What does
"Defibrillator" mean?

What does it do?

De = to undo, or reverse
Fibrillate = uncoordinated contractions of the heart

It stops fibrillation of the heart, and restores the normal coordinated contractions.

The cells inside the heart muscle conduct electrical current. Some cells in the heart (pacemaker cells) charge by themselves regularly, and they cause the other cells to charge. A current flows the heart muscle in a particular way. Every time this happens the heart muscle contracts and pumps the blood - 'heart beat". This coordinated electrical pattern is essential to cause the heart to fill and empty with every beat pushing blood around the body.
When this electrical pattern becomes uncoordinated (fibrillation), the heart muscle contractions are not coordinated and no blood is pumped. This will lead to decreased blood pressure, lack of oxygen, heart muscle damage, and untimley death. The defibrillator is used to reverse this fibrillation and restore the coordinated contractions. It can also be used if the heart has stopped beating to start it again. (e.g. after an electric shock)

The defibrillator uses the mains power or a large internal battery to charge a large capacitor to between 5 and 400 Joules. Two metal "paddles" (electrodes) are connected from the defibrillator, and placed on either side of the patient's chest. The energy stored in the capacitor is then discharged from one paddle to the other through the patient's chest, which shocks the heart into beating rythmically again Defibrillators also have built in ECG monitors, and ECG recorders to continuously display and document ECG waveforms.