yeap, we have all heard it, seen it, and probably tried it (or will try it), but how exactly does an AED work?
First of all...what is an AED?
AED stands for Automated External Defibrillator. An AED is a device used to administer an electric shock through the chest wall to the heart. Built-in computers assess the patient’s heart rhythm, judge whether defibrillation is needed and then administer the shock. Audible and/or visual prompts guide the user through the process.
Will an AED always resuscitate someone in cardiac arrest?
An AED only works in 2 situations - when the casualty is going through Ventricular Fibrillation (VF), or Ventricular Tarchycardia (VT). Most patients, when they become pulseless go through a brief period of VF. An AED only treats a fibrillating heart (heart that still has rhythm). VF eventually deteriorates into a total absence of electrical activity, often around ten to fifteen minutes after arrest. In cardiac arrest without any heart rhythm at all, the heart does not respond to an AED, and requires CPR instead.
Err...how does a heart looks like ah?
Blood comes in from the atria (plurar of atrium!), and goes out from the ventricles!
The atria and ventricles work as a team — the atria fill with blood, then dump it into the ventricles. The ventricles then squeeze, pumping blood out of the heart.
What is Ventricular Tarchycardia (VT)?
VT is a rapid heart rhythm originating within the ventricles. VT tends to disrupt the orderly contraction of the ventricular muscle, so that the ventricle's ability to eject blood is often significantly reduced. That, combined with the excessive heart rate, can reduce the amount of blood actually being pumped by the heart during VT to dangerous levels. Consequently, patients with VT often experience -- in addition to palpitations -- extreme lightheadedness, loss of consciousness, or even sudden death.
the above diagram shows the difference between a normal heart rate (top), and VT (bottom)
Or to understand that simply...the heart rhythm is messed up.
What is Ventricular Fibrillation (VF)?
VF is closely related to VT. However, VF is a much more disorganized rhythm that immediately brings to a halt all meaningful ventricular contractions. Blood immediately stops flowing, and loss of consciousness occurs within seconds. Unless cardiopulmonary resuscitation is started within a few minutes of the onset of VF, sudden death will occur.
the heart rhythm is fast (300 to 600!), and extremely irregular..that's VF for you!
Or to understand that simply...the heart rhythm is really, really, really messed up.
Why does someone having a heart attack need an AED?
When a heart attack becomes a full cardiac arrest, the heart most often goes into uncoordinated electric activity called ventricular fibrillation. The heart twitches ineffectively and can’t pump blood.
When a heart attack becomes a full cardiac arrest, the heart most often goes into uncoordinated electric activity called ventricular fibrillation. The heart twitches ineffectively and can’t pump blood.
The AED delivers electric current to the heart muscle, momentarily stunning the heart and stopping all activity. This gives the heart an opportunity to resume beating effectively. While the heart pauses, the small piece of tissue responsible for the next impulse (the sinus node or sinoatrial node) should fire off the next heart beat.
Video
If you're confused by all that rubbish above, this video should clear it up a little! :)
:D please do not try this
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