低潮气量通气改善猪急性肺损伤模型的脑组织氧合

背景本研究探讨在猪急性肺损伤（ALI）模型中应用不同潮气量对脑组织氧合和代谢的影响。我们假设在实验诱导急性肺损伤后，低潮气量（LT）机械通气能改善其脑组织的氧合和代谢。方法通过去除肺表面活性物质诱导实验性的急性肺损伤模型，10只母猪分别置于两种通气环境下：①6ml／kg的LT容量通气（LT组）；②12ml／kg的高潮气量机械通气（HT组）。分析气体交换、血流动力学、持续脑组织氧张力（ptiO2）、大脑微量透析和全身细胞因子等变量。诱导Au后，收集2、4和8小时的数值。主要观察指标为ptiO2的改变。组间比较采用t检验。P〈0．05为差异有显著性。结果基础状态和Au诱导后，未发现ptiO2存在组间差异；但是，HT组ptiO2在Au的4和8小时后显著降低。PaO2和PaCO2在任何记录时间点均无明显差异。大脑微量透析方面，HT组细胞外乳酸在2、4和8小时显示显著高水平。由于细胞因子的释放导致HT组IL-6和IL-8呈较高水平。结论在猪ALI模型中，与高潮气量通气比较，低潮气量保护性通气可以显著改善脑组织氧合和代谢。动脉氧合和大脑组织氧合存在分离现象。HT组的大脑组织氧合和代谢可能因更为突出的炎性反应而受损。

BACKGROUND： In study, we investigated the effects of different tidal volumes on cerebral tissue oxygenation and cerebral metabolism in a porcine model of acute lung injury （ALI）. We hypothesized that mechanical ventilation with low tidal （LT） volumes improves cerebral tissue oxygenation and metabolism after experimentally induced ALI. METHODS： After inducing experimental ALl by surfactant depletion, we studied two conditions in 10 female pigs： 1 ） LT volume ventilation with 6 ml/kg body weight, and 2） high tidal （HT） volume ventilation with 12 ml/kg body weight. Variables of gas exchange, hemodynamic, continuous cerebral tissue oxygen tension （ptiO2）, cerebral microdialysis, and systemic cytokines were analyzed. After induction of ALI, data were collected at 2, 4, and 8 h. The primary end point was the change in ptiO2. For group comparisons, a t-test was used. A value of 〈 0. 05 was considered to indicate statistical significance. RESULTS： At baseline and after induction of ALI, no differences between groups were found in ptiO2; however, ptiO2 was significantly lower in the HT group after 4 and 8 h. Pat2 and Paco2 showed no significant differences between the groups at all timepoints. Regarding cerebral microdialysis, a significantly higher level of extracellular lactate could be demonstrated after 2,4, and 8 h in the HT group. The release of cytokines resulted in higher values for interleukin-6 and interleukin-8 in the HT group. CONCLUSION： Protective ventilation with LT yielded a significant improvement in cerebral tissue oxygenation and metabolism compared to HT ventilation in a porcine model of ALI. There was dissociation between arterial and cerebral tissue oxygenation. Cerebral oxygenation and metabolism might have possibly been impaired by a more distinctive inflammatory response in the HT group.