How to Differentiate between Monophasic and Biphasic AED Defibrillators

How to Differentiate between Monophasic and Biphasic AED Defibrillators

Automated External Defibrillators have saved millions of lives over the years. As science and technology develop and evolve, so do these devices. That is why we can differentiate AEDs into monophasic and biphasic defibrillators. The main purpose of this article is to compare these devices and describe how they differ from each other. Is the monophasic device better than the biphasic AED? Read on for more information.

Monophasic AED
Single-phase AEDs are devices that emit one type of discharge. It sends an electrical current in only one direction from an electrode on one side of the chest to an electrode on the other side. Monophasic waveform defibrillation has been used since the invention of AED devices. And thanks to advances in technology and science, it is being replaced by more effective defibrillators.

In monophasic defibrillation, the height of the capacitor voltage during charging determines the energy that the pads deliver. The waveform associated with monophasic defibrillation has a spike, which is crucial in determining defibrillation success. There must be enough current to reach the heart in order to terminate the lethal rhythm or fibrillation. At the same time, it is necessary to avoid excessively high current peaks, which could damage the patient's heart. In single-phase machines, the current supplied is high, so these machines used to be bulkier.

However, most manufacturers have ceased production of monophasic AED devices and have started producing biphasic AEDs. In turn, most hospitals use a mix of newer defibrillators and older devices.

biphasic AED
Biphasic waveform defibrillators are devices that use bidirectional current flow instead of a monophasic AED, where the current flows in one direction. These defibrillators were introduced in 1996, and with the shocks delivered by these devices, the direction of current flow reverses at some point in the defibrillation cycle during device discharge.

In biphasic AEDs, the pulse is made up of a positive and a negative spike. During the positive spike, current moves from electrode A to electrode B and vice versa during the negative spike, that is, from B to A. Modern AEDs first measure the impedance of the chest (the body's resistance to current) and adjust the voltage level. respectively. Also, devices like Mindray's BeneHeart C Series come with adult and child modes. This allows rescuers to immediately select the correct mode, which then allows the device to do its job with even greater efficiency.
The exact shape of the current delivery is determined by factors such as the current, the energy of the direction, and the duration of the energy delivered. What makes biphasic devices so important is that they match the patient's impedance through various waveform characteristics to ensure that high and low impedance patients have an equal chance of survival. This is particularly important considering that the most effective waveforms maintain their shape and duration regardless of impedance, and that is exactly what biphasic devices can achieve.

In addition to the main difference in current flow, biphasic AEDs also differ from single phase AEDs in that they achieve the same effect but with fewer joules. In fact, there is evidence to show that the efficacy of a protocol using monophasic waveform shocks in the 200-360J sequence is 90% similar to that of a protocol using biphasic waveform shocks in the 200-360J sequence. 120-200J. So what we can see here is that higher efficacy can be achieved with biphasic AEDs compared to monophasic AEDs when they have the same average delivered energy level. In order to achieve better resuscitation results for patients who are normally difficult to defibrillate, such as those with obesity or high impedance, Mindray developed 360J biphasic technology and integrated it into AED devices to increase refibrillation completion rates.
In addition, biphasic waveform defibrillation produced less deterioration in cardiac function as measured by blood pressure, heart rate recurrence, and echocardiography.