An Experimental Study On Recognization Of Early Lung Injury In Rat Model Of Pulmonary Blast Injury

ObjectivesTo explore and identify reliable indexes of early blast lung injury（BLI）in order to recognize early BLI by establishing early-stage（<48h）primary BLI model to record the early symptoms,arterial blood gas findings,changes of serum and lung tissue proinflammatory factors,and pathological manifestations of the lung in rats with BLI.MethodsA total of 40 SD rats were randomized into control group（C）,1h after the blast（B1h）,6h after the blast（B6h）,24h after the blast（B24h）and 48h after the blast（B48h）groups.Reduced tee and constant pressure pneumatics were used to simulate the blasting device and blast the chest only,followed by collection of early symptoms,analysis of arterial blood gas,measurement of wet/dry weight ratio（W/D）of lung tissues,serum and lung tissue homogenate tumor necrosis factor-α（TNF-α）,interleukin-6（IL-6）,vascular endothelial growth factor（VEGF）and neuropilin-1（NRP-1）data,and observation of pathological manifestations of lung tissue.SPSS19.0 statistical software was used for statistical analysis.Results1.Seven rats died instantly after the blast,the mortality was 17.9%（7/39）;there was no apparent injury in the chest;68.8%（22/32）manifested transient apnea;100%（32/32）manifested shallow and rapid breathing and gradually recovered after 6 hours;70.8%（17/24）manifested bradykinesia and reduced feeding in 6hours after blasting,which returned to normal in 24 hours.2.When compared with group C:In group B,lung tissue W/D ratio,serum IL-6concentration,lung tissue IL-6 concentration,serum NRP-1 concentration and lung tissue NRP-1 concentration increased（P values were 0.001,0.001,0.000,0.000and 0.000,respectively）;arterial oxygen pressure（PaO2）and lung tissue VEGF decreased（P values were 0.001 and 0.046,respectively）.3.Sub-group analysis results:When compared with group C:Lung tissue W/D ratio increased in group B1h（P=0.003）;PaO₂ slightly decreased in groups B1h,B6h,B24h and B48h（P values were 0.001,0.031,0.007 and 0.021,respectively）;serum IL-6 concentration increased in groups B1h,B24h and B48h（P value were 0.037,0.001 and 0.001,respectively）;serum NRP-1 concentration increased in group B6h（P=0.001）;lung tissue IL-6 concentration increased in groups B1h,B6h,B24h and B48h（P values were 0.000,0.000,0.000 and0.009,respectively）;lung tissue NRP-1 concentration increased in groups B1h,B6h and B24h（P values were 0.003,0.000 and 0.028,respectively）;lung tissue VEGF concentration decreased in groups B6h and B48h（P value were 0.004 and 0.046,respectively）.Among them,group B6h had the highest serum and lung tissue NRP-1 concentrations and the lowest VEGF concentration.4.Correlation analysis:In all rats with BLI,PaO₂ was negatively correlated with lung tissue W/D（r=-0.309,P=0.043）,lung injury scores were positively correlated with NRP-1 concentration in lung tissue（r=0.429,P=0.014）;in group B1h,PaO2was negatively correlated with lung tissue W/D（r=-0.680,P=0.032）;in group B6h,arterial blood pH was negatively correlated with lung tissue W/D（r=-0.713,P=0.024）,lung injury scores were negatively correlated with VEGF concentration in lung tissue（r=-0.769,P=0.013）,arterial blood pH was negatively correlated with serum IL-6 concentration（r=-0.798,P=0.042）;in group B24h,lung tissue W/D was positively correlated with serum IL-6（r=0.704,P=0.026）;in group B48h,lung injury scores were positively correlated with serum VEGF concentration（r=0.777,P=0.012）,lung tissue W/D was positively correlated with serum VEGF concentration（r=0.687,P=0.030）.5.Pulmonary interstitial vascular rupture,alveolar hemorrhage,alveolar epithelial cell and alveolar capillary injuries,accompanied by inflammatory cell infiltration,were the basic pathological changes of BLI.ConclusionsEarly-stage mild hypoxemia and changing patterns of serum and lung tissue IL-6,VEGF and NRP-1 help recognize early BLI and reflect the severity of lung injury.