Study On Application Of Ultrasound In The Rabbit Model Of Acute Lung Injury And Acute Respiratory Distress Syndrone

ObjectiveWe used the self-made metal hammer to blow the chest of New Zealand rabbits,exploring the optimal crackdown to successfully establish the lung contusion induced acutelung injury model of rabbits. All the rabbits in this study were blow the same region of thechest. The successful lung contusion induced acute lung injury model of rabbits could lay thefoundation for the ultrasound evaluation of the hemodynamic changes of rabbits after acutelung injury.Method24New Zealand white rabbits were randomly divided into3groups, namely1strikegroup,2strike group,3strike group, with8rats in each group. Each group of rabbits wereexecuted tracheal intubation after hit, then connected to a ventilator for mechanical ventilation,maintaining the fraction of inspired oxygen (FiO2)50%during ventilation. Each group ofrabbits remained in the left femoral artery, for measuring partial pressure of oxygen in arteryblood (PaO2). After24h,48h,96h we observed the lung injury of rabbits through CT andultrasound respectively, at the same time, we measured the partial pressure of oxygen inartery blood through the indwelling tube remained in femoral artery.ResultsAfter24h,48h,96h,1strike group’s observation of the lungs showed no significantchanges. After24h, the observation of2strike group of the lungs’ condition did not changesignificantly. After48h,2strike group’s observation of the lungs showed acute lung injury,CT imaging showed relatively small patchy opacities, blowing lesions of the lung tissue showed diffuse comet tail sign in ultrasound, after96h, the observation performed as the bigshape fuzzy shadow in CT, in ultrasound the range of blowing lesions of the lung tissueperformed as diffuse comet tail syndrome expanded than the range in48h.3strike group’srabbits showed rib fractures, pneumothorax, and respiratory distress, then coughed sputumpink foam, finally all died.1strike group’s PaO2/FiO2>400,24h of2strike group’s PaO2/FiO2>400,48h and96h of2strike group’s PaO2/FiO2<300.ConclusionsThe2attack is the more appropriate crackdown for the establishment of rabbit acutelung injury and acute respiratory distress syndrome model induced by blunt chest injury. After48h and96h, the rabbit models’ lungs showed acute lung injury. And96h’s effect was moreobvious. The3attack easily caused rib fractures, pneumothorax, and rapidly emergingrespiratory distress and then died. So the3attack was not appropriate for modeling. PART ⅡCOMPARISON BETWEEN POSITIVE END EXPIRATORYPRESSURE MEASURED BY ULTRASONIC ASSESSMENT ANDLOWER INFLECTION POINT MONITORED BY PRESSUREVOLUME CURVEObjectiveThrough the comparison between positive end expiratory pressure (PEEP) measured byultrasonic assessment and lower inflection point (LIP) monitored by pressure volume (P-V)curve, investigated the value of PEEP measured by ultrasonic assessment guiding lungrecruitment.Method24New Zealand rabbits were successfully established a rabbit model of acute lung injury,then connected to the ventilator for mechanical ventilation by pressure control mode, settingthe tidal volume as6ml/kg, the respiratory rate gradually reducing to8times per minute, therespiratory ratio as1.5:1, the FiO2maintaining50%during whole ventilation. Under themaintenance of mechanical ventilation, we set the PEEP, at the beginning the PEEP set as0,increasing1cmH2O per level. At the same time, using ultrasound observed the recruitmentcondition of the subpleural consolidation, and we stopped adding PEEP until the subpleuralconsolidation of lung tissue to achieve complete recruitment, then we recorded the PEEP atthis time. This is the PEEP value measured by ultrasonic assessment. Each experiment wasoperated at least2different consolidation region of pulmonary. The average value of PEEPwas the final PEEP value obtained by the ultrasonic. Under the maintenance of machineryventilation, ALI rabbits were performed endotracheal intubation and connected with the threeway pipe. One end of the three tube connected to a ventilator, the other end connected withsyringe of50ml, the final end connected to the pressure gauge. Each time we injected5ml airto the rabbit lung by syringe, while the pressure changes through the pressure meter detectinglung volume. We stopped injected air to the rabbit lung until the pressure increasing obviously.The obtained data were used to draw the P-V curve using Excel software. Finally we coulddetermine the LIP according to the P-V curve.Results21cases of the24ALI/ARDS rabbits were observed that at least one subpleuralpulmonary consolidations could be detected in the entire respiratory cycle.70consolidationsof lung tissue from21cases of ALI/ARDS rabbits were brought into next analysis.70 consolidations of lung tissue completely recruited under the PEEP ventilation. The PEEPobtained by ultrasound is always greater than the corresponding pressure value of LIP. AfterLIP+2cmH2O, also only1case reached the PEEP level obtained by ultrasound. Throughstatistical analysis, PEEP was positively correlated with LIP, the correlation coefficientr=0.885(p<0.01).ConclusionsThe PEEP measured by ultrasound assessment can guide the lung recruitment in acutelung injury rabbits, and can provide reference for treatment to patients of acute lung injury,especially to the severe patients. PART ⅢINFLUENCE OF POSITIVE END EXPIRATORY PRESSUREOBTAINED BY ULTRASONIC ON HEMODYNAMICS OF ACUTELUNG INJURY RABBIT INDUCED BY BLUNT CHEST INJURYObjectiveThrough detection of hemodynamic indexes of acute lung injury rabbits using ultrasonic,investigated the effect of PEEP (obtained by ultrasound) ventilation on hemodynamics ofacute lung injury rabbits induced by thoracic contusion injury.Method24New Zealand rabbits were established as ALI/ARDS model made by blunt chestinjury, then we obtained PEEP by ultrasonic method respectively, following all theALI/ARDS rabbits obtained PEEP (obtained by ultrasound) ventilation. During the processwe detected the heart rate (HR), pulmonary arterial systolic pressure (PASP), cardiac outputof right heart (CORH), cardiac output of left output heart (COLH), ejection fraction (EF%) ofthe rabbits, before and after mechanical ventilation. PASP was assessed according to thepressure of three tricuspid’s regurgitation. Each index was measured by the same personbefore and after mechanical ventilation. Each measurement was obtained in3differentheartbeat cycle measured and then averaged. Finally, analyses the changes of these indexes bystatistical method.ResultsCompared with the indexes before PEEP ventilation, after PEEP ventilation HR, CORHincreased, and the difference has statistically significant (p<0.05); PASP, COLH and EF%hadno obvious changes, and has no significant difference (p>0.05).ConclusionsThe ventilation using PEEP monitored by ultrasound method can relieve hemodynamiceffects of ALI/ARDS rabbits induced by blunt chest injury, and mainly by improving thefunction of right heart.