If no one responds to the call for help, the rescuer first activates the emergency response system and then begins basic life support by giving 30 chest compressions at a rate of 100 to 120 / minute and a depth of 5 to 6 cm, allowing the chest wall to return to full height between compressions, and then opening the airway (lifting the chin and tilting back the forehead) and giving 2 rescue breaths.