Check the victim for unresponsiveness. If the person is not responsive and not breathing or not breathing normally. Call 999 and return to the victim. In most locations the emergency dispatcher can assist you with CPR instructions.
If the victim is still not breathing normally, coughing or moving, begin chest compressions. Push down in the center of the chest 2 inches 30 times. Pump hard and fast at the rate of at least 100/minute, faster than once per second.