Influence Of Mechanical Ventilation With Different Tidal Volume On Th1/Th2Balance In Rats With Lipopoiysaccharide Induced Acute Lung Injury

Objective: To investigate Thl/Th2balance in rats with lipopolysaccharide inducedacute lung injury, and to approach the influence of mechanical ventilation with smalltidal volume and traditional tidal volume on Th1/Th2balance in rats withlipopolysaccharide induced acute lung injury and the possible mechanisms.Methods:32male healthy adult SD rats[weight(275±25)g]were random divided intofour groups(n=8): normal sodium contrast group(A), lipopolysaccharide induced acutelung injury with non-mechanical ventilation group(B), lipopolysaccharide induced acutelung injury with small tidal volume(6~8ml/kg) ventilation group(C) andlipopolysaccharide induced acute lung injury with traditional tidal volume(12~15ml/kg)ventilation group(D). B, C, D groups were injected slowly with LPS from the rightexternal jugular vein to induce acute lung injury, and A group with the same volume ofnormal sodium(NS). then monitored the mean arterial pressure, heart rate, and arterialblood gases, calculated their oxygenation index. All rats were observed for3hours afterLPS/NS injection. At the end of the experiment, got5ml peripheral blood from rightventricular puncture to measure IFN-γ, IL-4concentration of PBMC by ELISA andcalculated the ratio of IFN-γ/IL-4. The right lung median lobe was obtained to calculateW/D, and pathological examination of lung tissues that was from the right lung inferiorlobe stained by HE was made under microscope, the white blood cell andpolymorphonuclear neutrophils were measured by autokinetic movement blood cellanalysator in the BALF.Results:1. In addition to A group, MAP of B, C and D group declined overall, whichappeared to be the performance of endotoxic shock; of B, C, D group, theperformances indicators such as oxygenation index (OI), W/D and pathologicalchanges were in line with acute lung injury.2. Compared with A group, IFN-γ, IL-4concentration and IFN-γ/IL-4of B groupmarkedly increased respectively, the difference was significant (P<0.05). Comparedwith B group, IFN-γ concentration, IFN-γ/IL-4of C group were markedly lowerrespectively, the difference was significant (P<0.05). Compared with B group, IFN-γ concentration, IFN-γ/IL-4of D group were markedly increased respectively, thedifference was significant (P<0.05).3. Compared with A group, the lung W/D and the WBC, PMN in BALF of B groupincreased markedly respectively, the difference was statistically significant (P<0.05).Compared with B group, the ratio of lung W/D and the WBC, PMN in BALF of Cgroup were markedly decreased respectively, the difference was statistically significant(P<0.05). Compared with B group, the ratio of W/D and the WBC, PMN in BALF ofD group was markedly increased respectively, the difference was statisticallysignificant (P<0.05).Conclusions:1. Injection of lipopolysaccharide in rats from external jugular vein cansuccessfully reproduced animal models of ALI.2. IFN-γ and IL-4concentration in PBMC, IFN-γ/IL-4ratio increased in the ratsinduced with lipopolysaccharide early, so Thl/Th2imbalances, and excursion to Th1occurs.3. Mechanical ventilation with traditional tidal volume can exacerbate lung injury in therats induced with lipopolysaccharide during inflammatory response, so that aggravateTh1/Th2imbalances of the early lung injury in rats.4. Mechanical ventilation with small tidal volume as a protective ventilation strategy ofendotoxin lung injury in rats can lighten the PMN keep in the lung, may reduce theinflammatory response and correct the Th1/Th2imbalance.