Marine Mammal Lung Dynamics when Exposed to Underwater Explosion Impulse

The dynamic response of human lungs due to underwater shock wave exposure

Since the 19th century, underwater explosions have posed a significant threat to service members. While there have been attempts to establish injury criteria for the most vulnerable organs, namely the lungs, existing criteria are highly variable due to insufficient human data and the corresponding inability to understand the underlying injury mechanisms. This study presents an experimental characterization of isolated human lung dynamics during simulated exposure to underwater shock waves. We found that the large acoustic impedance at the surface of the lung severely attenuated transmission of the shock wave into the lungs. However, the shock wave initiated large bulk pressure-volume cycles that are distinct from the response of the solid organs under similar loading. These pressure-volume cycles are due to compression of the contained gas, which we modeled with the Rayleigh-Plesset equation. The extent of these lung dynamics was dependent on physical confinement, which in real underwater blast conditions is influenced by factors such as rib cage properties and donned equipment. Findings demonstrate a potential causal mechanism for implosion injuries, which has significant implications for the understanding of primary blast lung injury due to underwater blast exposures.

Human lung simulants subjected to underwater explosions - An experimental investigation

An experimental investigation was performed on human lung simulants to evaluate their response to an underwater explosive blast. The artificial lungs were instrumented with sensors to record changes in the internal pressure and strains for a specimen with and without a surrounding ribcage. The lungs were to-scale models representative of a 50th-percentile male. The experiments were performed using 65.5 mg of explosive charge placed 0.5 m from the lungs in an 8,200-liter water tank. The tank was instrumented with blast transducers and high-speed cameras to measure the pressure from the explosive charge and record the lung deformation history through high-speed images and digital image correlation. Results showed a significantly delayed response to the underwater blast due to the lungs' inertia. In addition, the lung response was indifferent to its orientation relative to the shock direction. The lungs initially contracted after the underwater shock and then expanded, showing a 50% change in relative volume, from minimum to maximum volume, over a 7 ms duration. Results and observations qualitatively relate to the types of injuries observed during preexisting case studies.

Mysticetes to MiniConference to Manuscripts: Introduction to Thematic Issue on Mysticete Anatomy

This issue of the Anatomical Record is focused on the theme of Mysticete Anatomy. There are six included articles that explore the anatomy of the nasal region (Marquez et al., 2018; Maust-Mohl et al., 2018), larynx (Damien et al., 2018), lungs (Fetherston et al., 2018), sublingual fascia (Werth et al., 2018), and brain (Raghanti et al., 2018). These papers document anatomical features exhibited by mysticetes (baleen whales) and their related cousins (including other whales, and the semiaquatic moose and hippopotamus). This theme stems from a 2-day MiniConference on Mysticete Anatomy, hosted at the Icahn School of Medicine at Mount Sinai in New York City on May 2016. Anatomy is explored in the contexts of function and evolution of aquatic adaptations. Anat Rec, 2019. © 2019 Wiley Periodicals, Inc. Anat Rec, 302:663-666, 2019. © 2019 Wiley Periodicals, Inc.