Cerebrospinal fluid pulse pressure and intracranial volume-pressure relationships.

In six anaesthetised and ventilated dogs the CSF pulse pressure was compared with the volume-pressure response (VPR) during continuous inflation of an extradural balloon. Both pulse pressure and VPR increased linearly with the ventricular fluid pressure (VFP) up to a mean VFP of 60 mmHg. At this pressure a breakpoint occurred above which the CSF pulse pressure showed a steeper linear increase, while the VPR remained constant. It is suggested that the breakpoint is related to failure of autoregulation, and that in non-autoregulating patients the CSF pulse pressure is a better parameter of the clinical state than the VPR.