title: Measuring Hemodynamic Changes in the Ophthalmic Artery During Applied Force for Noninvasive Intracranial Pressure Monitoring: Test Results in a Porcine Model.
abstract: Possible traumatic brain injury victims would greatly benefit from a handheld, noninvasive intracranial pressure (ICP) monitoring tool, which a medic could operate in a remote area. Such a device would also benefit the transport of injured soldiers during en route medical care and critical care air transport. This study demonstrates the use of noninvasive blood flow measurements in the eye by ultrasound as a proxy for ICP. ICP was artificially raised in a porcine model and resultant blood flow change in the ophthalmic artery was measured. In addition, the ultrasound transducer itself was used to compress the eye further altering ophthalmic hemodynamics. Blood flow velocities at a range of applied forces and ICP were compared. It was found that 3.25 N of force applied to the cornea was sufficient to produce significant changes in ophthalmic artery blood dynamics regardless of the ICP value. Specifically, the change in resistivity index (RI) and pulsatility index (PI) as force was applied to the cornea correlated with ICP levels. In multiple animal experiments, the magnitude of PI/RI percent change was inversely related to differences in ICP. Force applied to the cornea at baseline ICP resulted in a 15% increase in PI/RI. Results indicate that as ICP increases, the percent change in PI/RI while force is applied decreases. The consistency of data collected indicates that a trend line developed with this data and from similar experiments could be used as a predictive measurement of ICP.
authors.affiliation: Biomedical Imaging and Biosignal Analysis Laboratory, Department of Biological Systems Engineering, University of Nebraska-Lincoln, 230 Chase Hall, Lincoln, NE 68583-0726.
authors.forename: Max
authors.initials: M
authors.lastname: Twedt
authors.affiliation: Center for Advanced Surgical Technology, 986245 Nebraska Medical Center, Omaha, NE 68198.
authors.forename: Chase
authors.initials: C
authors.lastname: Pfeifer
authors.affiliation: Cerebrovascular Neurosurgery, University of Nebraska Medical Center, 42nd and Emile Street, Omaha, NE 68198.
authors.forename: William
authors.initials: W
authors.lastname: Thorell
authors.affiliation: Biomedical Imaging and Biosignal Analysis Laboratory, Department of Biological Systems Engineering, University of Nebraska-Lincoln, 230 Chase Hall, Lincoln, NE 68583-0726.
authors.forename: Greg
authors.initials: G
authors.lastname: Bashford
mesh_terms: D000818:Animals; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D007427:Intracranial Pressure; D008991:Monitoring, Physiologic / Q000379:methods*; D009880:Ophthalmic Artery / Q000503:physiopathology*; D013552:Swine / Q000502:physiology; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods / Q000592:standards*