The Automated External Defibrillator (AED) is a life-saving device designed for people to defibrillate patients who collapse unexpectedly after experiencing sudden cardiac arrest (SCA) by delivering a high-energy electric shock to restore normal and regular heart rhythm. The earliest innovation in AED defibrillators delivered the current in one direction between two electrodes called a monophasic damped sine wave, which is conducted by a monophasic AED. However, with the continuous innovation and development of technology, the biphasic AED has become the mainstream and preferred intervention for SCA patients.
Even though there has been much debate regarding biphasic vs. monophasic defibrillators in recent years. As for the concern of biphasic vs. monophasic defibrillator, which one should go for, we are going to discuss this in the following sections.
Monophasic Defibrillator
Monophasic defibrillation features one direction of the current and delivers the electrical current from one electrode on one side to another electrode on the opposite side. Therefore, the peak current in monophasic AED is the key determinant of successful defibrillation when there is no impedance detection. The voltage and joules of a monophasic defibrillator are higher than a biphasic one, and it can only be used on patients with no breath.
In this case, monophasic defibrillators are suggested to provide a peak current of 360 Joules to cover a wide range of SCA patients with high body impedance. This makes monophasic AED heavy and difficult to carry. The high-energy shock is easy to leave burns on a patient’s chest and causes myocardial dysfunction after AED shocks.
Biphasic Defibrillator
As time went by, the medical field evolved more, and biphasic defibrillators came into being. A new waveform technology was invented, known as biphasic waveform defibrillation. As the name indicates, a biphasic AED defibrillator sends current in two directions. The first phase is similar to the monophasic AED defibrillator because the current goes from one pad to another. But in the second phase, the flow of current becomes the opposite. The advantage of a biphasic defibrillator is that it can give a guided wave after the one-wave ends the cardiac disturbance clutter. This guided wave is close to the heart’s electrical signal, which is more effective in getting the heart pumping again.
Compared with the monophasic waveform, biphasic waveform defibrillation can detect the patient’s body impedance and automatically adjust their consistency and shape so that SCA patients with different body impedances receive a preset amount of shock energy. This is done to guarantee that SCA patients having high impedance will be likely to survive as those who have low impedance. Besides that, biphasic defibrillators cause little damage to patients’ myocardial function as they provide a lower current. Different AED brands of biphasic defibrillators use different waveform techniques, but mainly a Biphasic Truncated Exponential (BTE) waveform and a Biphasic Rectilinear Waveform (BR) waveform, both of which show similar efficacy in the elective cardioversion of atrial fibrillation.[1]
Biphasic vs. Monophasic Defibrillators
Traditional monophasic AEDs have an energy level in joules (J) ranging from 200J to 300J to a maximum of 360J, which can potentially cause damage to the patient’s myocardial function, as mentioned above. Typically, the default starting energy of a biphasic defibrillator is 200 joules, but the energy of the current can be adjusted depending on the patient’s condition. For example, when a biphasic AED is used to defibrillate an infant, the energy is reduced to a very low level.
It is reported that biphasic AED delivers equal or improved efficacy at lower energies as opposed to the 200-joule monophasic AED.[2] Low-energy biphasic waveform defibrillation has been tested in experimental and clinical settings in VF as an alternative to monophasic waveform defibrillation with conventional incremental energy.[3] A biphasic electric current waveform has higher efficiency, needs lower energy, and very fewer shocks as compared to the monophasic waveform. With the biphasic defibrillator, the probability of aftershock complications (skin burn or myocardial dysfunction) is very low, so a biphasic AED defibrillator is safer for SCA patients. Moreover, the biphasic defibrillator is as lightweight as a lunch box, which is why so many public places have access to this device.
Wrapping Up
The technological advancement in defibrillation has saved the lives of millions. While the monophasic AED defibrillator served as a standard go-to life-saving device, the invention of the biphasic AED defibrillator has significantly boosted the exposure and availability of this innovation.
A shining example is Mindray AED which boasts intuitive interaction, fast problem-solving skills, quick shock delivery, and an innovative management platform. Mindray is one of the leading professional AED companies around the world, providing high-quality biphasic AEDs. Based on biphasic technology, the delivered energy of Mindray’s biphasic AED can be escalated to a maximum of 360J, allowing you to improve the defibrillation success ratio by increasing the dose of subsequent AED shocks. Its AED also comes with an interactive voice and visual image guidance, which offers a great user experience and hassle-free operation. Furthermore, the workflow is made simpler with fast programming of key parameters and an innovative user interface. If you are considering a biphasic AED solution, Mindray could be your choice.
References:
[1] A comparison of rectilinear and truncated exponential biphasic waveforms in elective cardioversion of atrial fibrillation: A prospective randomized controlled trial. Resuscitation 2013, Volume 84, Issue 3, Page 286-291. Available at:
https://www.resuscitationjournal.com/article/S0300-9572(12)00367-X/fulltext (Accessed: 9 October 2022)
[2] Demystifying biphasic defibrillation. Nursing 2005, Volume 35, Issue 8, August 2005, Pages 6-11. Available at: https://journals.lww.com/nursing/Fulltext/2005/08001/Demystifying_biphasic_defibrillation.2.aspx (Accessed: 21 February 2022)
[3] Wanchun Tang, Max Harry Weil. Chapter 1 – Cardiac Arrest and Cardiopulmonary Resuscitation. Critical Care Medicine (Third Edition), 2005, Pages 3-15. Available at: https://www.sciencedirect.com/science/article/pii/B9780323048415500030 (Accessed: 21 February 2022)
