A whole-body mathematical model for intracranial pressure dynamics.
Most attempts to study intracranial pressure using lumped-parameter models have adopted the classical "Kellie-Monro Doctrine," which considers the intracranial space to be a closed system that is confined within the nearly-rigid skull, conserves mass, and has equal inflow and outflow. The present work revokes this Doctrine and develops a mathematical model for the dynamics of intracranial pressures, volumes, and flows that embeds the intracranial system in extensive whole-body physiology. The new model consistently introduces compartments representing the tissues and vasculature of the extradural portions of the body, including both the thoracic region and the lower extremities. In addition to vascular connections, a spinal-subarachnoid cerebrospinal fluid (CSF) compartment bridges intracranial and extracranial physiology allowing explict buffering of intracranial pressure fluctuations by the spinal theca. The model contains cerebrovascular autoregulation, regulation of systemic vascular pressures by the sympathetic nervous system, regulation of CSF production in the choroid plexus, a lymphatic system, colloid osmotic pressure effects, and realistic descriptions of cardiac output. To validate the model in situations involving normal physiology, the model's response to a realistic pulsatile cardiac output is examined. A well-known experimentally-derived intracranial pressure-volume relationship is recovered by using the model to simulate CSF infusion tests, and the effect on cerebral blood flow of a change in body position is also examined. Cardiac arrest and hemorrhagic shock are simulated to demonstrate the predictive capabilities of the model in pathological conditions.
Lakin
William D
WD
Department of Mathematics and Statistics, University of Vermont, 16 Colchester Avenue, Burlington 05401-1455, USA. wlakin@together.net
Stevens
Scott A
SA
Tranmer
Bruce I
BI
Penar
Paul L
PL
D001794:Blood Pressure / Q000502:physiology; D001921:Brain / Q000098:blood supply* / Q000502:physiology*; D002302:Cardiac Output; D002555:Cerebrospinal Fluid / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology; D003198:Computer Simulation; D005110:Extracellular Space / Q000502:physiology; D006323:Heart Arrest / Q000503:physiopathology; D006487:Hemostasis; D006801:Humans; D006874:Hydrostatic Pressure; D007427:Intracranial Pressure / Q000502:physiology*; D008955:Models, Cardiovascular; D011187:Posture / Q000502:physiology; D011673:Pulsatile Flow / Q000502:physiology; D012771:Shock, Hemorrhagic / Q000503:physiopathology; D013564:Sympathetic Nervous System / Q000502:physiology