Why are the survival numbers different?

I've had several people ask me why they keep seeing different numbers for survival percentages. Here's the heart of the problem:

1. It all depends upon what you mean by survival. In days gone by - and for very good reasons in the modern age - 'survival' meant the "return of spontaneous circulation" (Come on, folks, couldn't we just say the victim got his or her pulse back?)
2. Unfortunately, getting your pulse back doesn't always leave you at the same station. The difference is your CPC score:
   • CPC = 1 means you have no significant neurological deficit.
   • CPC = 2 means you are able to perform the activities of daily living, perhaps with some minimal accomodation.
   • CPC = 3 means you have some severe neurological deficit that interferes to varying degrees with your ability to perform the activities of daily living.
   • CPC = 4 means you are in a coma.
3. If you are measuring survival in terms of getting a pulse back, you include all CPC levels.
   
   • If you are measureing survival in terms of surviving - i.e., being able to perform the activities of daily living, you include on victims who are at CPR levels 1 & 2.
   
   • If you measure 'getting your pulse back' you will find that 9/6% of cardiac arrest victims in the CARES database do so. If you measure 'being able to perform the activities of daily living' you will get a survival number closer to 6.5%.