Effects Of Heliox Mechanical Ventilation On Rabbit With HCL-induced Acute Lung Injury

Objective: To research the effect and mechanism of Heliox mechanical ventilation onrabbit with HCL-induced acute lung injury by using multiple methods.Methods:30healthy male New Zealand white rabbits were randomly divided intothree groups,with10in each group.Normal control group(group A): the rabbits wereinjected the0.9%sodium chloride injection2ml/kg into the endotracheal intubationafter tracheotomy, then absorbed pure oxygen5min to discharge nitrogen, given50%air-oxygen mixture gas to mechanical ventilation in the end;Injury group(group B):the rabbits were injected PH=1HCL2ml/kg by the same way of group A. Aftermanufacturing the model of acute lung injury successfully, the animals were absorbedpure oxygen5min to drive the nitrogen,and then replaced by50%air-oxygen mixturegas to mechanical ventilation;Treatment group(group C): the rabbits were injectedPH=1HCL2ml/kg by the same way of group A.After manufacturing the model ofacute lung injury successfully, the animals were absorbed pure oxygen5min to drivenitrogen, and then replaced by50%helium-oxygen to mechanical ventilation. At thetime point of before injecting HCL0.5h (T0)、 after injecting HCL0.5h(T1) andmechanical ventilation1h (T2)、2h (T3)、3h (T4)、4h(T5), the HR、MAP、VTandPpeak were recorded.Carotid artery blood was extracted to detect the levels of SP-A、SP-B、IL-8by ELISA and PaO2、PaCO2by blood-gas analysis at the same six timepoint. The animals were killed quickly at the time point of T5.The lower lobe of leftlung was used to measure the contents of SP-A、SP-B、IL-8by ELISA and observe thechanges of the lung tissues by optical microscope.The lower lobe of right lung wasweighted the content of water by W/D.Results: There was no obvious difference at each time point in HR and MAP betweenthree groups.Compared with group A,the serum levels of SP-A、SP-B and IL-8wereincreased at other time point except T0in group B and group C,the difference havingstatistical significance (P<0.01);the Ppeak was increased and Cdyn was decreased at other time point except T0in group B,but that change was only occurred at T1ingroup C,the difference having statistical significance (P<0.01);the PaO2was increasedand PaCO2was increased at other time point except T0, the difference having obviousstatistical significance (P<0.01);the lung tissue contents of SP-A and SP-B weredecreased,but the content of IL-8was increased,the difference having statisticalsignificance (P<0.01);the content of water was increased in the lung tissue,thedifference having statistical significance(P<0.05).Compared with group B,Ppeak wasdecreased and Cdyn was improved at other time point except T0and T1,the differencehaving statistical significance (P<0.01);PaO2was increased and PaCO2was decreasedat other time point except T0and T1,the difference having statistical significance(P<0.05);the serum levels of SP-A、SP-B and IL-8were decreased at T5in group C,thedifference having statistical significance (P<0.01);the contents of SP-A and SP-B inthe lung tissue were increased,but the content of IL-8was decreased,the differencehaving statistical significance(P<0.01); the content of water was decreased in the lungtissue,the difference having statistical significance(P<0.05).The serum level of IL-8with SP-A and SP-B showed significant positive correlation respectively in group Band group C (r1B=0.989，r2B=0.995；r1C=0.977，r2C=0.998，P<0.01).Histopathologicalchanges of lung at T5:the microscopic structure of lung tissue was clear and it had nosignificant pathological changes in group A. The pathological changes of lung tissuein group C,concluding edema、hemorrhage、alveolar collapse、protein exudation、inflammatory cell infiltration were lighter than in group B.Conclusions:50%Heliox mechanical ventilation4hours on rabbits with HCL-induce-d acute lung injury under general anesthesia,Ppeak was decreased and Cdyn wasimproved;PaO2was increased and PaCO2was decreased; the serum levels of SP-A、SP-B and IL-8were decreased significantly;the contents of SP-A and SP-B wereincreased,but the contents of IL-8was decreased;the content of water was decreasedand pathological structures was improved significantly in lung tissue.The50%Helioxmechanical ventilation can improve HCL-induced acute lung injury in rabbits,whichmechanism may be related to Heliox reducing airway resistance and increasing lung compliance, promoting oxygenation and carbon dioxide emission, reducing the serumlevels of SP-A、SP-B and IL-8, controlling the immunity and inflammatory reaction,promoting PS synthesis and improving the function of PS systems.