Asimple mathematical model of the interaction between intracranial
pressure and cerebral hemodynamics.
Ursino, Mauro, and Carlo Alberto Lodi.
Department of Electronics, Computer Science and Systems, University
of Bologna, viale Risorgimento 2, I 40136 Bologna, Italy
APStracts 3:0527A, 1996.
The paper presents a simple mathematical model of intracranial
pressure (ICP) dynamics, oriented to clinical practice. It includes
the hemodynamics of the arterial-arteriolar cerebrovascular bed,
cerebrospinal fluid (CSF) production and reabsorption processes, the
non-linear pressure-volume relationship of the craniospinal
compartment, and a Starling resistor mechanism for the cerebral
veins. Moreover, arterioles are controlled by cerebral autoregulation
mechanisms: the latter are simulated by means of a time constant and
a sigmoidal static characteristic. The model is used to simulate the
interactions between ICP, cerebral blood volume and autoregulation.
Three different related phenomena are analyzed, i.e., the generation
of plateau waves, the effect of acute arterial hypotension on ICP,
and the role of cerebral hemodynamics during Pressure Volume Index
(PVI) tests. Simulation results suggest that: i) ICP dynamics may
become unstable in subjects with elevated CSF outflow resistance and
decreased intracranial compliance, provided cerebral autoregulation
is efficient. Instability manifests itself with the occurrence of
self-sustained plateau waves. ii) Moderate acute arterial hypotension
may have completely different effects on ICP, depending on the value
of model parameters. If the physiological compensatory mechanisms
(CSF circulation and intracranial storage capacity) are efficient,
acute hypotension has only negligible effects on ICP and cerebral
blood flow (CBF). By contrast, if these compensatory mechanisms are
poor, even modest hypotension may induce a large transient increase
in ICP and a significant transient reduction in CBF, with risks of
secondary brain damage. iii) The ICP response to a bolus injection
(PVI test) is sharply affected, via cerebral blood volume changes, by
cerebral hemodynamics and autoregulation. We suggest that PVI tests
may be used to extract information not only on intracranial
compliance and CSF circulation, but also on the status of mechanisms
controlling CBF.
Received 21 June 1996; accepted in final form 29 October 1996.
APS Manuscript Number A578-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996