Computational modeling of blast-induced traumatic brain injury

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 105-113).Blast-induced TBI has gained prominence in recent years due to the conflicts in Iraq and Afghanistan, yet little is known about the mechanical effects of blasts on the human head; no injury thresholds have been established for blast effects on the head, and even direct transmission of the shock wave to the intracranial cavity is disputed. Still less is known about how personal protective equipment such as the Advanced Combat Helmet (ACH) affect the brain's response to blasts. The goal of this thesis is to investigate the mechanical response of the human brain to blasts and to study the effect of the ACH on the blast response of the head. To that end, a biofidelic computational model of the human head consisting of 11 distinct structures was developed from high-resolution medical imaging data. The model, known as the DVBIC/MIT Full Head Model (FHM), was subjected to blasts with incident overpressures of 6 atm and 30 atm and to a 5 m/s lateral impact. Results from the simulations demonstrate that blasts can penetrate the intracranial cavity and generate intracranial pressures that exceed the pressures produced during impact; the results suggest that blasts can plausibly directly cause traumatic brain injury. Subsequent investigation of the effect of the ACH on the blast response of the head found that the ACH provided minimal mitigation of blast effects. Results from the simulations conducted with the FHM extended to include the ACH suggest that the ACH can slightly reduce peak pressure magnitudes and delay peak pressure arrival times, but the benefits are minimal because the ACH does not protect the main pathways of load transmission from the blast to brain tissue. A more effective blast mitigation strategy might involve altering the helmet design to more completely surround the head in order to protect it from direct exposure to blast waves.by Michelle K. Nyein.S.M

Computational modeling of primary blast effects on the human brain

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from department-submitted PDF version of thesis.Includes bibliographical references (p. 155-167).Since the beginning of the military conflicts in Iraq and Afghanistan, there have been over 250,000 diagnoses of traumatic brain injury (TBI) in the U.S. military, with the majority of incidents caused by improvised explosive devices (IEDs). Despite the urgent need to understand blast-induced TBI in order to devise strategies for protection and treatment, much remains unknown about the mechanism of injury, the effects of personal protective equipment (PPE) such as helmets, and injury metrics and thresholds. In order to help address these gaps, this thesis has four objectives: 1) to present a comprehensive computational framework for investigating the mechanical response of the human head to blasts that includes blast-structure interaction codes, a detailed, three-dimensional model of a human head generated from high-resolution medical imaging data, and an experimentally-validated constitutive model for brain tissue; 2) to validate the framework against a broad range of experiments, including free-field blast tests involving physical human head surrogates and laboratory-scale shock tube tests involving animals and human cadavers; 3) to use the computational framework to investigate the effect of PPE on the propagation of stress waves within the brain following blast events and evaluate their blast protection performance; and 4) to develop interspecies scaling laws for the blast response of the brain that would allow translation of injury metrics from animals to humans.by Michelle K. Nyein.Ph.D

Porcine Head Response to Blast

Recent studies have shown an increase in the frequency of traumatic brain injuries related to blast exposure. However, the mechanisms that cause blast neurotrauma are unknown. Blast neurotrauma research using computational models has been one method to elucidate that response of the brain in blast, and to identify possible mechanical correlates of injury. However, model validation against experimental data is required to ensure that the model output is representative of in vivo biomechanical response. This study exposes porcine subjects to primary blast overpressures generated using a compressed-gas shock tube. Shock tube blasts were directed to the unprotected head of each animal while the lungs and thorax were protected using ballistic protective vests similar to those employed in theater. The test conditions ranged from 110 to 740 kPa peak incident overpressure with scaled durations from 1.3 to 6.9 ms and correspond approximately with a 50% injury risk for brain bleeding and apnea in a ferret model scaled to porcine exposure. Instrumentation was placed on the porcine head to measure bulk acceleration, pressure at the surface of the head, and pressure inside the cranial cavity. Immediately after the blast, 5 of the 20 animals tested were apneic. Three subjects recovered without intervention within 30 s and the remaining two recovered within 8 min following respiratory assistance and administration of the respiratory stimulant doxapram. Gross examination of the brain revealed no indication of bleeding. Intracranial pressures ranged from 80 to 390 kPa as a result of the blast and were notably lower than the shock tube reflected pressures of 300–2830 kPa, indicating pressure attenuation by the skull up to a factor of 8.4. Peak head accelerations were measured from 385 to 3845 G’s and were well correlated with peak incident overpressure (R2 = 0.90). One SD corridors for the surface pressure, intracranial pressure (ICP), and head acceleration are presented to provide experimental data for computer model validation

An animal-to-human scaling law for blast-induced traumatic brain injury risk assessment

Despite recent efforts to understand blast effects on the human brain, there are still no widely accepted injury criteria for humans. Recent animal studies have resulted in important advances in the understanding of brain injury due to intense dynamic loads. However, the applicability of animal brain injury results to humans remains uncertain. Here, we use advanced computational models to derive a scaling law relating blast wave intensity to the mechanical response of brain tissue across species. Detailed simulations of blast effects on the brain are conducted for different mammals using image-based biofidelic models. The intensity of the stress waves computed for different external blast conditions is compared across species. It is found that mass scaling, which successfully estimates blast tolerance of the thorax, fails to capture the brain mechanical response to blast across mammals. Instead, we show that an appropriate scaling variable must account for the mass of protective tissues relative to the brain, as well as their acoustic impedance. Peak stresses transmitted to the brain tissue by the blast are then shown to be a power function of the scaling parameter for a range of blast conditions relevant to TBI. In particular, it is found that human brain vulnerability to blast is higher than for any other mammalian species, which is in distinct contrast to previously proposed scaling laws based on body or brain mass. An application of the scaling law to recent experiments on rabbits furnishes the first physics-based injury estimate for blast-induced TBI in humans.United States. Army Research Office. Institute for Soldier Nanotechnologies (Contract DAAD-19-02-D-0002

Are there any changes in burden and management of communicable diseases in areas affected by Cyclone Nargis?

<p>Abstract</p> <p>Background</p> <p>This study aims to assess the situation of communicable diseases under national surveillance in the Cyclone Nargis-affected areas in Myanmar (Burma) before and after the incident.</p> <p>Methods</p> <p>Monthly data during 2007, 2008 and 2009 from the routine reporting system for disease surveillance of the Myanmar Ministry of Health (MMOH) were reviewed and compared with weekly reporting from the Early Warning and Rapid Response (EWAR) system. Data from some UN agencies, NGOs and Tri-Partite Core Group (TCG) periodic reviews were also extracted for comparisons with indicators from Sphere and the Inter-Agency Standing Committee.</p> <p>Results</p> <p>Compared to 2007 and 2009, large and atypical increases in diarrheal disease and especially dysentery cases occurred in 2008 following Cyclone Nargis. A seasonal increase in ARI reached levels higher than usual in the months of 2008 post-Nargis. The number of malaria cases post-Nargis also increased, but it was less clear if this reflected normal seasonal patterns or was specifically associated with the disaster event. There was no significant change in the occurrence of other communicable diseases in Nargis-affected areas. Except for a small decrease in mortality for diarrheal diseases and ARI in 2008 in Nargis-affected areas, population-based mortality rates for all other communicable diseases showed no significant change in 2008 in these areas, compared to 2007 and 2009. Tuberculosis control programs reached their targets of 70% case detection and 85% treatment success rates in 2007 and 2008. Vaccination coverage rates for DPT 3^rddose and measles remained at high though measles coverage still did not reach the Sphere target of 95% even by 2009. Sanitary latrine coverage in the Nargis-affected area dropped sharply to 50% in the months of 2008 following the incident but then rose to 72% in 2009.</p> <p>Conclusion</p> <p>While the incidence of diarrhea, dysentery and ARI increased post-Nargis in areas affected by the incident, the incidence rate for other diseases and mortality rates did not increase, and normal disease patterns resumed by 2009. This suggests that health services as well as prevention and control measures provided to the Nargis-affected population mitigated what could have been a far more severe health impact.</p

Profile of long COVID symptoms needing rehabilitation: a cross-sectional household survey of 12,925 SARS-CoV-2 cases between July and December 2021 in Bangladesh

Background and aims : It is important to determine the profile of long COVID (LC) symptoms within the scope of rehabilitation in Bangladesh. This study’s objective was to estimate the newly experienced long COVID symptoms needing rehabilitation by determining the prevalence and spectrum of impairments due to LC in Bangladesh. Methods A Cross-sectional household survey of 12,925 COVID-19 patients confirmed by RT-PCR from 24 testing facilities in Bangladesh. LC was diagnosed according to WHO working group definition. COVID-19 Yorkshire Rehabilitation Scale (C19-YRS) was used to determine the symptom responses, symptom severity, new long COVID symptoms, and scope of rehabilitation. Results The population proportion of LC symptoms requiring rehabilitation interventions are 0.22 [95% CI, 0.20–0.24] in Bangladeshi people diagnosed with SARS-CoV-2. Among them, 0.08 [95% CI, 0.07–0.09] had mild, 0.07 [95% CI, 0.06–0.09] had moderate, and 0.05 [95% CI, 0.04–0.06] had severe long COVID symptoms (LCS). There was a significant positive correlation between LCS and functional disabilities (r=0.889, p<0.001), while a negative correlation was observed between the severity of symptoms and overall health (r=-0.658, p<0.001). In comparison to the pre-COVID status, 17 new LCS were observed and the increase in the scope of rehabilitation intervention among LCS ranged between 0.01 [95% CI, 0.001–0.01] and 0.21 [95% CI, 0.19–0.22]. In Bangladesh, 59% (n=334) of the LC cases are out of reach for any rehabilitation interventions. Conclusion Nearly one-fourth of Bangladeshi Post-COVID-19 have long COVID (LC). Seventeen symptoms (LCS) were observed and more than half of the populations having long COVID are out of reach of any rehabilitation facilities

Influence of handler relationships and experience on health parameters, glucocorticoid responses and behaviour of semi-captive Asian elephants

Declining wild populations combined with accumulating captive populations of e.g. livestock, pets, draught and zoo animals have resulted in some threatened species with substantial proportions of their populations in captivity. The interactions animals have with humans in captivity depend on handler familiarity and relationship quality and can affect animal health, growth and reproduction with consequences for the success of conservation programmes. However, assessments of how specific human–animal relationships affect a range of physiological and behavioural outcomes are rare. Here, we studied semi-captive Asian elephants with detailed records of elephant–handler (mahout) relationships and veterinary management, allowing assessment of multiple welfare indicators in relation to specific mahout–elephant relationship lengths and mahout experience. These included measures of physiological stress (faecal glucocorticoid metabolite [FGM], heterophil:lymphocyte ratio [H:L]), muscle damage (creatine kinase [CK]), immunological health (total white blood cell count [TWBC]) and behaviour (response to mahout verbal commands). We found no evidence that FGM or H:L related to aspects of the mahout–elephant relationship. Longer overall mahout experience (i.e. years of being a mahout) was linked to increased muscle damage and inflammation, but the lengths of specific mahout–elephant relationships were inversely associated with muscle damage in working-age elephants. Elephants responded more to familiar mahouts in behavioural tasks and faster to mahouts they had known for longer. In summary, our results found little evidence that the mahout–elephant relationship affects physiological stress in this population based on FGM and H:L, but mahout experience and relationships were linked to other physiological responses (CK, TWBC), and elephants require behavioural adjustment periods following mahout changes. Key words: Animal welfare, glucocorticoids, human–animal interactions, human–animal relationships, mahout, physiology</p

Behavioral responses of terrestrial mammals to COVID-19 lockdowns

COVID-19 lockdowns in early 2020 reduced human mobility, providing an opportunity to disentangle its effects on animals from those of landscape modifications. Using GPS data, we compared movements and road avoidance of 2300 terrestrial mammals (43 species) during the lockdowns to the same period in 2019. Individual responses were variable with no change in average movements or road avoidance behavior, likely due to variable lockdown conditions. However, under strict lockdowns 10-day 95th percentile displacements increased by 73%, suggesting increased landscape permeability. Animals' 1-hour 95th percentile displacements declined by 12% and animals were 36% closer to roads in areas of high human footprint, indicating reduced avoidance during lockdowns. Overall, lockdowns rapidly altered some spatial behaviors, highlighting variable but substantial impacts of human mobility on wildlife worldwide.acceptedVersio