Prevention of Blast-induced Auditory Injury Using 3D Printed Helmet and Hearing Protection Device - A Preliminary Study on Biomechanical Modeling and Animal

Abstract

Introduction: Repeated blast exposures result in structural damage to the peripheral auditory system (PAS) and the central auditory system (CAS). However, it is difficult to differentiate injuries between two distinct pathways: the mechanical damage in the PAS caused by blast pressure waves transmitted through the ear and the damage in the CAS caused by blast wave impacts on the head or traumatic brain injury. This article reports a preliminary study using a 3D printed chinchilla "helmet" as a head protection device associated with the hearing protection devices (e.g., earplugs) to isolate the CAS damage from the PAS injuries under repeated blast exposures.

Materials and methods: A finite element (FE) model of the chinchilla helmet was created based on micro-computed tomography images of a chinchilla skull and inputted into ANSYS for FE analysis on the helmet's protection against blast over pressure. The helmet was then 3D printed and used for animal experiments. Chinchillas were divided into four cases (ears open, with earplug only, with both earplug and helmet, and with helmet only) and exposed to three blasts at blast over pressure of 15 to 20 psi. Hearing function tests (e.g., auditory brainstem response) were performed before and after blast on Day 1 and Days 4 and 7 after blasts.

Results: The FE model simulation showed a significant reduction in intracranial stress with the helmet, and the animal results indicated that both earplug and helmet reduced the severity of blast-induced auditory injuries by approximately 20 dB but with different mechanisms.

Conclusions: The biomechanical modeling and animal experiments demonstrated that this four-case study in chinchillas with helmet and hearing protection devices provides a novel methodology to investigate the blast-induced damage in the PAS and CAS.