cpp equation

Has anyone heard of the following equation to get a cpp value without a bolt or ventric in place. Equation goes as follows: map-cvp=cpp. This equation was recently brought to my attention, and my co-workers and I have discussed it quite thoroughly and have yet to find any literature about it. Let me know........

Cerebral perfusion pressure (CPP) and autoregulation

• CPP is proportional to mean arterial pressure (MAP)
  
• if ICP > right atrial pressure (RAP), then
  CPP = MAP - ICP
  
• if RAP > ICP, then
  CPP = MAP - RAP (CVP is a measure of RAP)

http://www.metrohealthanesthesia.com/edu/neuro/icTumors1.htm

Also google "cerebral perfusion pressure and right atrial pressure" and you will have your answers.

66F