New Advanced Blast Simulator research node expands opportunities for studying brain injury

John Travis Parsons, PhD

About 15 years ago, Travis Parsons, PhD, was working in the Department of Neurology at Virginia Commonwealth University (VCU) and pursuing his careerlong interest in epilepsy research. After his first postdoctoral position came to an end, Dr. Parsons soon found his way to Bruce Spiess, MD, who at the time was a Professor of Anesthesiology at VCU.

Dr. Spiess was seeking a postdoctoral researcher to use retinal angiography to assess the ability of perfluorocarbon emulsions (PFCs) to decrease vasculature bubble load associated with decompression illness. Dr. Parsons, now an Assistant Professor of Anesthesiology at UF, and Dr. Spiess, now a Professor of Anesthesiology and Vice Chair of Research at UF, have worked together since. And the collaboration soon led Dr. Parsons back to epilepsy research.

The Office of Naval Research (ONR) in the Department of Defense (DoD), which was funding Dr. Spiess’ research and the postdoctoral position, was interested in the ability of PFCs to dissolve the inert gas nitrogen that is the source of deadly arterial bubbles linked to decompression illness. The ONR was also interested in effective treatments for traumatic brain injury (TBI).

Drs. Parsons and Spiess convinced the ONR that if PFCs could dissolve and remove nitrogen to improve outcomes related to decompression illness, PFCs could dissolve oxygen and carry it to the brain to improve outcomes concomitant with TBI. This led to a three-year ONR-funded study led by Dr. Parsons investigating the ability of PFCs to improve outcomes after TBI. The Advanced Blast Simulator (ABS) was built during this time with ONR funding, which led to Dr. Parsons’ interest in single and repetitive mild blast TBI and military operational blast exposure injury models.

Advanced Blast Simulator
Advanced Blast Simulator. From right to left: driver section (A), transition section (B), test section (C), end wave eliminator (D).

Now, with a fully operational ABS housed in our department, Dr. Parsons has come full circle by using the repetitive blast model to study posttraumatic epilepsy (PTE). In the five months since the ABS has been functional, the research node has formed a collaboration, generated preliminary data, and submitted a multicenter multiyear grant in March 2021.

Dr. Parsons is collaborating with Prodip Bose, MD, PhD, Associate Professor of Anesthesiology, Neurology, and Physiological Sciences as well as Director of the MRI and Translational Neurotrauma Rehabilitation Laboratory and Associate Director of the Brain Rehabilitation Research Center (both at the Malcom Randall VA Medical Center). Preliminary data are being gathered through a VA pilot grant to pursue larger multiyear DoD/National Institutes of Health (NIH) grants investigating molecular mechanisms and treatments of PTE.

Dr. Parsons has also been invited by the Program Director of Epilepsy at the NIH/National Institute of Neurological Disorders and Stroke to participate in a four-part workshop titled “Post-Traumatic Epilepsy: Models, Common Data Elements and Optimization” starting in March 2021.

The ABS, which is 2.5 feet in diameter and 25 feet long, can generate a simple free-field Friedlander wave that mimics what occurs when an improvised explosive device (IED) detonates in an open field.

“It is a resource that is unique to the university and to the southeast United States as well,” said Dr. Parsons. “It is considered the gold standard for laboratory blast research and I hope to make it available to others who are interested in TBI and could make use of the ABS model. It is my wish to attract an array of collaborators on other types of brain and spinal cord injuries and pursue federal DoD and NIH grant funding in addition to my own personal interests with PTE.”

More broadly, Dr. Parsons hopes the simulator becomes a hub for related research at UF on a variety of brain conditions, including posttraumatic stress disorder, sleep disorders, or any complication that a soldier exposed to multiple IEDs might experience.

Friedlander waveform
An example of an ideal Friedlander wave. From: Ning Y-L, Zhou Y-G. Shock tubes and blast injury modeling. Chin J Traumatol. 2015;18(4):187-93. doi: 10.1016/j.cjtee.2015.04.005. Licensed under CC BY-NC-ND 4.0.

The ABS creates the shock wave by using a high-pressure helium tank to create pressure behind a membrane that is manually bolted into place between the driver and transition section. The pressure builds until the membrane ruptures, which sends a shockwave through the transition section of the ABS into the test section. The Friedlander wave forms in the test section, which is confirmed using dynamic and static pressure transducers. The shockwave then disperses in the final section of the ABS, the end-wave eliminator.

The simulator was designed by blast physicist David Ritzel (Dyn-Fx Consulting) and mechanical engineer Steve Parks (ORA Inc.), who both have more than 35 years of experience in the field. It is currently manufactured by Stumptown Research and Development LLC, which is based in Western North Carolina.

The ABS is unique compared to traditional cylindrical blast tubes and offers several advantages. A traditional blast tube that is 2.5 feet in diameter would need to be 50 feet long to create a simple Friedlander wave in the test section. But with the wedge-shaped driver of the ABS, the effect can occur faster and over a shorter distance in a much smaller simulator. In addition, the end-wave eliminator eliminates the artifacts found in the test section of open-ended traditional blast tubes.