Cardiac arrest（心脏骤停） happens when the heart suddenly and unexpectedly stops pumping blood.90% of the people who have a cardiac arrest outside of a hospital die—often within minutes.That is because they do not receive treatment quickly enough to survive.Cardiac arrest is a common cause of death.It causes about 300，000 to 450
If cardiac arrest happens，rapid treatment with a medical device called automated external defibrillator （AED） can be lifesaving.Many AEDs can be easily seen in public places，schools，shopping malls，and airports.An AED system includes an AED and its necessary accessories（配件），such as a battery and pad electrodes（片状电极）verbal instructions to users，which means it gives voice instructions to tell users how to use it.
This is how an AED works.First，the user turns on the AED and follows the recorded voice instructions.Second，the user puts two electrodes on the chest of the person in cardiac arrest.Third（心律） to the AED，and then it decides whether an electric shock（电击），if a shock is needed，the AED tells the user when to press a button to give a shock.In some AEDs
