Blast-Induced Biomechanical Loading of the Rat: An Experimental and Anatomically Accurate Computational Blast Injury Model

Abstract

Blast waves generated by improvised explosive devices (IEDs) cause traumatic brain injury (TBI) in soldiers and civilians. In vivo animal models that use shock tubes are extensively used in laboratories to simulate field conditions, to identify mechanisms of injury, and to develop injury thresholds. In this article, we place rats in different locations along the length of the shock tube (i.e., inside, outside, and near the exit), to examine the role of animal placement location (APL) in the biomechanical load experienced by the animal. We found that the biomechanical load on the brain and internal organs in the thoracic cavity (lungs and heart) varied significantly depending on the APL. When the specimen is positioned outside, organs in the thoracic cavity experience a higher pressure for a longer duration, in contrast to APL inside the shock tube. This in turn will possibly alter the injury type, severity, and lethality. We found that the optimal APL is where the Friedlander waveform is first formed inside the shock tube. Once the optimal APL was determined, the effect of the incident blast intensity on the surface and intracranial pressure was measured and analyzed. Noticeably, surface and intracranial pressure increases linearly with the incident peak overpressures, though surface pressures are significantly higher than the other two. Further, we developed and validated an anatomically accurate finite element model of the rat head. With this model, we determined that the main pathway of pressure transmission to the brain was through the skull and not through the snout; however, the snout plays a secondary role in diffracting the incoming blast wave towards the skull.

Fluid percussion injury device for the precise control of injury parameters

“…peak pressure in the fluid percussion model) to severity in terms of brain pathology and behavioral outcomes. The contributions that the temporal characteristics of the injury such as rise time and duration have on damage to the brain have just begun to be investigated (Cater et al, 2005;Magou et al, 2011;Ganpule et al, 2013;Sundaramurthy et al, 2012).…”

“…It is used to deform the brain of rodents to produce both focal and diffuse injury characteristics (Cortez et al, 1989;Dixon et al, 1987;Graham et al, 2000;Hicks et al, 1996;Morales et al, 2005;Thompson et al, 2005). Potentially, one of the biggest contributors to differences in TBI outcome could be the rate at which pressure changes in addition to magnitude of pressure that deforms the brain (Magou et al, 2011;Ganpule et al, 2013;Sundaramurthy et al, 2012). The term "rate" is defined as the rise time to peak pressure.…”

“…The contribution of the rate of injury was recognized in early head injury physical models (Sundaramurthy et al, 2012;Shuck and Advani, 1972;Arbogast et al, 1997;Smith et al, 1997;Liu et al, 1975;Adams et al, 1983;King et al, 2003), where injury was correlated with rotational acceleration of the head. Currently, there are no animal models directly examining whether the pathophysiological outcome of injury depends on the rate of the delivered injury.…”

On the prospective contributions of the shock physics community to outstanding issues concerning blast-induced traumatic brain injury

“…However, it is unfortunately not standard practice. While few researchers have purposely designed experiments to generate scaled-down exposure conditions [14,32,33] against small mammals, others expose animal models to blast parameters relevant to humans [27,[34][35][36][37][38][39][40][41][42][43]. Assuming mass scaling is relevant to bTBI, some of these exposures may effectively result in exposing an animal model to nuclear-sized blasts [29].…”

“…Recently, the awareness of conventional shock tube limitations has grown [37,46]. In addition, an increase in the use of advanced blast simulators (ABS), a shock tube with expanding cross section assembled with an end-wave eliminator, has been observed [43,[47][48][49][50].…”