Date
16 October 2018
An automated external defibrillator (AED) at a Frankfurt Airport railway station. An AED is used to deliver electric current and stop chaotic patterns of heart activities like a switch is turned off. Photo: Internet
An automated external defibrillator (AED) at a Frankfurt Airport railway station. An AED is used to deliver electric current and stop chaotic patterns of heart activities like a switch is turned off. Photo: Internet

How an automated external defibrillator works

The heart is such a wonderful organ that keeps the entire body alive. It has four chambers: two atria receiving blood and two ventricles pumping it to the lungs and the rest of the body.

The atria and ventricles are formed by cardiac muscles. The muscles contract at about the same time in order to maximize the power of each pump. They are like the switch and wiring network of a lighting system.

Cardiac muscle fibers are a network of fibers. Signals are sent across the network of fibers at a specific speed and time sequence to enable coordinated contraction.

Electrocardiography (ECG) is used to monitor the health of this fiber network. If the network is not stable, the cardiac muscle cells will contract at their own pace and the heart will vibrate as if it is trembling.

When blood is not pumped out effectively, blood circulation will stop and the brain will die within several minutes due to lack of oxygen.

If an automated external defibrillator (AED) is used during such a crucial moment, the heart has a 75 percent chance of resuming work again.

An AED delivers electric current and stops chaotic patterns in the heart like a switch is turned off.

The use of electric current to enable coordinated contraction of the heart is a relatively new discovery. In 1947, a surgeon called Claude Beck noticed during surgeries that there could be a sudden ventricular fibrillation, or cardiac rhythm disturbance, in patients whose hearts were perfectly healthy. Some hearts would return to normal but others wouldn’t.

Combining his own clinical experience, he performed the first known defibrillation on a teenager who went into cardiac arrest. The patient was able to make a full recovery eventually.

Most patients below the age of 40 who experience cardiac arrest have dysfunctional cardiac muscle fibers. The timely use of an AED can save their lives.

AEDs are no longer restricted to hospitals. Nowadays, even large shopping malls and sports centers are equipped with the device.

In some countries, secondary students are taught how to administer first aid and use an AED as part of the school curriculum.

This article appeared in the Hong Kong Economic Journal on May 4

Translation by John Chui

[Chinese version 中文版]

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