Keenan Centre for Biomedical Research, Critical Care Department, St. Michael's Hospital, Unity Health Toronto, Toronto, Ontario, Canada.
Interdepartmental Division of Critical Care Medicine and.
Am J Respir Crit Care Med. 2024 Jun 15;209(12):1441-1452. doi: 10.1164/rccm.202310-1895OC.
It is unknown whether preventing overdistention or collapse is more important when titrating positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS). 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. 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. 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 HO in the three groups ( < 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. 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.
在急性呼吸窘迫综合征（ARDS）中，调整呼气末正压（PEEP）时，防止过度膨胀或塌陷哪个更重要尚不清楚。本研究旨在通过随机试验比较最小过度膨胀或最小塌陷目标的 PEEP 与塌陷和过度膨胀之间的妥协策略，并评估其对呼吸力学、气体交换、炎症和血液动力学的影响。在 ARDS 的猪模型中，通过递减 PEEP 滴定过程中的电阻抗断层成像来估计肺塌陷和过度膨胀。将猪随机分为三组并通气 12 小时：PEEP 设置为过度膨胀的 ⩽3%（低过度膨胀）、塌陷的 ⩽3%（低塌陷）和塌陷与过度膨胀的交叉点。纳入 36 头猪（每组 12 头）。三组的 PEEP 中位数（四分位距）分别为 7（6-8）、11（10-11）和 15（12-16）cmH2O（ < 0.001）。在低过度膨胀组中，有 6 头（50%）猪死亡，而其他两组的存活率均为 100%。死亡的原因是血流动力学性质，伴有跨肺血管梯度高和肾上腺素需求高。与其他两组相比，存活的低过度膨胀猪在整个方案期间的呼吸力学和气体交换更差。在生理参数方面，交叉点与低塌陷动物之间存在微小差异，但在交叉点组中，肺泡密度更均匀。炎症标志物无明显差异。在 ARDS 动物模型中，最小化过度膨胀的 PEEP 导致高死亡率。最小化塌陷或在塌陷和过度膨胀之间选择妥协可能会导致较少的肺损伤，而妥协方法可能具有潜在的益处。
