The first phase , or emergency phase, keeps blood flowing through the body until the electrical system of the heart is restarted. These actions keep blood and oxygen circulating through the body until emergency help arrives.
External defibrillation is an electric shock given to the heart through paddles placed on the chest.
If a shock is needed, the device provides voice commands and screen messages that guide the person holding the paddles through the defibrillation process. An automated external defibrillator is different from a manual external defibrillator. With a manual external defibrillator, the person holding the paddles determines when a shock is needed. With an automated external defibrillator, the device analyzes the heart rhythm and determines when a shock is required. Manual external defibrillators are only used by hospital personnel or people trained to read heart rhythms such as emergency personnel in an ambulance or fire truck.