Development of head injury assessment reference values based on NASA injury modeling.
ABSTRACT NASA is developing a new crewed vehicle and desires a lower risk of injury compared to automotive or commercial aviation. Through an agreement with the National Association of Stock Car Auto Racing, Inc. (NASCAR®), an analysis of NASCAR impacts was performed to develop new injury assessment reference values (IARV) that may be more relevant to NASA's context of vehicle landing operations. Head IARVs associated with race car impacts were investigated by analyzing all NASCAR recorded impact data for the 2002-2008 race seasons. From the 4015 impact files, 274 impacts were selected for numerical simulation using a custom NASCAR restraint system and Hybrid III 50th percentile male Finite Element Model (FEM) in LS-DYNA. Head injury occurred in 27 of the 274 selected impacts, and all of the head injuries were mild concussions with or without brief loss of consciousness. The 247 noninjury impacts selected were representative of the range of crash dynamics present in the total set of impacts. The probability of head injury was estimated for each metric using an ordered probit regression analysis. Four metrics had good correlation with the head injury data: head resultant acceleration, head change in velocity, HIC 15, and HIC 36. For a 5% risk of AIS≥1/AIS≥2 head injuries, the following IARVs were found: 121.3/133.2 G (head resultant acceleration), 20.3/22.0 m/s (head change in velocity), 1,156/1,347 (HIC 15), and 1,152/1,342 (HIC 36) respectively. Based on the results of this study, further analysis of additional datasets is recommended before applying these results to future NASA vehicles.
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ABSTRACT: The objective of this study was to investigate new methods for predicting injury from expected spaceflight dynamic loads by leveraging a broader range of available information in injury biomechanics. Although all spacecraft designs were considered, the primary focus was the National Aeronautics and Space Administration Orion capsule, as the authors have the most knowledge and experience related to this design. The team defined a list of critical injuries and selected the THOR anthropomorphic test device as the basis for new standards and requirements. In addition, the team down-selected the list of available injury metrics to the following: head injury criteria 15, kinematic brain rotational injury criteria, neck axial tension and compression force, maximum chest deflection, lateral shoulder force and displacement, acetabular lateral force, thoracic spine axial compression force, ankle moments, and average distal forearm speed limits. The team felt that these metrics capture all of the injuries that might be expected by a seated crewmember during vehicle aborts and landings. Using previously determined injury risk levels for nominal and off-nominal landings, appropriate injury assessment reference values (IARVs) were defined for each metric. Musculoskeletal deconditioning due to exposure to reduced gravity over time can affect injury risk during landing; therefore a deconditioning factor was applied to all IARVs. Although there are appropriate injury data for each anatomical region of interest, additional research is needed for several metrics to improve the confidence score. - See more at: http://journal.frontiersin.org/Journal/10.3389/fbioe.2014.00004/full#sthash.0ed5bMcj.dpufFrontiers in Bioengineering and Biotechnology 03/2014; 2. DOI:10.3389/fbioe.2014.00004
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ABSTRACT: Currently, NASA occupant protection standards are primarily based on the Multi-axial Dynamic Response Criteria, which NASA refers to as the Brinkley Dynamic Response Criterion (BDRC). The BDRC was developed by the United States Air Force (USAF) and adopted by NASA in the mid-1990s during the development of the Assured Crew Return Vehicle (ACRV) and evaluation of the Soyuz three-person crew vehicle landing impact tests. The BDRC criteria includes a dynamic model, which is used to evaluate the risk of injury using a series of lumped parameter models with mass, spring, and damping properties. The individual model units are arranged orthogonally to respond to linear accelerations and linear components of angular accelerations measured on the vehicle occupant seat. During the BDRC development, these model responses were related to human injury data to develop low, medium, and high injury risk limits. Because of the simplicity of the BDRC, it is very attractive to designers, as it is very simple to evaluate for many design cases with only seat accelerations. However, because of these simplifications and the specific characteristics of the seating systems used, there are application criteria or rules that are necessary to correctly apply the model and interpret the results. In addition, because of the subjects used in the development of the BDRC and some unique considerations for NASA’s applications, several limitations have been identified that limit the injury prediction capabilities of the model. The purpose of this document is to review the BDRC development, document the rules necessary to apply the BDRC, identify limitations for NASA’s application, and describe additional testing and analysis methods necessary to supplement the BDRC.
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ABSTRACT: In the management of sports-related concussion, little is known about the effect of wearing or not wearing a helmet (i. e., helmet status) on the acute outcomes of concussed athletes. We endeavored to assess acute neurocognitive and symptom changes after SRC in helmeted vs. unhelmeted athletes. In a retrospective study, 1 025 athletes from 2 regional databases sustained a SRC. Athletes were matched by age, gender, number of prior concussions, and days to post-concussion test, yielding a final cohort of 138 athletes. For each group of 69, differences in post-concussion neurocognitive and symptom scores were compared using group mean differences as well as reliable change index (RCI) scores set at the 80% confidence interval. With gender, prior concussions, and days to post-concussion test similar in each group, using group mean change scores and RCI methodology, we found no significant differences between the helmeted and unhelmeted groups in 4 neurocognitive tests and one total symptom score. In a cohort of carefully matched athletes from 2 regional concussion centers, helmet status was unrelated to neurocognitive scores and total symptoms in athletes after suffering a SRC. These findings suggest that acute outcomes in helmeted vs. unhelmeted sports are quite similar. © Georg Thieme Verlag KG Stuttgart · New York.International Journal of Sports Medicine 02/2015; 36(05). DOI:10.1055/s-0034-1395587 · 2.37 Impact Factor