Intracranial Pressure—Theory of the Driving Pressure and a New Pressure Index

Abstract

In order to understand the pathogenesis of increased intracranial pressure, the concept of the driving pressure (DP) from the intracranial vascular system was proposed. The DP consists of combined pressure continuously transmitted from the arterial pressure (ADP) and venous pressure (VP) systems. The theoretical equation of the intracranial pressure (ICP) is expressed as follows:
ICP = ADP + VP (1)
ADP is expressed as (2).
ADP = η (BP-VP) (2)
η is defined as ΔICP/ΔBP. The authors chose the term driving pressure rate to designate this ratio. Thus, η may be taken for a kind of transfer function which can be expressed as the pressure transmission rate from the arterial system to the cerebrospinal fluid system. Measurement of the η index is simple and allows frequent checks of the often momentary changes in a patient's condition, thus providing an important index of intracranial pressure environment. Analysis of intracranial pressure by means of the driving pressure concept facilitates understanding of both mean pressure and pulse pressure. The validity of analysis of intracranial pressure in terms of the driving pressure was shown from clinical data and animal experiments.