An explosion typically lasts only a fraction of a second, but the damage to the human body can be much more far-reaching.
Statistics indicate that a large number of military veterans—as well as firefighters, police officers, and others—experience hearing loss and tinnitus, or a ringing in the ears, from noise exposure in the line of duty. For veterans, auditory damage caused by exposure to blasts and loud noises can bring with it a range of other health impairments, like balance issues, respiratory disease, anxiety and depression, and even neurocognitive decline, research indicates.
"Significant balance problems, postural difficulties, and falls are some of the main reasons that veterans seek health care," said Suhrud Rajguru, professor of biomedical engineering and otolaryngology-head and neck surgery at the University of Miami. "That's why we are looking at how blast exposure affects hearing, balance, and outcomes. All of these affect their quality of life, and that's why we are seeking solutions to mitigate the negative consequences of noise exposure."
Rajguru is leading an interdisciplinary team of researchers from the College of Engineering and the Miller School of Medicine who are studying the impact of explosions on human health, some of which may come from the pressure exerted on the body during a blast. To do that, Rajguru and Dr. Michael Hoffer, professor of otolaryngology, as well as Dr. Pavan Krishnan, a medical resident in otolaryngology, and Yuan Gao, a neuroscience doctoral student, developed a simulated explosion model to understand the impacts of this exposure. They are now using it in preclinical models to understand how blasts affect health.
"After any blast, we know that 98 percent of veterans report problems with balance—such as dizziness and other symptoms—immediately, and many report a constellation of related issues months and years afterward," said Krishnan. "It's a very understudied area, and we have limited understanding of how to diagnose and manage the ensuing vestibular dysfunction."
But Rajguru knows the effects of experiencing a blast aren't limited to hearing and balance. Since hearing loss is linked to dementia and related cognitive disorders, such as Alzheimer's disease, the blast model also allows them to learn more about the relationship between hearing and brain function. Therefore, the team is also working with Nadine A. Kerr, assistant professor of neurological surgery, W. Dalton Dietrich, director of The Miami Project to Cure Paralysis, and Helen Bramlett, professor of neurological surgery, to unravel how explosions can impact cognition. And they are also working with aerosol scientist Chang-Yu Wu, professor and chair of the Department of Chemical, Environmental, and Materials Engineering, to determine the impacts on the lungs from these wartime experiences.
"Hearing loss is one of the biggest risk factors for neurocognitive decline and dementia, and veterans face an increased risk of cognitive decline and dementia due to various factors unique to their military service," added Rajguru, who is also a faculty member of The Miami Project to Cure Paralysis. "Our collaborative studies with Dr. Kerr in a preclinical model predisposed to Alzheimer's disease potentially allows us to parallel what happens in human subjects."
The team's work is funded by the U.S. Department of Defense, along with the U.S. DEVCOM Army Research Laboratory, and the U.S. Department of Veterans Affairs. All of these agencies recognize the strong prevalence of balance difficulties in veterans today.
The team also knows their work could help others beyond the veteran population. While there are drugs being developed to counteract hearing damage and loss, Rajguru's laboratory has pioneered cooling (or mild therapeutic hypothermia) as a solution for auditory damage and tinnitus. Toward that goal, Rajguru's startup RestorEar Devices LLC developed devices that deliver this hypothermia therapy to help prevent or reduce noise-induced hearing loss, as well as devices that prevent damage to the sensitive inner ear structures from surgical interventions. These devices and applications of hypothermia are now undergoing clinical trials.
"Overall, we are studying how all these multi-organ injuries caused by explosions—whether it's through the inner ear, or the lungs or brain—how that can affect patients in the long run," Rajguru said. "We are looking at cooling as a therapy, but also how the novel drugs that we are developing in our labs can be applied to prevent or reverse some of these damages. And this wouldn't be feasible without the multidisciplinary team at the University of Miami and our collaborators across departments."
