Results from isolated blood vessel studies show a graded physiologic response to a mechanical stretch stimulus. The measured response for venous components shows a developed isometric force post injury that can be broadly grouped into four categories ranging from 2 to 14 grams. This corresponds to an average decrease in diameter as the specimen length is held constant of approximately 12%. In addition, the arterial components showed a developed force of 2 to 4 grams occurring only at very high strain values. These developed forces were compared to chemical control values for contraction of the whole vessel using a saturated KCl solution.

To conduct these experiments an appropriately scaled materials testing device has been developed. This device consists of a solenoid driver, an isometric force transducer, a linear variable displacement transducer, as well as a fluid reservoir system for tissue maintenance and controlled perfusion.

Results from primate studies show a transient increase in ICP to a non-impact inertial loading condition. The measured ICP increase correlates linearly to the peak tangential load in these experiments. An ICP ratio (maximum/baseline) is defined which ranges from 2 to 7. These ratios were compared to metabolite assays of whole primate brain slices. The metabolite studies showed maximum decreases in ATP of 80 percent of normal. These values were then correlated to principal strains in the same regions of the brain using physical model experiments. These studies point to possible alterations in cerebral blood flow due to mechanical loading.

A series of experiments involving dynamic elongation of fluid and air filled elastic tubes have been conducted to simulate the effects of traumatic injuries on blood vessels. The polymer tube physical model allows us to more closely study the coupled fluid and solid mechanics problem associated with cerebral blood vessels undergoing high strain rate loading. The strains used in these studies are comparable to those associated with traumatic head injuries. Comparisons between fluid and air filled elastic tubes show stiffness associated with perfusion ranging from 10 to 43%. We have developed, in parallel, mathematical models of the tubes which allow us to investigate the effects on the mechanics of the wall. These models provide the link between macroscopic experiments on whole blood vessels and studies involving cellular mechanisms of injury.