Non-invasive method of determining absolute intracranial pressure

#This patent application is co-pending with one related patent application entitled “NON-INVASIVE METHOD OF DETERMINING DIASTOLIC INTRACRANIAL PRESSURE” (NASA Case No. LAR 16440-1), by the same inventors as this patent application.

#1. Field of the Invention

#This invention relates to determination of intracranial pressure. More specifically, the invention is a non-invasive method for determining the absolute intracranial pressure in a patient.

#FIG. 1 is a schematic view of the skull and brain of a patient with the brain being coupled to the patient's heart;

#FIG. 2 is a schematic view of a system that can be used to measure/monitor skull expansion in a patient for use by a method of the present invention;

#FIG. 3 is a graph of a patient's skull expansion versus time as measured by, for example, the system in FIG. 2; and

#Referring now to the drawings, and more particularly to FIG. 1, a patient's skull 10 is illustrated with his brain referenced by numeral 12. As is well known, brain 12 is a venous structure that is coupled to the patient's heart 14 and, therefore, undergoes systolic-diastolic changes in blood pressure. The blood pressure in the venous bed of the brain is known as venous bed pressure and will be referenced herein as PVB. Surrounding brain 12 is the patient's cerebrospinal fluid (CSF) 16, the pressure of which is known as intracranial pressure or ICP as it will be referenced herein.

#Skull 10 tends to expand and contract with changes in ICP. However, the compliance (i.e., the ability of skull 10 to expand with increasing ICP) of skull 10 is not sufficient to accommodate the pressure regulation needed for proper circulation of blood within brain 12 and the patient's CSF system (not shown). Accordingly, pressure within skull 10 is controlled by compliance of the brain's venous bed in association with the addition/removal of CSF 16. The determination and/or continuous monitoring of the absolute ICP of CSF 16 is important in determining whether or not a patient has a problem interfering with the body's natural ability to control ICP.

#In terms of skull expansion, the present invention takes note of the fact that the venous bed pressure PVB will be equal to ICP when skull 10 is neither expanding nor contracting for a skull expansion of “zero.” As is known in the art, venous bed pressure PVB can be determined from a standard arterial blood pressure measurement thereby making ICP easily determined at a time of zero skull expansion. Once ICP at zero skull expansion (or ICPREF as it will be referred to hereinafter) is determined, the present invention goes on to determine absolute ICP by measuring skull expansion changes brought about by associated known changes in ICP.