Study On The Characteristics And Early Detection Methods Of Severe Lung Blast Injury

Background:Explosive injuries are common in military conflicts,terrorist attacks and industrial and agricultural safety production accidents.It is easy to have a large number of wounded,seriously run on medical resources,and improve the passing rate of explosive injuries,which is of great significance to improve the treatment rate of explosive wounded.The injury caused by shock wave on the body is called blast injury,which is the primary injury mechanism of explosion injury.Lung is a common target organ of blast injury,and lung blast injury is the most common among all primary blast injuries.The mechanism of lung blast injury is complicated,strong occult,often compound burn and fragment injury,early diagnosis and identification is difficult,easy to cause serious consequences due to missed diagnosis.In the past half a century,based on the research and analysis of military conflicts,explosion accidents,animal experiments and other data,some scoring tools and treatment guidelines for blast injuries have been put forward at home and abroad,such as based on the 6-hour treatment intervention associated with prognostic risk of military combat injury scale,but there is a lack of evidence-based medicine and animal experimental evidence,especially in the plateau environment.At present,although there are many detection methods for respiratory diseases,the clinical evaluation of severe lung blast injury is mostly based on CT images,and the detection efficiency of mass explosion injuries is low,especially in the classification of blast injuries.Animal experiments mainly rely on pathological anatomy,and there are some problems in the connection between the results and clinical pathophysiological diagnosis,but the research on early detection of severe lung blast injury at high altitude is still blank.Therefore,first of all,through the summary and analysis of typical cases of blast injury,we try to sort out the deficiency in the early detection and classification of lung blast injury and the need for injury classification.Secondly,on the basis of BST-I platform,pigs similar to human anatomy and pathophysiology of trauma were used as experimental subjects to control the experimental parameters to establish lung blast injury models with different levels of injury.24-hour clinical parameters were detected to study the physiological and pathological evolution of animal models of different grades of lung blast injury,and to compare injury severity score（ISS）and concise injury score(abbreviated injury scale（AIS）,organ injury score（OIS）,MCIS,pathologic severity scale of lung blast injury（PSSLBI）,blast lung injury severity score（BLISS）and other international standards to comprehensively determine the injury grade,and select the multimodal methods and parameters for early injury assessment.Finally,under the condition of real explosion in the outfield,the sheep with similar mechanical threshold of pulmonary blast injury and easy to control in the outfield were used as the experimental subjects,and the model of severe lung blast injury in goats was established in batches under the condition of static explosion in the outfield,verify the means of early examination.Objectives:Analyze the clinical characteristics and treatment outcome of a large number of casualties in typical major explosion accidents,sort out the technical bottlenecks to be solved in the early four-stage examination of severe lung blast injury,and study the characteristics and dynamic evolution of blast injury in large animals under laboratory conditions.the multimodal indexes for early identification of severe lung blast injury were screened and verified in the static explosion test of live ammunition in the outfield.Methods:1.Analysis of typical cases of explosive injuryThe gas explosion accident occurred in a county of China was analyzed retrospectively,and the early treatment data such as early injury assessment,injury grading and injury controlled resuscitation were summarized to explore the deficiency of severe blast injury in early examination and treatment and the demand of pathophysiological examination index.2.Study on the characteristics and multimodal identification of severe lung blast injury under laboratory conditionsTwenty-six Panamanian Xiang pigs were injured by large biological shock tube（BST-I）.The vital signs,blood gas analysis,pulmonary ultrasound and hemodynamics were collected before and 24 hours after injury.The central electrical monitoring parameters were collected automatically by 5min after injury.The animals were killed and the anatomical and pathological scores were taken after observation.3.Study on the verification of examination method of severe lung blast injury under the condition of field explosionExperiment 1:Twenty goats were randomly divided into 3m group（n=4）,4 m group（n=7）,5 m group（n=5）and 6 m group（n=4）.8kg TNT equivalent new explosives were used to injure goats under plain conditions.The vital signs（body temperature,heart rate,respiratory rate,blood pressure）,arterial blood gas and lung gross anatomy were observed before injury,0.5h and 3h after injury,respectively.The wet/dry weight ratio of lung tissue was measured,.Experiment 2:Twenty-eight healthy goats were randomly divided into two groups 3m group（n=22）and 3.5m group（n=6）.Primary lung blast injury was caused by new 8kg TNT equivalent explosive from 2800m to 4600m above sea level.the vital signs（body temperature,heart rate,respiration,blood pressure）,arterial blood gas and pulmonary ultrasound were collected before and 3 hours after injury.The clinical manifestation and survival were observed.After 3 hours of observation after injury,it was transferred to the 2800-meter experimental site.And 24 hours later,the goats were killed for anatomy and lung wet to dry weight ratio.Results:1.Analysis of typical cases of explosive injuryAs a result of the accident,16 people were killed on the spot,and 10 survived and received rapid examination,triage,transportation and effective treatment.the mortality rate of blast injury was as high as 61.54%.One person died 11 days after severe craniocerebral blast injury,and one person was discharged from hospital because of recurrence of primary underlying disease.3 patients still had varying degrees of hearing loss at discharge,and 1patient was accompanied by paroxysmal tinnitus.4 cases were improved and discharged from hospital.The death rate of a large number of injured in explosion accident is extremely high,and the injury condition of explosion is complex,but the method of early examination is limited and single at present,while the incidence and fatality rate of lung injury in explosion accident are high,and the injury progress is rapid.it is necessary to identify the injury condition in time and monitor the changes of injury in order to prevent irreparable death caused by secondary and severe craniocerebral injury.2.Study on the characteristics and multimodal identification of severe lung blast injury under laboratory conditionsThe animal model of graded lung blast injury was made.the injury was caused by the closure of the blind end of the biological shock tube.the animal anatomy showed that the injury of the right lung was more severe than that of the left lung,and the dorsal lung was more severe than the abdomen.Based on the multimodal monitoring parameters of lung blast injury,we evaluated the injury of 26 large animals,including 9 severe and above lung blast injury,with a mortality rate of 33.33%≤1h and 55.56%≤6h,and 6 moderate lung blast injury and 6 mild lung blast injury.5 pigs in the blank control group survived more than 24hours.0.5h after severe lung blast injury,heart rate（p<0.05）increased,drop in mean arterial pressure（p<0.05）,shock index（p<0.05）increased,oxygen saturation（p<0.05）decreased,The ejection blood volume per beam（p<0.05）decreased,peripheral vascular resistance index（p<0.05）increased,global end diastolic volume index（p<0.05）decreased,partial pressure of arterial oxygen（p<0.001）decreased,partial pressure of arterial blood carbon dioxide（p<0.005）increased.Extravascular lung water index（p<0.01）、pulmonary vascular permeability index（P<0.01）increased,oxygenation index（P<0.01）decreased and pulmonary ultrasonography score were（P<0.001）increased.In severe lung blast injury,there was a time-dependent correlation between pulmonary ultrasound score with HR（R=0.74,p<0.01）、OI（R=-0.83,p<0.001）,ELWI（R=0.83,p<0.001）、PVPI（R=0.76,p<0.001）、Sp O₂（R=-0.62,p<0.01）、SI（R=0.55,p<0.05）、Aa DO₂（R=-0.53,p<0.05）、ITBI（R=-0.68,p<0.01）;3 hours after injury,shock index AUC=0.80（95%CI:0.59-1,p<0.05）,heart rate AUC=0.82（95%CI:0.61-1,p<0.05）,oxygenation index AUC=0.81（95%CI:0.63-1,p<0.05）have good detection ability for moderate and above lung blast injury.There was a time-effect relationship in the prediction of moderate and more moderate lung blast injury.The predicted values at 0.5h,3h and 6h after injury were AUC=0.73（95%CI:0.53-0.94,p>0.05）,AUC=0.93（95%CI:0.82-1,p<0.001）and AUC=0.93（95%CI:0.82-1,p<0.001）y.Lung ultrasound score AUC=0.96（95%CI:0.86-1,p<0.01）and oxygenation index AUC=0.90（95%CI:0.75-1,p<0.01）could predict the severity of severe blast injury 3 hours after injury.3.Study on the verification of examination method of severe lung blast injury under the condition of field explosionExperiment 1:The animal model of severe lung blast injury in plain was made.There were 4 goats with severe lung blast injury and above,all of them were 3 meters group,the mortality rate of≤15min was 25%,and the rest of the animals survived more than 24 hours;7 goats had moderate lung blast injury,the mortality rate of<24 hours was 28.57%;and 9goats with mild lung blast injury survived more than 24 hours.Severe blast before versus 0.5h after injury heart rate（117.75±16.02）bpm vs.（101±17.58）bpm,mean arterial pressure（108.67±4.61）mm Hg vs.（111.13±11.04）mm Hg,partial pressure of arterial oxygen（75.2±9.60）mm Hg vs.（52.00±32.05）mm Hg,arterial partial pressure of carbon dioxide（32.2±5.45）mm Hg vs.（61.00±52.66）mm Hg,before injury versus 3 hours after injury heart rate（117.75±16.02）bpm vs.（114.00±46.67）bpm,mean arterial pressure（108.67±4.61）mm Hg vs.（117.00±15.56）mm Hg,partial pressure of arterial oxygen（75.2±9.60）mm Hg vs.（74.00±12.73）mm Hg,partial pressure of arterial carbon dioxide（32.22±5.45）mm Hg vs.（30.50±0.57）mm Hg.Clinical signs:persistent respiratory distress and increased airway secretion occurred immediately after injury,and severe lung blast injury often showed primary metabolic acidosis with respiratory alkalosis and respiratory distress.No trauma,hemorrhage,damage,fracture and so on were found in the severe lung blast injury in the plain,but there were varying degrees of injury to the gas-containing hollow organs,such as pulmonary hemorrhage,gastrointestinal hemorrhage and edema,rupture of tympanic membrane and so on.Experiment 2:The animal model of severe lung blast injury at high altitude was made.There were 28 goats with severe lung blast injury and above.The mortality rates of≤15min and≤30min were 42.86%and 57.14%.The other 12 animals survived for more than 24 hours.Severe blast injury in 4600m before compare with 1h after injury heart rate（117.3±27.98）bpm vs.（108.79±33.75）bpm,mean arterial pressure（124.27±25.89）mm Hg vs.（115±32.68）mm Hg,partial pressure of arterial oxygen（34±3.29）mm Hg vs.（43.33±11.95）mm Hg,partial pressure of arterial carbon dioxide（28.1±1.39）mm Hg vs.（24.8±3.01）mm Hg.In 4600m before compare with 3 hours after injury heart rate（117.3±27.98）bpm vs.（114.36±31.87）bpm,mean arterial pressure（124.27±25.89）mm Hg vs.（122±35.97）mm Hg,Partial pressure of arterial oxygen（34±3.29）mm Hg vs.（37.72±15.77）mm Hg,Arterial carbon dioxide partial pressure（28.1±1.39）mm Hg vs.（25.98±7.56）mm Hg.Clinical signs:respiratory distress,mental malaise,shivering,mouth,eye and nose bleeding,cough,hiccup,closed rib fracture and so on immediately after injury.Pulmonary ultrasonography can find abnormal signs in the early stage of severe lung blast injury at high altitude.Conclusion:The incidence of lung blast injury is high and the injury is serious,so it is urgent to improve the efficiency of early detection of lung blast injury.The indexes such as heart rate,mean arterial pressure,shock index,oxygenation index and pulmonary ultrasonography have good differentiation in 3 hours of moderate and severe lung blast injury,and can meet the requirement of 6 hours of disability in moderate and severe war injury.The animal experiments of outfield explosion show that the series of indexes we have established can meet the detection of blast injury of lung in the field,but the characteristics and time window of explosion injury at high altitude are different from those in the plain,which need to be further verified.