Evaluation of Intracranial Pressure Response in Rats Exposed to Complex Shock Waves

Studies on blast neurotrauma have focused on investigating the effects of exposure to free-field blast representing the simplest form of blast threat scenario without considering any reflecting surfaces. However, in reality personnel are often located within enclosures or nearby reflecting walls causing a complex blast environment, that is, involving shock reflections and/or compound waves from different directions. In fact, when a blast wave interacts with nearby structures, reflected shock waves are generated and complex three-dimensional shock waves are formed. Complex shock wave overpressure-time traces are significantly different from free-field profiles because reflections can cause super-positioning of shock waves resulting in increased pressure magnitudes and multiple pressure peaks. Very importantly, the shocks arrive from different directions which would invoke a different biomechanical response than a one-dimensional exposure. It has been reported that in complex wave environments, the extent of the injuries becomes a function of the location related to the surrounding structures rather than a function of the distance from the center of the explosion, as it is for free-field conditions (Yelverton et al. 1993; Mayorga 1997; Stuhmiller 1997). Furthermore, the resulting injuries when the individual is in confined spaces are noted to be more severe (Yelverton et al. 1993; Leibovici et al. 1996). The purpose of this study was to design a complex wave testing system and perform a preliminary investigation of the intracranial pressure (ICP) response of rats exposed to a complex blast wave environment. Furthermore, we explored the effects of head orientation in the same environment.