USAMRDC Supports Development of Military Health System Auditory Blast Injury Prevention Standard
The U.S. Army Medical Research and Development Command's DOD Blast Injury Research Coordinating Office is overseeing a comprehensive reevaluation of the military's standards for protecting Warfighters, aiming to support a unified injury prevention standard that will reduce the risk of auditory injury in training and combat.
In support of auditory blast injury prevention, representatives from across the military, private industry, academia and medicine participated in the Blast Injury Prevention Standards Recommendation process, a multiyear consensus-building effort convened by BIRCO to recommend a standard for protecting people from hearing loss associated with exposure to the shock waves, called blast overpressure, caused by explosions and the firing of heavy weapons. The BIPSR process supports the recommendations of the Military Health System's Blast Injury Prevention Standards, which are biomedically valid descriptions of the physiological and biomechanical injury and performance responses of humans to blast overpressure.
Warfighters encounter blast overpressure in training as well as in combat. Blast overpressure can cause injury to many parts of the body, but unprotected ears are considered the most vulnerable. According to the Department of Veterans Affairs, tinnitus and hearing loss are the most prevalent service-related disabilities, affecting over 1.3 million veterans who received disability compensation in fiscal year 2020 alone. The VA estimates that compensation for hearing-related injuries totals over $1 billion annually.
"If each service is using its own auditory standard, it can be harder to conduct joint training exercises and joint operations," says Dr. Raj Gupta, BIRCO's deputy director. "The same injury occurs regardless of the service, so injury prevention should be the same."
Each service branch has implemented its own methods for protecting its Service Members from auditory injuries, but this fragmented approach has drawbacks.
As reported in a paper coauthored by Gupta in the November/December 2023 supplement to the scholarly journal Military Medicine, the subject matter experts participating in the BIPSR process evaluated 11 auditory injury protection standards of varying complexity currently in use in the United States and elsewhere against four criteria: usability, verification, validity of model design and validity of model results. The panel selected a methodology called the 8-hour Equivalent Level, which is a measure of the total amount of sound energy that a person is typically exposed to during an eight-hour period. This metric has been adopted in standards by the European Union, Australia, New Zealand and other countries, as well as by the National Institute for Occupational Safety and Health in the United States, as the preferred method for assessing the hazard posed by continuous noise.
"There was a lot of healthy debate," says Dr. Elizabeth Brokaw, a biomedical engineer and researcher with The MITRE Corporation, the technical lead for the BIPSR process and the lead author on the Military Medicine paper. "We used an iterative approach to build consensus, and it was great to see the group come together to understand the benefits and limitations of the different standards and address critical gaps in injury prevention."
The panel identified several knowledge gaps, including the lack of understanding of how the body's central nervous system is affected by noise and how to mitigate the effects of energy transmission through bone conduction, which can bypass hearing protection. The panel recommended conducting additional research to obtain data that will fill these and other identified knowledge gaps, to help support future research and development into technologies that can protect and heal injured Service Members. The panel has finalized its recommendations based on the current state of the science and is preparing to submit them to the Assistant Secretary of Defense for Health affairs for approval and action.
Auditory injury is one of 14 types of blast injury being evaluated by the MHS. When all the evaluations are complete, MHS will be able to provide comprehensive medical recommendations regarding blast injury prevention and standards to support the health of Service Members.
"It's very satisfying to be involved in the development of a standard that will lead to better protection from blast injuries," says Gupta. "At the end of the day, anything we can do to protect Service Members from hazards is worthwhile."