Comparison of kinetic changes during helicopter medical evacuations: civilian versus military flights.

BACKGROUND: Helicopter evacuation is crucial for providing medical care to casualties. Previous civilian studies have demonstrated that air transport can enhance survival rates compared with ground transport. However, there has been limited research on specific accelerations during helicopter flights, particularly in military flights. This study aims to analyse and compare the accelerations endured during civilian and military helicopter evacuations. METHODS: Accelerations were recorded during evacuation flights from the site of injury to the first medical responders in civilian helicopter EC135 T1, and military Puma SA.330 and Caiman NH90 TTH helicopters. The research investigated global acceleration and compared acceleration distributions along the vertical, lateral and longitudinal axes. A specific comparative study of the take-off phases was also performed. RESULTS: The analysis showed that vertical loads caused the most extreme accelerations for all types of helicopter but these extreme accelerations were rare and lasted for less than 1 s. Military flights show similar acceleration intensities to civilian flights, but accelerations are higher during short periods of the take-off phase. CONCLUSIONS: The findings suggest that helicopter evacuations during military operations are as safe as civilian evacuations and highlight the importance of patient positioning in the aircraft. However, further research should investigate the haemodynamic response to accelerations experienced during actual evacuation flights.

Effect of advanced rider assistance system on powered two wheelers crashes.

Advanced Rider Assistance Systems (ARAS) are solutions developed to reduce the crashes rate of Powered Two Wheelers (PTWs). They assist riders in their driving task by transmitting information on their environment or by automatically controlling the dynamics of their vehicle. This study describes a methodology for evaluating the impact of 14 ARAS on PTWs crashes. This methodology consists first of establishing links between ARAS functionalities and riders' failures in crashes situations. Then, an analysis of real crashes cases was conducted using two reals crashes databases: the "In-depth crashes investigation at the Laboratory of Accident Mechanisms Analysis (LMA)" in Salon-de-Provence, France, and the "Initiative for the Global harmonization of Accidents Data". A total of 390 crashes were analyzed. The results showed that ARAS had an influence on 61.5% of the crashes studied. ARAS benefits at the French national level were also assessed, with a weighting of the results obtained. In the French national data, the Anti-lock Braking System had the highest overall impact among the ARASs, estimated to have influenced 39.1% of crashes. Next, emergency braking systems influenced 30.1% of crashes, and an anti-collision warning system had an impact on 29.8% of crashes. This work provided an initial assessment of the most promising technologies for PTWs road safety. It could be used to guide industry and road safety policy towards the development of the most beneficial systems, and the introduction of standards or regulations.

The influence of achievement goals on objective driving behavior.

Investigating psychological characteristics through self-reported measures (e.g., anger, sensation seeking) and dynamic behaviors through objective measures (e.g., speed, 2D acceleration, GPS position etc.) may allow us to better understand the behavior of at-risk drivers. To assess drivers' motivation, the theoretical framework of achievement goals has been studied recently. These achievement goals can influence the decision-making and behaviors of individuals engaged in driving. The four achievement goals in driving are: seeking to improve or to drive as well as possible (mastery-approach), to outperform other drivers (performance-approach), to avoid driving badly (mastery-avoidance), and to avoid being the worst driver (performance-avoidance). Naturalistic Driving Studies (NDS) provide access to the objective measurements of data not accessible through self-reported measurements (i.e., speed, accelerations, GPS position). Three dynamic criteria have been developed to characterize the behavior of motorists objectively: driving events, time spent above acceleration thresholds (longitudinal and transversal), and the extent of dynamic demands. All these criteria have been measured in different road contexts (e.g., plain). The aim of this study was to examine the predictive role of the four achievement goals on these objective driving behaviors. 266 drivers (96 women, 117 men) took part in the study, and 4 242 482 km was recorded during 8 months. Simultaneously, they completed the Achievement Goals in Driving Questionnaire. The main results highlighted that mastery-approach goals negatively predicted hard braking and the extent of dynamic demands on plain and hilly roads. Mastery-approach goals seem to be the most protective goals in driving. Future research on the promotion of mastery-approach goals in driving may be able to modify the behavior of at-risk drivers.

Anthropometric characterization of the child liver.

PURPOSE: The major purpose of this retrospective study on 25 CT scans of child liver aged from 2 to 13 years was to investigate the growth, morphologic variations and modifications of the liver position as a function of the children age. The objective was to characterize the 3D geometry of the child liver, which is still unknown. METHODS: 3D reconstruction of child liver was performed using the Mimics(®) software. Measurements of volumes (total liver and right lobe), distances between anatomic reference points and angles were performed. The liver position was calculated with respect to the 11th thoracic vertebra. RESULTS: The liver shows a harmonious volume growth between the right and the left lobes, but a disharmonious one for the measurements in relation to the falciform ligament. The liver position, with respect to the vertebral column, in the peritoneal cavity was unchanged during the liver growth. CONCLUSION: The obtained results from this preliminary work give a description of the child liver during the growth and are of interest for the numerical modeling.

Anthropometric characterization of spleen in children.

PURPOSE: This paper aims to characterize the 3D geometry of the child spleen which is still unknown. METHODS: An anthropological measurement protocol, based upon 3D modeling using spleen-computed tomography data, was set up. Characteristic measurements were defined to allow dimensions and spatial localization description from classical anatomical landmarks (11th dorsal vertebra and 10th left rib). RESULTS: Growth patterns showed a global enlargement without significant changes in distance to anatomical bone points. CONCLUSIONS: This preliminary study describes a validated measurement protocol based on 3D reconstructions and gives description of the child spleen during growth.

Analysis of pre-crash characteristics of passenger car to cyclist accidents for the development of advanced drivers assistance systems.

The purpose of this study was to analyze car-to-cyclist accidents to determine the challenges for an active safety system on car to avoid accidents. Based on 2261 car-to-cyclist accidents provided by in-depth accident databases, accidents are analyzed more specifically from kinematic reconstructions. The main accident scenarios are determined: crossing nearside, crossing farside, longitudinal, turning (right and left) and others. Proportion of brakes activation by the drivers before the impact was also given for those scenarios. The relative positions of the cyclists to the vehicle are analyzed from few seconds before the impact until the crash. It is observed that one second before the impact most of the cyclists were at a lateral distance smaller than 5 m to the center line of the car and less than 20 m ahead of car front. Finally, the possible detection of the cyclist by implemented sensors in the vehicle and the possible triggering of an active safety system like an Automatic Emergency Braking or a Forward Collision Warning are studied. Required detection sensors parameters, such as Field Of View (FOV) and the detection range, were analyzed relatively to the scenario's characteristics, e.g. remaining time after cyclist appearance and before the collision, differences between scenario types. Different sensor FOVs and detection ranges were analyzed to determine their possible rates of cyclist detection. The study concluded that a FOV of 60° and a range of 35 m would detect most of the cyclists in car-to-cyclist accident scenarios. It was also concluded that in about 80% of cases, the last time to trigger brake (tLTTB), i.e. the last moment to brake in order to avoid the accident based on physical and comfort braking limitations by the car, was 1 s before the collision. It was also calculated that with a FOV of 60°, 51% of cyclists could be detected up to 4 s before tLTTB, and 72% up to 1 s before tLTTB. Values found in this paper can be useful to determine some of the specifications of an Advanced Driver Assistance System (ADAS), e.g. detection sensor coverages, available time to trigger an autonomous emergency braking or forward collision warning device. Those values are given for general ADAS sensors specification but also per scenario in the case of sensors that can adapt to a specific scenario.

Comparison of the biomechanical behavior of the liver during frontal and lateral deceleration.

BACKGROUND: The trunk of a car occupant can be injured by a frontal or lateral impact. Lesions can be either intrusion injuries or due to the effects of deceleration alone. The aim of this study conducted with human cadavers was to explore the effects of deceleration on the liver during frontal or lateral deceleration. METHODS: Trunks previously instrumented with accelerometers in three sites, the left and right lobes of the liver and the retrohepatic inferior vena cava, were subjected to substantial deceleration in three orientations: frontal, left, and right lateral. The anatomic consequences and deceleration data were measured. A deceleration ratio was defined as a peak deceleration measured in the liver divided by peak deceleration imposed on the trunk. RESULTS: Peak deceleration imposed on the trunks was up to 60 g, which caused peak deceleration up to 26 g in the liver. No anatomic injury was observed. For each orientation, deceleration ratios were not significantly different among the three sites (p = 0.64) or between left and right lateral decelerations (p = 0.12). Deceleration ratios were significantly different (p = 0.001) between frontal (3 sites combined) and lateral (3 sites of left and right lateral orientations combined) decelerations: 39.4% (+/-6) versus 48.4% (+/-11). CONCLUSIONS: In conclusion, at tested decelerations, under the hepatic injury threshold, cadaveric liver seemed to be subjected to higher deceleration when the trunk was decelerated in lateral than in frontal direction, without terminal impact.

Acquisition and analysis of road incidents based on vehicle dynamics.

Because motor vehicle crashes have decreased during the last decade in many countries in the world and are more diffuse, local authorities have difficulties to define road safety policies. An experiment with 51 cars of public fleets equipped with a specific Event Data Recorder was carried out in France during one year. The purposes of this research were to evaluate if incident data (critical driving situations) help to understand crashes, and to explore a new way for road infrastructure safety diagnosis. The analysis of 339 genuine incidents and 1237 simple events recorded illustrates the potentiality of such an experiment and provides: some insights about conditions in which incidents occur, a general overview of their distribution according to different road layouts, as well as information on the different levels of accelerations reached. It can be noticed that there is an overrepresentation of incidents in right curves compared to left curves. The simple events involving mostly the infrastructure could be used to detect road defects. Genuine incidents where the vehicle is subjected to important dynamic demands, related to potentially unsafe driving situations, can be used to improve knowledge of the motor vehicle crashes thanks to incident mechanisms analysis.

Issues and challenges for pedestrian active safety systems based on real world accidents.

The purpose of this study was to analyze real crashes involving pedestrians in order to evaluate the potential effectiveness of autonomous emergency braking systems (AEB) in pedestrian protection. A sample of 100 real accident cases were reconstructed providing a comprehensive set of data describing the interaction between the vehicle, the environment and the pedestrian all along the scenario of the accident. A generic AEB system based on a camera sensor for pedestrian detection was modeled in order to identify the functionality of its different attributes in the timeline of each crash scenario. These attributes were assessed to determine their impact on pedestrian safety. The influence of the detection and the activation of the AEB system were explored by varying the field of view (FOV) of the sensor and the level of deceleration. A FOV of 35° was estimated to be required to detect and react to the majority of crash scenarios. For the reaction of a system (from hazard detection to triggering the brakes), between 0.5 and 1s appears necessary.

Growth characterisation of intra-thoracic organs of children on CT scans.

This paper analyses the geometry of intra-thoracic organs from computed tomography (CT) scans performed on 20 children aged from 4 months to 16 years. The aim is to find the most reliable measurements to characterise the growth of heart and lungs from CT data. Standard measurements available on chest radiographies are compared with original measurements only available on CT scans. These measurements should characterise the growth of organs as well as the changes in their position relative to the thorax. Measurements were considered as functions of age. Quadratic regression models were fitted to the data. Goodness of fit of the models was then evaluated. Positions of organs relative to the thorax have a high variability compared with their changes with age. The length and volume of the heart and lungs as well as the diameter of the thorax fit well to the models of growth. It could be interesting to study these measurements with a larger sample size in order to define growth standards.

[Secular trends in anthropometrical measurements observed in three to 11-year-old French children between 1953 and 2005]. / Évolution séculaire des dimensions anthropométriques chez des enfants français âgés de trois à 11ans, entre 1953 et 2005.

This study covers a fifty-year period between 1953 and 2005 and looks at secular trends in stature, weight and sitting height sizes among French boys and girls between the ages of 3 and 11. A special modelling in function to the age and variable for each child was established so that a comparison could be made in the kinetic growth patterns over these same two periods. Statistical analysis shows a significant increase in growth, of 0.8cm per decade in stature, characterised by a certain increase in the lower limbs and the weight (0.8kg per decade) together with a proportional increase on the body mass index. Positive secular trends of this anthropometric nature are generally thanks to improved eating and sanitary habits and this study enables us to build and elaborate new standards in growth patterns essential for monitoring auxological development in 3 to 11-year-old children in the years 2000 and onwards.

The motorcyclist impact against a light vehicle: epidemiological, accidentological and biomechanic analysis.

This paper summarizes the results obtained within the framework of the French PROMOTO Project (PROtection of the MOTOrcyclist). The aim of this project was to analyze the impact between a motorcycle and a light vehicle from an epidemiological, accidentological and biomechanical point of view. The results have made it possible to outline the most frequent accident configurations such as the "turn on the left" and the most common injuries sustained by motorized two-wheelers (head and trunk). The biomechanic analysis has enabled a better understanding of the kinematics involved in an impact between a motorized two-wheeler and a light vehicle in various accident configurations (chronology and speed impact). While it is well known that motorcyclists frequently receive life threatening injuries to the head, spine and torso, this paper has been able to observe specific injury mechanisms such as pelvis impacts against the vehicle fuel tank and hyper-extension of the neck due to head impact on passenger cars.

Reproducibility of geometrical acquisition of intra-thoracic organs of children on CT scans.

This paper analyses geometry of intra-thoracic organs from computed tomography (CT) scans performed on 20 children aged from 4 months to 16 years. A set of two measurements on lungs and heart were performed by the same observer. A third set was performed by a second observer. Thus, the intra- and inter-observer relative deviation of measurements was analysed. Multiple regressions were used in order to study the relationship between the CT properties (scanner, voltage, dose, pixel size, slice increment) and the relative deviation of measurements. There is a very low systematic intra- and inter-observer bias in measurements except for the volume of the heart. None of the CT data properties has a significant influence on the relative deviation of measurement. In the present paper, the measurements and 3D reconstruction protocol described can be applied to characterise the growth of the intra-thoracic organs.

Child pedestrian anthropometry: evaluation of potential impact points during a crash.

This paper highlights the potential impact points of a child pedestrian during a crash with the front end of a vehicle. Child anthropometry was defined for ages between 3 and 15 years. It was based on the measurement of seven different segment body heights (knee, femur, pelvis, shoulder, neck, chin, vertex) performed on about 2,000 French children. For each dimension, the 5(th), 50(th) and 95(th) percentile values were reported, and the corresponding linear regression lines were given. Then these heights were confronted with three different vehicle shapes, corresponding to a passenger car, a sport utility vehicle and a light truck, to identify impact points. In particular, we show that the thigh is directly hit by the bumper for children above 12 years of age, whereas the head principally impacts the hood. The influence of child anthropometry on the pedestrian trajectory and the comparison with test procedures in regulation are discussed.

Posture and muscular behaviour in emergency braking: an experimental approach.

In the field of numerical crash simulations in road safety research, there is a need to accurately define the initial conditions of a frontal impact for the car occupant. In particular, human models used to simulate such impacts barely take into account muscular contracting effects. This study aims to quantify drivers' behaviour in terms of posture and muscular activity just before a frontal impact. Experiments on volunteers were performed in order to define these conditions, both on a driving simulator and on a real moving car. Brake pedal loads, lower limbs kinematics and muscle activation were recorded. Coupling instantaneous data from both experimental protocols (simulator versus Real car), a standard emergency braking configuration could be defined as (1) joint flexion angles of 96 degrees, 56 degrees and 13 degrees for the right hip, knee and ankle respectively; (2) a maximum brake pedal load of 780N; (3) a muscular activation of 55% for the anterior thigh, 26% for the posterior thigh, 18% for the anterior leg and 43% for the posterior leg. The first application of this research is the implementation of muscle tone in human models designed to evaluate new safety systems.

3D reconstruction of the diaphragm for virtual traumatology.

This study lies within the scope of passive road safety, and more particularly injury mechanisms of the abdominal area. The finite element modeling, which makes it possible to simulate a road accident and to observe the possible bone fractures or internal tissue injuries, allows large projections in the comprehension of injury mechanisms. However, the digital models already available and used in accidentology do not offer as one very simplified description of the diaphragm, as well for its geometry as for its bracing aspect and the modifications that this could induce in the behavior of abdominal organs and vessels at impact. In order to develop an accurate model of diaphragm for road safety research, a 3D reconstruction was performed, based on a sitting post-mortem Human subject sections. The resulting geometry was then turned into a segmented mechanical component (using the finite element method) and included in a full human model already available. The result is a valuable tool to improve the knowledge of injury mechanisms involved in car crashes at the abdominal level.

Biomechanic study of the human liver during a frontal deceleration.

BACKGROUND: Mechanisms of hepatic injury remain poorly understood. Surgical literature reports some speculative theories that have never been proved. The aim of this study was to examine the behavior of the liver during brutal frontal deceleration. METHODS: Six trunks, removed from human cadavers, underwent free falls at 4, 6, and 8 meters per second (mps). Accelerometers were positioned in the two lobes of the liver, in front of the vertebra L2, and in the retro hepatic inferior vena cava. Relative motions of the lobes of the liver and of the two other anatomic marks were observed. In parallel, numerical simulations of this experiment have been performed using a finite element model. RESULTS: In the direction of impact, the vertebra L2 had no considerable displacement with the inferior vena cava. There was a noteworthy displacement between the two hepatic lobes. The left hepatic lobe had a large relative displacement with the vertebra L2 and the inferior vena cava. The right hepatic lobe was more stable with the vertebra L2 and the inferior vena cava. Numerical simulation of the same protocol underlined a rotation effect of the liver to the left around the axis of the inferior vena cava. CONCLUSIONS: These results support the surgical data. They highlight a crucial zone and explain how dramatic lacerations between the two lobes of the liver can occur.

Tonic finite element model of the lower limb.

It is widely admitted that muscle bracing influences the result of an impact, facilitating fractures by enhancing load transmission and reducing energy dissipation. However, human numerical models used to identify injury mechanisms involved in car crashes hardly take into account this particular mechanical behavior of muscles. In this context, in this work we aim to develop a numerical model, including muscle architecture and bracing capability, focusing on lower limbs. The three-dimensional (3-D) geometry of the musculoskeletal system was extracted from MRI images, where muscular heads were separated into individual entities. Muscle mechanical behavior is based on a phenomenological approach, and depends on a reduced number of input parameters, i.e., the muscle optimal length and its corresponding maximal force. In terms of geometry, muscles are modeled with 3-D viscoelastic solids, guided in the direction of fibers with a set of contractile springs. Validation was first achieved on an isolated bundle and then by comparing emergency braking forces resulting from both numerical simulations and experimental tests on volunteers. Frontal impact simulation showed that the inclusion of muscle bracing in modeling dynamic impact situations can alter bone stresses to potentially injury-inducing levels.

An experimental cadaveric study for a better understanding of blunt traumatic aortic rupture.

BACKGROUND: Blunt traumatic aortic rupture (BTAR) is a common catastrophic injury leading to death. Considerable uncertainty remains regarding the pathogenic cause. This study examines the comportment of the heart and the aorta during a frontal deceleration. METHODS: Accelerometers were placed in the right ventricle of the heart, the aorta, the sternum, and the spine of six trunks removed from human cadavers. Different vertical decelerations were applied to cadavers and the relative motion of these organs was studied (19 tests). RESULTS: The deceleration recorded in the isthmus of the aorta was always higher that the one recorded in the heart (p < 0.05). The difference of deceleration was 17% and increased with the speed's fall (extremes 5-25%). There was no significant difference of deceleration between the bony structures of the thorax. These results experimentally demonstrate for the first time that the fundamental mechanism of BTAR is sudden stretching of the isthmus of the aorta. CONCLUSION: Four mechanisms are suspected to explain the location of the rupture: two hemodynamic mechanism (sudden increase of intravascular pressure and the water-hammer effect), and two physical mechanisms (sudden stretching of the isthmus and the osseous pinch). A greater understanding of the mechanism of this injury could improve vehicle safety leading to a reduction in its incidence and severity. Future work in this area should include the creation of an inclusive, dynamic model of computer-based modeling systems. This study provides for the first time physical demonstration and quantification of the stretching of the isthmus, leading to a computerized model of BTAR.