Draw a graph and describe the effect PaCO2 has on cerebral blood flow?

  • Increases linearly between a PaCO2 range of 3-10 kPa:
    • Due to CO2 mediated vasodilatation
  • Below 3.5 kPa, cerebral vasoconstriction leads to tissue hypoxia with subsequent reflex vasodilatation and maintenance of blood flow
  • Above 10 kPa vasodilatation is maximal with no further increase in flow. Increased blood volume may lead to a rise in ICP
  • In chronic hypercapnia the curve is shifted to the right, with a higher kPa over which linear vasodilatation occurs
Relationship between PaCO2 (carbon dioxide) and cerebral blood flow