Draw a graph and describe the effect PaO2 has on cerebral blood flow?

  • At ‘normal’ PaO2 of >8 kPa there is minimal effect on cerebral blood flow
  • As PaO2 falls below this level there is a rapid rise in cerebral blood flow:
    • Mediated by hypoxia-induced vasodilation
    • Results in a CBF of around 110ml/100g/min at a PaO2 of 4.0 kPa
    • May contribute to further rises in ICP in patients with head injury
Relationship between PaO2 (oxygen) and cerebral blood flow