In order to examine the feasibility of assessing blast event conditions from bone and to distinguish blast trauma from aircraft crash trauma, this study attempts to determine if the observations made in clinical research are mirrored in skeletal remains of individuals who died in blast events. Research was conducted by assessing the frequency of different forms of trauma and their comparison to aircraft crash trauma, the directionality of trauma, and open-air versus enclosed blast trauma. Data consisted of historic and forensic anthropology reports of individuals who died from blast events and aircraft crashes from the Defense POW/MIA Accounting Agency (DPAA). The results indicate a difference in the projectile/comminuted trauma between aircraft crash trauma and blast events, and that directionality is present in blast event fractures but should be used judiciously to determine blast direction. A sample of one open-air blast individual precluded assessment of enclosed versus open-air blast events.

One of the principal challenges of primary blast injury research is imitation of shock waves accurately and consistently in a safe and tunable platform. Existing simulators have been effective in these goals but have not been conducive for in vitro models due to their large size and air-mediated wave propagation. In this thesis, a redesigned benchtop shock wave generator (SWG) has provided a platform for in vitro models. A pulsed power generator charges a capacitor and discharges the capacitor through a bridge wire. The discharge causes the bridge wire to experience phase changes, momentarily becoming a gas or plasma. In this moment, the bridge wire expands radially and creates a pressure wave in the surrounding water. As the wave propagates, it forms a shock wave and strikes the cell platform at the far end of the conical tank. Current design efforts are focused on the tunability of the SWG, by varying the bridge wire material and diameter. Five materials at three bridge wire diameters have been tested. Each bridge wire was inserted into the SWG via a pinching mechanism. Either side of the pinching mechanism was connected to either terminal of the capacitor. When the pulsed power generator was cycled, the bridge wire was vaporized and generated a shock wave. A piezoelectric sensor near the wide end of the tank recorded the passing of the shock wave, which was used to derive various pressure metrics that correlate to injury. The sample size for each combination of diameter and material was five, with a grand total of seventy-five samples run. Two-way ANOVAs measuring the impacts of bridge wire material and diameter on a variety of shock wave metrics found that the diameter played a significant role in determining the peak overpressure and positive impulse generated while the main effect of material played a much smaller role. The interaction between material and diameter was also found to be significant. The tunable benchtop SWG provides a platform for exploration of primary blast injury using in vitro models. By adjusting the bridge wire diameter, the SWG can generate waves with a variety of shock wave metrics, providing an opportunity for researchers to address various degrees of injury. With the addition of this technology to the efforts to understand primary blast injury, development of treatments and protective equipment can be expedited. / Master of Science / Primary blast injury, the injury caused by the blast wave moving through the body, has been affecting those exposed to blast for nearly a century, since the regular use of conventional explosives in World War I. As equipment and war has changed in the past two decades, there has been heightened interest in understanding the effects of blast waves on the body. To assist in this research, blast wave simulators have been developed to recreate the blast wave in a controlled environment. However, current designs are not conducive to experiments on cultured cells. A new blast wave simulator, called the shock wave generator (SWG), has been designed as a platform for cultured cell-based experiments. The simulator generates a shock wave by exploding a thin bridge wire using high electrical current. The explosion occurs underwater, generating a shock wave capable of injuring cells at the opposite end of the tank. A platform such as this provides multiple opportunities to tune the pressure metrics related to the shock waves. Bridge wire material and volume play critical roles in the resulting shock wave, working together to define the amount of energy required to vaporize the bridge wire. Five materials and three diameters, a derivative of the wire volume, were investigated to determine their impacts on the resulting peak pressure, positive duration, and positive impulse. While wire material was not found to have a significant impact on peak pressure, wire diameter had a significant effect on the resulting overpressures. The thickest wire generated the lowest peak pressure while the thinner wires generated higher peak pressures. The thinner wires were not significantly different from one another. A similar result was found for positive duration and impulse. Overall, the use of an exploding wire to generate shock waves is applicable as an injury mechanism for cell cultures in primary blast injury research. This work along with future work will provide a tunable and controlled platform that has opened a new frontier for investigating the primary blast injury.

Injury from blast is significant in both military and civilian environments. Although injuries from blast are well-documented, the mechanisms of injury are not well understood. Developing better protection requires knowledge of injury mechanisms and material response to blast loading. The importance of understanding how soft materials such as foams and fabrics behave under blast loading is further apparent when one realizes the capacity for some of these materials, frequently used in protective ensembles, to increase the potential for injury under some conditions. The ability for material configurations to amplify blast pressure and injury has been shown experimentally by other researches, and numerically in this study. Initially, 1-D finite element and mathematical models were developed to investigate a variety of soft materials commonly utilized in ballistic and blast protection. Foams, which have excellent characteristics in terms of energy absorption and density, can be used in conjunction with other materials to drastically reduce the amplitude of the transmitted pressure wave and corresponding injury. Additionally, a more fundamental examination of single layers of fabric was undertaken to investigate to the effects of parameters such as fabric porosity and density. Shock tube models were developed and validated against experimental results from the literature. After the models were validated, individual fabric properties were varied independently to isolate the influence of parameters in ways not possible experimentally. Fabric permeability was found to have the greatest influence on pressure amplification. Kevlar, a ballistic fabric, was modelled due to its frequent use for fragmentation protection (either stand-alone or in conjunction with a hard ballistic plate). The developed fabric and foam material models were then utilized in conjunction with a detailed torso model for the estimation of lung injury resulting from air blast. It was found that the torso model predicted both amplification and attenuation of injury, and all materials investigated as a part of the study had the capacity for both blast amplification and attenuation. The benefit of the models developed is that they allow for the evaluation of specific protection concepts.

Injury from blast is significant in both military and civilian environments. Although injuries from blast are well-documented, the mechanisms of injury are not well understood. Developing better protection requires knowledge of injury mechanisms and material response to blast loading. The importance of understanding how soft materials such as foams and fabrics behave under blast loading is further apparent when one realizes the capacity for some of these materials, frequently used in protective ensembles, to increase the potential for injury under some conditions. The ability for material configurations to amplify blast pressure and injury has been shown experimentally by other researches, and numerically in this study. Initially, 1-D finite element and mathematical models were developed to investigate a variety of soft materials commonly utilized in ballistic and blast protection. Foams, which have excellent characteristics in terms of energy absorption and density, can be used in conjunction with other materials to drastically reduce the amplitude of the transmitted pressure wave and corresponding injury. Additionally, a more fundamental examination of single layers of fabric was undertaken to investigate to the effects of parameters such as fabric porosity and density. Shock tube models were developed and validated against experimental results from the literature. After the models were validated, individual fabric properties were varied independently to isolate the influence of parameters in ways not possible experimentally. Fabric permeability was found to have the greatest influence on pressure amplification. Kevlar, a ballistic fabric, was modelled due to its frequent use for fragmentation protection (either stand-alone or in conjunction with a hard ballistic plate). The developed fabric and foam material models were then utilized in conjunction with a detailed torso model for the estimation of lung injury resulting from air blast. It was found that the torso model predicted both amplification and attenuation of injury, and all materials investigated as a part of the study had the capacity for both blast amplification and attenuation. The benefit of the models developed is that they allow for the evaluation of specific protection concepts.

As explosive blasts continue to cause casualties in both civil and military environments, there is a need for increased understanding of the mechanisms of blast trauma at the organ level and a need for a more detailed predictive methodology. A fundamental understanding of blast injury will lead to the development of improved protective equipment and ultimately reduce the severity of injury. Models capable of predicting injury to varied blast loading will also reduce the emphasis on animal blast testing. To provide some historical context, this research was begun shortly after the U.S. led invasion of Iraq, and came to a close while there continues to be daily loss of life from blast injuries in the Middle East, as well as continued threats of terrorism throughout the world. In addition to industrial accidents, it is clear that blast injury is far more than just a military concern. Simplified finite element models of the human and sheep thoraces were created in order to provide practical and flexible models for the prediction of primary blast injury in simple and complex blast environments, and subsequently for the development of improved protective equipment. The models were created based on actual human and sheep geometries and published material properties. The fluid-structure interaction of the models compared well with experimental blast studies carried out during the course of the research, as shown by comparing actual and predicted overpressures in the free field and at the thorax. By comparing the models to published experimental data from simple blasts, trends in the results were verified and peak lung pressure was proposed as a trauma criterion. Local extent of injury in the lung is correlated to the peak pressure measured in each finite element, categorized as no injury (< 60 kPa), trace (60-100 kPa), slight (100-140 kPa), moderate (140-240 kPa) and severe (> 240 kPa). The calculation of the mean value of the peak lung pressures of all of the finite elements allows for an overall estimate of the injury level, with 35 kPa predicting threshold damage, 129 kPa for one percent lethality, and 186 kPa for fifty percent lethality. The simple blast results also compared well to the predictions of two previously validated mathematical models. Variation of predicted injury within a given loading severity was 15%, which is comparable to the model by Stuhmiller that had a variation of 20%. The model by Axelsson had very little variation (1.4%), but the differences between levels of severity were quite small, and often difficult to decipher. In addition to predicting consistent levels of injury, the finite element models were able to provide insight into the trauma mechanism, map the extent of injury through the lungs, and validate a local injury criterion. The models were then applied to predict injury under complex blast loading by subjecting the human finite element torso to a threshold level blast while located at varying distances from a wall or a corner. The results compared well to the validated mathematical models, showing a sharp increase in injury severity as the model approached the reflecting surface. When directly against the wall, the mean of the peak lung pressure values was 57 kPa, and in the corner, the mean value reached 69 kPa. Although these values did not reach the level representing one percent lethality, they do represent a significant increase in injury above threshold as a direct result of the surrounding geometry. Once again, the finite element models correctly showed injury trends and lung injury patterns reported in experiments. The models predicted the level of injury and were able to predict the time varying pattern of injury, which is something existing models cannot do. Having designed the models from physical principals, and having validated the models against published results, they can now be used in the continued development of protective equipment. Acknowledging that this model was the first iteration, the author believes that improvements in material properties, mesh refinement, and the investigation of other possible parameters for the prediction of injury will lead to substantial advances in the understanding of primary blast injury.

As explosive blasts continue to cause casualties in both civil and military environments, there is a need for increased understanding of the mechanisms of blast trauma at the organ level and a need for a more detailed predictive methodology. A fundamental understanding of blast injury will lead to the development of improved protective equipment and ultimately reduce the severity of injury. Models capable of predicting injury to varied blast loading will also reduce the emphasis on animal blast testing. To provide some historical context, this research was begun shortly after the U.S. led invasion of Iraq, and came to a close while there continues to be daily loss of life from blast injuries in the Middle East, as well as continued threats of terrorism throughout the world. In addition to industrial accidents, it is clear that blast injury is far more than just a military concern. Simplified finite element models of the human and sheep thoraces were created in order to provide practical and flexible models for the prediction of primary blast injury in simple and complex blast environments, and subsequently for the development of improved protective equipment. The models were created based on actual human and sheep geometries and published material properties. The fluid-structure interaction of the models compared well with experimental blast studies carried out during the course of the research, as shown by comparing actual and predicted overpressures in the free field and at the thorax. By comparing the models to published experimental data from simple blasts, trends in the results were verified and peak lung pressure was proposed as a trauma criterion. Local extent of injury in the lung is correlated to the peak pressure measured in each finite element, categorized as no injury (< 60 kPa), trace (60-100 kPa), slight (100-140 kPa), moderate (140-240 kPa) and severe (> 240 kPa). The calculation of the mean value of the peak lung pressures of all of the finite elements allows for an overall estimate of the injury level, with 35 kPa predicting threshold damage, 129 kPa for one percent lethality, and 186 kPa for fifty percent lethality. The simple blast results also compared well to the predictions of two previously validated mathematical models. Variation of predicted injury within a given loading severity was 15%, which is comparable to the model by Stuhmiller that had a variation of 20%. The model by Axelsson had very little variation (1.4%), but the differences between levels of severity were quite small, and often difficult to decipher. In addition to predicting consistent levels of injury, the finite element models were able to provide insight into the trauma mechanism, map the extent of injury through the lungs, and validate a local injury criterion. The models were then applied to predict injury under complex blast loading by subjecting the human finite element torso to a threshold level blast while located at varying distances from a wall or a corner. The results compared well to the validated mathematical models, showing a sharp increase in injury severity as the model approached the reflecting surface. When directly against the wall, the mean of the peak lung pressure values was 57 kPa, and in the corner, the mean value reached 69 kPa. Although these values did not reach the level representing one percent lethality, they do represent a significant increase in injury above threshold as a direct result of the surrounding geometry. Once again, the finite element models correctly showed injury trends and lung injury patterns reported in experiments. The models predicted the level of injury and were able to predict the time varying pattern of injury, which is something existing models cannot do. Having designed the models from physical principals, and having validated the models against published results, they can now be used in the continued development of protective equipment. Acknowledging that this model was the first iteration, the author believes that improvements in material properties, mesh refinement, and the investigation of other possible parameters for the prediction of injury will lead to substantial advances in the understanding of primary blast injury.

<p>Explosions are associated with more than 80% of the casualties in the Iraq and Afghanistan wars. Given the widespread use of thoracic protective armor, the most prevalent injury for combat personnel is blast-related traumatic brain injury (TBI). Almost 20% of veterans returning from duty had one or more clinically confirmed cases of TBI. In the decades of research prior to 2000, neurotrauma was under-recognized as a blast injury and the etiology and pathology of these injuries remains unclear.</p><p>This dissertation used the finite element (FE) method to address many of the biomechanics-based questions related to blast brain injuries. FE modeling is a powerful tool for studying the biomechanical response of a human or animal body to blast loading, particularly because of the many challenges related to experimental work in this field. In this dissertation, novel FE models of the human and ferret head were developed for blast and blunt impact simulation, and the ensuing response of the brain was investigated. The blast conditions simulated in this research were representative of peak overpressures and durations of real-world explosives. In general, intracranial pressures were dependent on the peak pressure of the impinging blast wave, but deviatoric responses in the brain were dependent on both peak pressure and duration. The biomechanical response of the ferret brain model was correlated with in vivo injury data from shock tube experiments. This accomplishment was the first of its kind in the blast neurotrauma field.</p><p>This dissertation made major contributions to the field of blast brain injury and to the understanding of blast neurotrauma. This research determined that blast brain injuries were brain size-dependent. For example, mouse-sized brains were predicted to have approximately 7 times larger brain tissue strains than the human-sized brains for the same blast exposure. This finding has important implications for in vivo injury model design, and a scaling model was developed to relate animal experimental models to humans via scaling blast duration by the fourth-root of the ratio of brain masses. </p><p>This research also determined that blast neurotrauma is correlated to deviatoric metrics of the brain tissue rather than dilatational metrics. In addition, strains in the blasted brain were an order-of-magnitude lower than expected to produce injury with traditional closed-head TBI, but an order-of-magnitude higher in strain rate. The 50th percentile peak principle strain metric of values of 0.6%, 1.8%, and 1.6% corresponded to the 50% risk of mild brain bleeding, moderate brain bleeding, and apnea respectively. These findings imply that the mechanical thresholds for brain tissue are strain-based for primary blast injury, and different from the thresholds associated with blunt impact or concussive brain injury because of strain rate effects.</p><p>The conclusions in this dissertation provide an important guide to the biomechanics community for studying neurotrauma using in vivo, in vitro, and in silico models. Additionally, the injury risk curves developed in this dissertation provide an injury risk metric for improving the effectiveness of personal protective equipment or evaluating neurotrauma from blast.</p> / Dissertation

Literature review: Background: Military-related stressors can adversely affect veterans’ mental health, in particular PTSD. This can have a detrimental impact on intimate relationships and family adjustment. To date, couple based interventions for PTSD and relational functioning in military couples have not been systematically reviewed. Objectives: This review summarises and synthesises literature investigating couple based interventions for PTSD and relational functioning in military couples. Method: A systematic review of all literature to date across 24 databases using an advanced combination of search terms. Ten studies were included (nine USA; one Australian). Results: A wide range of couple based interventions were identified: complementary and alternative therapies (CAM), sport and recreation programmes, retreats, courses as well as structured disorder focused couple therapies. There was preliminary evidence of support for couple based interventions treating PTSD, with relatively stronger support for disorder focused couple therapies over sports and recreation activities, CAM and retreats/courses. There was relatively little support for improved relational functioning assessed in couple based interventions treating PTSD. However, spouses tended to report a greater degree of improved relational functioning compared to veterans. Conclusions: There was relatively stronger evidence to support disorder focused couple therapies over other treatment modalities. However, there was a lack of robust designs used in effectiveness research of couple based interventions in military populations. There is potential for couple based interventions to be effective in treating PTSD in the UK military. Empirical study: Objective: Deployment to the armed conflicts in Afghanistan (Operation HERRICK/Enduring Freedom) and Iraq (Operation TELIC/Iraqi Freedom) can adversely affect the physical and mental health of those deployed. This study explored the association between traumatic brain injury (TBI), post-traumatic stress disorder (PTSD), the mediating effect of maladaptive emotional regulation strategies (MERS) and the effect of cause of injury (no injury, blunt force related or blast force related) in UK military veterans. Methods: 16 month longitudinal follow-up was conducted on a sample of 123 veterans (Murphy et al., 2015). Regression based secondary data analyses investigated the mediating effects of MERS (n=116) whilst correlational analyses explored the effect of injury mechanism on the relationship between TBI severity and PTSD severity (n=29). Results: Findings revealed support for the role of anger in mediating the effect that TBI severity had on PTSD severity. There was no support that the mechanism of injury was associated with greater reporting of psychological symptoms (anger, alcohol use or PTSD) or that MERS influenced the association between TBI severity and PTSD recovery at 16 month follow-up. Conclusion: Findings contribute to the understanding of how anger may underlie the relationship between TBI severity and PTSD severity, i.e., TBI severity was positively associated with PTSD scores and this effect operated due to increased TBI severity leading to higher rates of expressed anger which in turn increased PTSD symptoms. Future research using larger samples is required to further understand how the complicating factors of MERS and cause of physical injury affect outcome in veterans with co-occurring TBI and PTSD.

Explosives have become increasingly common on the battlefield worldwide. Military personnel and civilians often experience blast loading to the lower extremity due to its direct contact with the ground and floor of vehicles. The pressure and axial loading from these incidents often lead to detrimental injuries. These injuries can be due to a number of mechanisms terming them primary, secondary, tertiary, or quaternary blast injuries. Of these injuries, this study will focus on primary and tertiary injuries, specifically bone fractures, compartment syndrome, and soft tissue disruption which often result from blast loading due to these mechanisms. However, the pressure and load levels causing these injuries are unknown. Currently, the methodologies, which study the injury criteria and design of blast mitigating structures, are limited. The main limitations are the lower rates of testing (automobile), specimen limitation (cadavers, surrogates, etc.), cost, and testing repeatability. Consequently, the goal of this dissertation is to develop a realistic computational model which can be used to improve the injury criteria, personal protective equipment (PPE), and vehicular structure in a cost effective and timely manner. Three Aims were thus pursued. For Specific Aim 1, a standing lower extremity was developed, verified, and simulated with several open-air blast loading conditions. Specific Aim 2 focused on validating the lower extremity model using experimental drop tower test results. In the drop tower simulation, the lower extremity model was successfully converted into a seated posture model and setup with similar loading and boundary conditions as the experiment. Specific Aim 3 involved incorporating a boot into the standing lower extremity model and evaluating its ability to mitigate pressure waves. In summary, Specific Aims 1 and 2 developed, verified, and validated a realistic human lower extremity model for the use in blast simulations. Specific Aim 3 further confirmed the models use in developing PPE.

Blast-induced traumatic brain injury (bTBI) has been described as the defining injury of Operations Enduring Freedom and Iraqi Freedom (OEF/OIF). Previously, most blast injury research has focused on the effects of blast on internal, gas filled organs due to their increased susceptibility. However, due to a change in enemy tactics combined with better armor and front-line medical care, bTBI has become one of the most common injuries due to blast. Though there has been a significant amount of research characterizing the brain injury produced by blast, a sound understanding of the contribution of each component of the shockwave to the injury is needed. Large animal models of bTBI utilize chemical explosives as their shockwave source while small animal models predominantly utilize compressed air-driven membrane rupture as their shockwave source. We designed and built a multi-mode shock tube capable of utilizing compressed gas (air or helium)-driven membrane rupture or chemical explosives (oxyhydrogen – a 2:1 mixture of hydrogen and oxygen gasses, or RDX – high order explosive) to produce a shockwave. Analysis of the shockwaves produced by each mode of the McMillan Blast Device (MBD) revealed that compressed air-driven shockwaves exhibited longer duration positive phases than compressed helium-, oxyhydrogen-, or RDX-driven shockwaves of similar peak overpressure. The longer duration of compressed air-driven shockwaves results in greater energy being imparted on a test subject than would be imparted by shockwaves of identical peak overpressures from the other sources. Animals exposed to compressed air-driven shockwaves exhibited more extensive brain surface hematoma, more blood-brain barrier compromise, more extensive reactive astrocytosis, and greater numbers of activated microglia in their brains than did animals exposed to oxyhydrogen-driven shockwaves of even greater peak overpressure. Taken together, these data suggest that compressed air-driven shockwaves contain more energy than their chemical explosive-derived counterparts of equal peak overpressure and can result in greater injury in an experimental animal model. Additionally, these data suggest that exposure to longer duration shockwaves, which is common in certain realworld scenarios, can result in more severe bTBI. The results of this study can be used to aid design of blast wave mitigation technology and future clinical intervention.