3.4
The Heart How a Defibrillator Works
Defibrillators are medical devices that deliver a life saving shock of electricity.
Electrode pads that are connected to the defibrillator are placed on a patient’s bare chest and the software within the defibrillator analyses the electrical activity of the heart.
If the electrical activity present in the heart is a rhythm that requires a shock (VF or VT) then the defibrillator will instruct “shock advised” and it will charge itself in preparation for delivering a shock.
If it is a semi-automatic defibrillator that the rescuer is using they will be advised to push a button to deliver the life saving shock of electricity. If it is a fully automatic defibrillator, the defibrillator will begin to count down before automatically delivering the shock.
If the defibrillator analyses the heart and there is no electrical activity of the heart (known as Asystole) or they have a normal heartbeat Normal Sinus Rhythm (NSR) then the defibrillator will instruct “no shock is advised”.
Once a shock passes through the heart, it stops the heart briefly, (a big misconception is that it restarts the heart), and the heart’s own pacemaker retakes control then heart begins to beat normally again and pumps oxygenated blood around the body.
“An AED actually stops the heart rather than restarting it. It is the heart’s own pacemaker that then retakes control and the heart begins to beat normally again”
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