| Helicopter has a good maneuverability with a high accident rate,resulting in a large number of injuries and deaths for the pilot and occupants.Regarding helicopter crash-induced injury,most literature aimed at analyzing the epidemiological data and few studies were done using experimental research.In addition,few previous experimental research often focus on cadaver,computer simulation or dummy collision,of which models were lack of physiological responses.The injury patterns of the driver and occupants involved in the crashes were still unknown until present.Our experiment were carried out from the platform of biological crash equipment,using adult minipig to via claudo-cephalad(vertical)decelaration impacts(CCDI),and determine the injury patterns of helicopter crashed.Materials and MethodsPart one: The injury patterns of animal suffered helicopter vertical impact:Twenty-one Congjiang minipigs were used in this part.Eighteen adult Congjiang minipigs were randomly divided equally into Group I and II,three as control group.A modified deceleration sled equipment were designed.Configured impact velocity was 8m/s in Group I,and 11m/s in Group II.Dynamical response process of impact was recorded by a high-speed camera.Vital signs,arterial blood gas analysis(ABGA)and neurons system damage markers were acquired before,immediately after impact and every hour thereafter.Pathological alternations of thoracoabdominal organs were examined in case of animal death or within 6hrs following impact.Two animals in each group were selected randomly and performed CT-scan.All animals were dissected at 6hr post injury and the injuries were evaluated according to Abbreviate Injury Score(AIS)and Injury Severe Score(ISS).Part two: The biomechanical response of animal suffered helicopter vertical impact: Fourteen adult animals were randomly equally divided into two groups.Five transducers were implanted in animals under anesthetized: 2acceleration transducers in skull and pelvis,and 3 pressure transducers in intracranial,lumbar cistern and abdomen,respectively.A total of 14 impact tests were performed using the modified deceleration sled equipment at the configured speed for the animals at8 m/s in Group I,and 11m/s in Group II.After impact,responses of sensors(acceleration and pressure)were recorded and analyzed.Part three: Performing DOE(Design of Experiment)using Minitab?Rfor three factors including environmental,direction and falling speed,in which a aviation digital human model mimicking the pilot was used in MADYMO?R(v6.22).The crashes of DOE was simulated and calculated MADYMO?Rsoftware.Numeric predicted HIC36,Angular-Y and Nij were used to analyze the factors associated with head and neck injury under 8m/s and 11m/s in different environmental and direction impact.ResultsPart one: Thoracoabdomen deformed greatly during impacting,while the extent and duration of deformation were greater in Group? than that in Group?.All animals survived in Group I,and in Group II all died of spleen rupture-induced massive bleeding within 2hrs following impact.Result of ABGA suggested no respiratory failure in both groups.Injuries to thoracoabdominal organs were observed as follow:(1)spleen rupture(Group?:n=9 vs.Group?:n=9);(2)fracture of axial skeleton(Group?:n=9 vs.Group?:n=9);(3)pulmonary hemorrhage(Group?:n=2 vs.Group?:n=8);(4)subendocardial hemorrhage(SEH,Group?:n=4 vs.Group?:n=1);(5)subcapsular hematoma of kidney(Group?:n=0 vs.Group?:n=1).Maximal AIS of thorax in Group I and II were 4(Group?:n=1)and 5(Group?:n=8),respectively,while that of abdomen were 5 in both groups(Group?:n=8 vs.Group?:n=9).ISS in Group II was 52.71±6.13,which was significantly higher than that in Group I,26.67±5.02(p<0.05).Part two: The maximum accelerated(Amax)of sled was 21.27±1.70 g in Group?,and 34.07±13.56 g in Group?,respectively.The maximum vertical acceleration determined of pelvis in two groups were 108.92±58.87 g and 139.13±78.54 g,and Amax of head in two groups were28.17±10.87 g and 47.41 ± 28.54 g.The maximum pressures(Pmax)of CSF(median sulcus)in two groups were 15.34±4.28 kpa and 34.93±9.84 kpa,in lumbar cistem were130.49±128.73 kpa and 267.34±137.99 kpa,respectively.The Pmax in abdomen of two groups were 41.24±16.89 kpa and 63.61±65.83 kpa.Part three: The risk assessment of head and neck injury of passenger suffered helicopter vertical impact: Head linearacceleration peak were 133.97 g,102.54 g and 27.26 g in the soft,hard and ideal ground under the impact velocity was 11m/s,respectively.And Angular-Y were 2582.9rad/s2 in soft and hard ground.Angular-Y was 2075.9rad/s2 in ideal ground.Angular-Y were2019.6rad/s2 in soft and hard ground under the velocity of 8m/s.And Angular-Y was1566.5rad/s2 in ideal ground.When the helicopter crashed the impact velocity of 11 m/s in soft ground and hard ground,the range of Angular-Y were between 2549.4rad/s2and3412.6rad/s2,and Nij between 0.88256 and 1.07100.When the helicopter crashed the impact velocity of 8 m/s in iadeal ground,the range of Angular-Y were between1566.5rad/s2 and 2562.3rad/s2,the maximal Nij was 0.83706.ConclusionsMultiple injuries in thoracoabdomen organs were observed in the pigs sustained CCDI,in which injury to spleen,axial skeleton and lung were injured more frequently.The most important factor in the animal to death was hemorrhagic shock caused by spleen repute.Liver ruptures,rib fracture were not detected in our experiment.With an increase of the impact velocity,the peak values of each transducer and organ injuries were increased,and it decays along z-axis.This study replicated the helicopter accident animal model in two degrees: 8m/s with severe,not life-threatening and 11m/s with sever,life-threatening.The acceleration of two groups were(108.92±58.87)g and(139.13±78.54)g.Environment,velocity and direction have influence of head a neck injury under helicopter crashed.Pilot have a high ris risk of head and neck that helicopter crashed in a non-ideal ground with a damage energy absorption equipment under the velocity of 11 m/s.The pilot to take upright sitting position can reduces the risk of neck injury.This study produced the animal model of severe injury and threaten-life injury mimicking the injuries sustained by the pilot involved in helicopter drop accidents,concluded the relationship between injury severity and impact velocity,and analyzed clearly the injury factors of head and neck injury under helicopter crashed.The results of this experiment may be usefull to improve treatment and prevention against the injuries induced by helicopter crashes. |
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