Casualty Safe Ride Standards: A Study of Ride-induced Blood Clot Dislodgement and Related Soft Tissue Studies
Abstract
During transport from the battlefield to the field hospital casualties are subject to various forces. Potential risks due to these forces are largely unknown, but may include exacerbating injuries sustained in the theater. Therefore, safe ride standards should beestablished that limit these forces to safe physiological limits. In our work, we submit that one potential transport risk is transport-induced dislodgement (i.e., embolization) of blood clot from the site of injury; thus, leading to deadly sequelae such as heartattacks, strokes, and pulmonary embolisms. The objective of this work is to determine safety standards for the transport of casualties based on risk of blood clot dislodgement. To this end, we will address two fundamental challenges: Challenge 1) We must identifythe direct #loads# that lead to clot dislodgement, where #loads# describes not only a load magnitude but also a load frequency, direction, rate, etc. In other words, clots can dislodge under various loading conditions such as due to single hard and fast shocks, or repeated low-magnitude loads. Challenge 2) We must identify how the direct loads experienced by the clot depend on the external loads on the body, i.e., external loads will likely be dampened by the viscoelastic properties of the tissue-surrounding vessel and clot. To address the first challenge, we will conduct in-vitro mechanical experiments. Thereby, we will determine the fracture toughness of blood clot under quasi-static and dynamic loading and under fatigue conditions. We will do so to test both external loading scenarios, e.g., via mode-I fracture tests, and internal loading scenarios, e.g., via cavitation-induced fracture. To address the second challenge, we will build high-fidelity finite element models of the human leg and quantify the load transfer function between leg-external accelerations and the loads the clot experiences. We will validate our models against measurements on instrumentalized human legs. Once validated, our finite element model will serve as a virtual test bed to predict clot loads based on transportation profiles. In addition to addressing Challenges 1 & 2, we will also conduct two related soft tissue studies. First, we will quantify themechanical (and specifically the fracture) properties of four other soft tissues: brain, liver, kidney, and spleen. To this end, wewill use similar methods as developed for our blood clot studies. Second, we will also optimize blood clot composition and coagulation parameters to match the mechanical properties of four soft tissues: again brain liver, kidney, and spleen. Thereby, we will transform blood clot into a soft tissue mimic that is inexpensive, easy to make, and accurate. Our addressing of Challenges 1 & 2 will be a critical step toward establishing safe ride standards. Thereby, our work will positively impact the DoD by providing safer casualty transport. Furthermore, the results of our additional studies will positively impact the DoDby providing data on human tissue behavior that can for example be used in optimizing protective gear.*Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 29, 2023
- Source ID
- N000142312575
Entities
People
- Manuel K Rausch
Organizations
- Office of Naval Research
- United States Navy
- University of Texas at Austin