In most cases bystander or layperson CPR is the best treatment a victim of cardiac arrest can receive. Clinical studies have shown that bystander CPR has a significant, positive effect on survival. This link in the chain is the arrival and act of early defibrillation with an automated external defibrillator. Most often this step is achieved with the arrival of OEMS personnel. It is however becoming more common for laypersons to be trained in this important step as well.
Early defibrillation is the step in the chain of survival that most improves survival rates.
The position of the bystander is to provide enough basic life support to keep the victim viable for the next link in the chain. Without the first two links the efforts would be far less successful if not futile. If any one link in the chain is inadequate, survival rates will be poor.