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We have spoken about CPR and what we are doing until the AED arrives. What we are going to do now is just briefly look at what an AED unit is and why we want to use one. An AED is an automatic external defibrillator. Now, one of the myths of an AED unit is that it actually starts the heart, but what is actually happening is it interrupts the abnormal twitching of the heart that hopefully then, the pacemakers will fire and restart the heart in a normal beating pattern. When someone needs CPR, the heart does not always just stop. Electric activity in the heart can cause it to quiver. This is not producing any meaningful pulse. By delivering a shock across the heart, we interrupt this electric activity and hope that naturally will start beating normally again. AED units will only advise of a shock if they detect what's called a shockable rhythm. A shockable rhythm would be when the heart goes into VF, ventricular fibrillation or pulseless VT, ventricular tachycardia.

Now, from a first aid point of view, we do not need to worry about the difference because the unit will detect it and decide if it is shockable or not shockable. If it's not shockable, this would mean that the heart is beating normally, called a normal sinus rhythm or its flatline called asystole. There are many different types of AED units, but they all work in the same way and they all talk you through using them. Some, you have to push a shock button when advised, these are called semi-automatic AEDs, and the others may automatically shock. These are called automatic AEDs. In the coming videos, we are to look at AEDs in more depth and how to use them.