S.A. Stevens and W.D. Lakin
 

Abstract

The experimentally-measured pressure-volume relationship for the human intracranial system is a nonlinear "S-shaped" curve with two pressure plateaus, a point of inflection, and a vertical asymptote at high pressures where all capacity for volume compensation is lost.  In lumped-parameter mathematical models of the intracranial system, local compliance parameters relate volume adjustments to dynamic changes in pressure differences between adjacent model subunits.  This work explores the relationship between the forms used for local model compliances and the calculated global pressure-volume relationship.  It is shown that the experimentally-measured global relationship can be recovered using physiologically motivated expressions for the local compliances at the interfaces between the venous-cerebrospinal fluid (CSF) subunits and arterial-CSF subunits in the model. Establishment of a consistent link between local model compliances and the physiological bulk pressure-volume relationship is essential if lumped-parameter models are to be capable of realistically predicting intracranial pressure dynamics.