The Effect Of Different Tidal Volumes Mechanical Ventilation On Lung Injury In Dogs During Cardiopulmonary Resuscitation

Objective: To observe the changes of lung injury with different tidal volumes (TV)mechanical ventilation during cardiopulmonary resuscitation. Discuss the mechanismof lung injury after cardiopulmonary resuscitation and mechanical ventilationstrategy.Method: A total of24healthy, adult and mongrel canines were randomly dividedinto control group (group A:no ventricular fibrillation and mechanical ventilation) andexperiment group (group B:Ventricular fibrillation was induced with pacing catheterput through right external carotid vein into the right ventricle, CPR was initiated withdifferent TV mechanical ventilation after3min of ventricular fibrillation). Theexperiment group were divided into B₁and B₂two subgroups based on the TV. B₁:TV6ml/Kg body weight; B₂: TV20ml/Kg body weight. Ventilation in both subgroupswas maintained for6hours. The indexes of arterial blood gas was tested in differenttimes. Comparing the rate of successful return of spontaneous circulation(ROSC) andthe72h survival rate. The consistency of TLR4and phosphatidylchline in bronchiaalveolus lavage fluid (BALF) was tested in cellular ELISA and HPLC. The ratio ofwet and dry weight and the morphological change scores of lung tissue werecalculated.Results:(1) The rate of successful return of spontaneous circulation(ROSC) andthe72h survival rate were: B₁:75%,50%; B₂:62.5%,40%. They were no statisticallysignificant (p＞0.05).(2) After ventricular fibrillation, pH, PaO₂, in both subgroupswere decreased, PaCO₂was raised (p＜0.05). After ROSC pH, PaO₂, in bothsubgroups were elevated, the decline of PaCO₂in group B₂has statistical significancewith B₁in2hours after ROSC. The different of HCO3-between B₁and B₂hasstatistical significance in6hours after ROSC (p＜0.05).(3) The protein of TLR4inBALF in group B were greatly increased as compared with the group A(All P＜0.01),while group B₂increased much more than B₁(P＜0.05). The consistency ofphosphatidylchline in group B were greatly decreased as compared with the group A while while group B2decreased much more than B1(P＜0.05).(4) The W/D ratioand morphological change scores in group B were higher than A, while In B2theywere higher than B1(P＜0.05).(5) Correlation analysis demonstrated that themorphological change score of lung tissue was positively correlated with the contentof TLR4(r=0.770, P＜0.01),negatively correlated with the content ofphosphatidylchline (r=-0.750,P＜0.01).Conclusions Mechanical ventilation can be effective in improving hypoxemia aftercardiac arrest. Low tidal volume ventilation can reduce the TLR4content anddecrease the loss of pulmonary surfactant to mitigate pulmonary injury afterresuscitation.