Understanding the Different AED Modes

Understanding the Different AED Modes

Before we go into understanding the different AED modes, we must stress the importance of defibrillation for cardiac arrest patients. Generally, it has been proven that the Automated External Defibrillator (AED) increases the survival rate of out-of-hospital cardiac arrest victims by 70%.

Moreover, you can use AED for different age groups – from the elderly and adults to children and infants. However, the AED is an electronic device with multiple settings, adjustments, and buttons, meaning it can be dangerous if not used properly. Additionally, there are different defibrillator types, meaning the devices have different modes of operation.

This article elaborates on the AED device and its various modes for administering electrical shocks to cardiac arrest victims.

Understanding the Different AED Modes: What Are They?

As with any other medical device, AEDs can come in different forms and shapes. For example, according to the FDA, there are two types of automated external defibrillators: semi-automated and fully-automated defibrillators. Some have adjustable modes, while others have a preset of settings you can’t alter or change.

Furthermore, there’s another distinction between the AEDs: public access AEDs and professional use AEDs. Nonetheless, all of these devices are primarily designed to analyze the heart rhythm of the cardiac arrest victim and provide info on whether you should administer shocks.

Additionally, these electronic devices have various modes and operating systems. For instance, an AED can use a monophasic waveform or biphasic waveform. Furthermore, they can recognize different heart rhythms: a shockable rhythm and an unshockable rhythm.

The waveforms are related to how the AED generates the electricity, transmits it, and produces the shockwave. On the other hand, the rhythms refer to the victim’s heart malfunctioning because of aberration or failure in the heart’s electrical conduction system. To that, the unshockable rhythm means that you can’t treat the patient with an AED.

These are the four basic modes of an automated external defibrillator. The first two are related to the device’s electrical currents and how it generates and transfers the shockwaves. The other two link to analyzing the patient’s heart and diagnosing whether you should administer an electrical shock. Now let’s take a deeper look into understanding the different AED modes.

Monophasic & Biphasic Waveforms: The Fundamentals

Even though the biphasic waveform AEDs are rapidly replacing the monophasic waveform AEDs, there haven’t been significant improvements in the survival rates. AHA’s study illustrates this within a 1-month time frame and a precondition for minimal neurological impairments.

But what is the difference between monophasic and biphasic waveforms? You can spot the differences in how they generate and transmit electrical shocks.

The Monophasic Automated External Defibrillator

Understanding the monophasic AED is crucial in understanding the different AED modes. Monophasic means the device uses an electrode to send an electrical current in a single direction – hence the name monophasic.

Another characteristic of the monophasic AEDs is that it determines the electrical energy it delivers through the pads based on the voltage capacity during charging. So, you must charge the monophasic waveform AED before administering a shock.

The monophasic AED has a single peak determining whether the defibrillation will be successful. The device needs enough electrical current to penetrate the heart and restore the proper heart rhythm. Similarly, you must avoid high peak currents when administering shocks to protect the heart from further damage.

These characteristics make the monophasic automated external defibrillator hard and sensitive to use. Some publicly-available AEDs still use monophasic waveforms. That’s why medical and emergency services learn these defibrillator modes and how to use them properly.

The Biphasic Automated External Defibrillator

The biphasic waveform defibrillator uses a bidirectional electrical current. During the discharge of the AED, the direction of the current – at some point – reverses in the defibrillation cycle. Biphasic automated external defibrillators are more effective and achieve the same effect with less power.

The biphasic AED is also more efficient for patients who are hard to defibrillate. For example, the biphasic AED can be much more effective for patients with obesity. On top of that, there are biphasic defibrillators that have an integrated 360 Joules technology to increase defibrillation.

Additionally, biphasic AEDs have proved to be more efficient in administering shocks because of the decreased number of cardiac impairments.

Moreover, this AED can adjust according to the patient’s needs and give shockwaves acceptable for both high- and low-impedance patients. Simply put, the biphasic AED finds the optimal impedance and gives everyone an equal chance of survival.

If you’re administering a shock with a biphasic AED, you’ll notice that the device has two peaks – when the device reaches the positive peak, the electrical current transfers from electrode A to B. Otherwise, when the device reaches its negative peak, the current reaches electrode B from A.

The biphasic AEDs are replacing monophasic defibrillators in public places and medical centers. That’s why if you take a basic AED certification course by AHA or an organization licensed by AHA, you’ll learn how to handle the biphasic waveform AED.

Shockable & Unshockable Heart Rhythm

Although AEDs are known as devices for administering electrical shocks, for a better understanding of the different AED modes, we must understand how it analyzes the heart’s rhythm. The device has an algorithm determining whether the cardiac arrest victim has a shockable or non-shockable heart rhythm.

The algorithms of the AED display the shockable or non-shockable condition in two different places: the left and right sides of the algorithm. If you’re using a fully automated AED, the device will immediately and independently administer the shocks.

However, if you’re using a semi-automated or manual AED, you’ll have to read the rhythm analysis results and administer the shock by yourself, if necessary.

Shockable Heart Rhythm and AEDs

Shockable heart rhythms suggest that there has been a failure or aberration of the patient’s electrical conduction system in the heart. Furthermore, a shockable heart rhythm means that you should administer an AED shock to the patient.

There Are two types of shockable heart rhythms:


      1. Ventricular Fibrillation

      1. Pulseless Ventricular Tachycardia

    In both cases, the device will detect the shockable rhythm and automatically deliver a shock. Nonetheless, in all emergencies, the experts suggest that we immediately begin with cardiopulmonary resuscitation (CPR).

    Non-Shockable Heart Rhythm and AEDs

    The Automated External Defibrillator (AED) also analyzes these rhythms. Once it notices an unshockable rhythm, the device won’t correct these arrhythmias.

    There are two types of unshockable rhythms:


        1. Asystole (the ECG monitors usually display as a flat line)

        1. Pulseless Electrical Activity (also known as PEA)

      Similar to other cardiac arrest emergencies, medical experts suggest that you immediately initiate a CPR procedure for treating Asystole and PEA.

      Modes of a Manual AED

      Understanding the different AED modes means we have to learn about the manual options. The different modes and settings aren’t only limited to fully-automated or semi-automated AEDs. The manual defibrillator also has defibrillation modes. Following are the three main modes of the manual AED:


          • Synchronized cardioversion,

          • External defibrillation,

          • Internal defibrillation.

        Manual AEDs also have another mode – the Non-invasive transcutaneous pacing (NTP), effective for clinically stable patients with the risk of decompensating.

        Other AED Types & Modes

        You can also divide the automated external defibrillators based on their modes related to the device’s location. Besides the AEDs, there are the ICDs (Implantable Cardioverter Defibrillators) and the WCDs (Wearable Cardioverter Defibrillators).

        There are some differences in the operation modes of these three defibrillator types.

        The ICD is a device that is implanted into the patient’s body in the chest or the stomach area. The device will detect the arrhythmias and the signals for a potential heart attack and act accordingly – by administering electrical shocks. The ICDs are similar to pacemakers and provide a range of low-energy and high-energy shockwaves to the patient’s heart.

        On the other hand, the doctors attach the WCDs to the patient’s skin to detect the heart’s rhythm and deliver shocks. That’s why they are called wearable cardioverter defibrillators and give alerts as soon as the arrhythmia occurs.

        Final Thoughts On Understanding the Different AED Modes

        As we’ve illustrated, there are many modes of operation and types of AEDs. Each one has specific settings which can be adjustable or used as default depending on the type of the device, its electrical composition, and usage purposes.

        Understanding the different AED modes can take time, but in general, they’re quite simple. Usually, people that have used the biphasic semi-automated defibrillator have no issue when it comes to utilizing the other types of this device. Nonetheless, taking a CPR class will teach you this skill, among other emergency actions. Now you should have a full understanding of the different AED modes.