Abstract：
Rationale: It is unknown whether preventing overdistention or collapse is more important when titrating positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS). Objectives: To compare PEEP targeting minimal overdistention or minimal collapse or using a compromise between collapse and overdistention in a randomized trial and to assess the impact on respiratory mechanics, gas exchange, inflammation, and hemodynamics. Methods: In a porcine model of ARDS, lung collapse and overdistention were estimated using electrical impedance tomography during a decremental PEEP titration. Pigs were randomized to three groups and ventilated for 12 hours: PEEP set at ⩽3% of overdistention (low overdistention), ⩽3% of collapse (low collapse), and the crossing point of collapse and overdistention. Measurements and Main Results: Thirty-six pigs (12 per group) were included. Median (interquartile range) values of PEEP were 7 (6-8), 11 (10-11), and 15 (12-16) cm H2O in the three groups (P < 0.001). With low overdistension, 6 (50%) pigs died, whereas survival was 100% in both other groups. Cause of death was hemodynamic in nature, with high transpulmonary vascular gradient and high epinephrine requirements. Compared with the other groups, pigs surviving with low overdistension had worse respiratory mechanics and gas exchange during the entire protocol. Minimal differences existed between crossing-point and low-collapse animals in physiological parameters, but postmortem alveolar density was more homogeneous in the crossing-point group. Inflammatory markers were not significantly different. Conclusions: PEEP to minimize overdistention resulted in high mortality in an animal model of ARDS. Minimizing collapse or choosing a compromise between collapse and overdistention may result in less lung injury, with potential benefits of the compromise approach.
摘要：
背景：在急性呼吸窘迫综合征（ARDS）中滴定呼气末正压（PEEP）时，预防过度膨胀或塌陷是否更重要尚不清楚。
目的：为了比较PEEP靶向最小过度扩张，在随机试验中，最小塌陷或使用塌陷和过度膨胀之间的折衷，并评估对呼吸力学的影响，气体交换,炎症,和血液动力学。
方法：在猪ARDS模型中，在递减的PEEP滴定过程中,通过电阻抗断层扫描评估肺塌陷和过度扩张.将猪随机分为三组并通气12小时:PEEP设定为≤3%的过度膨胀(低过度膨胀);≤3%的塌陷(低塌陷);以及塌陷和过度膨胀的交叉点(交叉点)。
结果:包括36头猪(12只/组)。平均PEEP为7(IQR:6-8)cmH2O，11(10-11)cmH2O,三组中有15(12-16)cmH2O，p<0.001。低扩张，6只（50％）猪死亡，而其他两组的存活率均为100％。死因本质上是血液动力学，具有高的经肺梯度和高的肾上腺素需求。与其他组相比，在整个方案中，低膨胀存活的猪的呼吸力学和气体交换较差。交叉点和低塌陷动物在生理参数上存在最小差异，但死后肺泡密度在交叉点上更为均匀。炎症标志物没有显著差异。
结论：PEEP使过度扩张最小化，导致ARDS动物模型的高死亡率。尽量减少塌陷或在塌陷和过度扩张之间选择折衷可能会减少肺损伤。具有折衷方法的潜在好处。
目的：为了比较PEEP靶向最小过度扩张，在随机试验中，最小塌陷或使用塌陷和过度膨胀之间的折衷，并评估对呼吸力学的影响，气体交换,炎症,和血液动力学。
方法：在猪ARDS模型中，在递减的PEEP滴定过程中,通过电阻抗断层扫描评估肺塌陷和过度扩张.将猪随机分为三组并通气12小时:PEEP设定为≤3%的过度膨胀(低过度膨胀);≤3%的塌陷(低塌陷);以及塌陷和过度膨胀的交叉点(交叉点)。
结果:包括36头猪(12只/组)。平均PEEP为7(IQR:6-8)cmH2O，11(10-11)cmH2O,三组中有15(12-16)cmH2O，p<0.001。低扩张，6只（50％）猪死亡，而其他两组的存活率均为100％。死因本质上是血液动力学，具有高的经肺梯度和高的肾上腺素需求。与其他组相比，在整个方案中，低膨胀存活的猪的呼吸力学和气体交换较差。交叉点和低塌陷动物在生理参数上存在最小差异，但死后肺泡密度在交叉点上更为均匀。炎症标志物没有显著差异。
结论：PEEP使过度扩张最小化，导致ARDS动物模型的高死亡率。尽量减少塌陷或在塌陷和过度扩张之间选择折衷可能会减少肺损伤。具有折衷方法的潜在好处。
