Adults who suddenly collapse and are not responsive are likely to have sudden cardiac arrest and their chance of survival is nearly zero unless someone takes action immediately. You should call 911 and start giving hard and fast chest compressions in the center of the chest. If sudden cardiac arrest is the cause of the collapse, Hands-Only™ CPR is an easy, effective way for any bystander to more than double the victim's chance of survival. If an adult has collapsed for reasons other than sudden cardiac arrest, Hands-Only™ CPR should still help by causing the person to respond (begin to move, breathe normally or speak). If that occurs, Hands-Only™ CPR can be stopped.