Date of this Version
UCARE Poster session, University of Nebraska-Lincoln Research Fair, April 2016, Lincoln, NE.
Cerebrovascular reactivity (CVR) is an important regulatory factor of the brain. The parameter controls the dilation and constriction of blood vessels in the brain in response to certain stimuli, such as carbon dioxide. Abnormal CVR values could potentially be indicators of poorly functioning regulatory systems. Testing of CVR is one method of assessing the brain's regulatory capabilities. The purpose of this study was to test for a relationship between CVR and intracranial pressure (ICP).
In this study, increased intracranial pressure was created in 4 female subjects through head down tilt, using an inversion table. Subjects were lowered in the table and secured in 15 degree increments, from positive 45 degrees, to negative 30 degrees. At each level, a breath holding test was performed to measure CVR. In the breath holding test, the subject breathed normally for 30 seconds, held their breath for 30 seconds, and breathed normally for 30 seconds while blood flow velocity was recorded in the middle cerebral artery. The subject’s blood pressure was taken at each level of the table.
The blood flow velocities from the middle cerebral artery were used to calculate the subject’s CVR value for each angle. The CVR values were observed to not change significantly at different angles of the inversion table. As mean arterial pressure was also observed to have remained unchanged through the various angles of the inversion table, it was confirmed that ICP was being increased.