automatic (N=82)
Mean(S)	22	24
Range (S)	18-29	11-99

As the data indicate, SAEDs are less effective when compared to FAEDs due to delays in providing therapy. And, in cases of sudden cardiac arrest, time is of the essence. Though each is fully able to deliver the necessary shocks, the confusion it makes by having an extra button to press makes so that the shock isn’t delivered due to user error. AEDs are designed to have loud, explicit, audio instructions, and some may offer large text font and visual instructions. Designed with usability in mind, AEDs are meant to be used by anybody, even people with very little training.

Like emergency responders are trained to do, everyone likes to think that in a life-or-death emergency, he or she will remain calm. For some, this may be true, but for others, witnessing traumatic injuries can cause some hysteria. It is situations like these that responders are nervous and panicked. Time is critical when defibrillation is needed, and any hesitation to deliver a shock costs time and can cost a life. By making sure you have a FAED, you can ensure that your AED will be ready for rescue when you need it the most—no matter the skill level of the rescuer.

Footnotes:

1. https://www.sciencedirect.com/science/article/pii/S0300957217302174
2. https://www.ncbi.nlm.nih.gov/pubmed/15629554

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