A machine which analyses the underlying rhythm in a patient who has suffered a cardiac arrest. There are four possible rhythms: asystole, pulseless electrical activity, ventricular fibrillation, and pulseless ventricular tachycardia. If the rhythm can be treated with a direct current (DC) shock (ventricular fibrillation or pulseless ventricular tachycardia) the machine will generate the appropriate DC shock, which is delivered to the patient via special pads applied to the chest. There are two types of machine: monophasic, where the shock travels mono-directionally between the pads, and biphasic where the shock travels in both directions.
Automated external defibrillator