Otto Cynthia M, Markstaller Klaus, Kajikawa Osamu, Karmrodt Jens, Syring Rebecca S, Pfeiffer Birgit, Good Virginia P, Frevert Charles W, Baumgardner James E
Departmrnt of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, PA, USA.
J Appl Physiol (1985). 2008 May;104(5):1485-94. doi: 10.1152/japplphysiol.01089.2007. Epub 2008 Mar 6.
Volutrauma and atelectrauma have been proposed as mechanisms of ventilator-associated lung injury, but few studies have compared their relative importance in mediating lung injury. The objective of our study was to compare the injury produced by stretch (volutrauma) vs. cyclical recruitment (atelectrauma) after surfactant depletion. In saline-lavaged rabbits, we used high tidal volume, low respiratory rate, and low positive end-expiratory pressure to produce stretch injury in nondependent lung regions and cyclical recruitment in dependent lung regions. Tidal changes in shunt fraction were assessed by measuring arterial Po(2) oscillations. After ventilating for times ranging from 0 to 6 h, lungs were excised, sectioned gravitationally, and assessed for regional injury by evaluation of edema formation, chemokine expression, upregulation of inflammatory enzyme activity, and alveolar neutrophil accumulation. Edema formation, lung tissue interleukin-8 expression, and alveolar neutrophil accumulation progressed more rapidly in dependent lung regions, whereas macrophage chemotactic protein-1 expression progressed more rapidly in nondependent lung regions. Temporal and regional heterogeneity of lung injury were substantial. In this surfactant depletion model of acute lung injury, cyclical recruitment produced more injury than stretch.
容积伤和肺不张伤已被提出作为呼吸机相关性肺损伤的机制，但很少有研究比较它们在介导肺损伤中的相对重要性。我们研究的目的是比较表面活性剂耗竭后拉伸（容积伤）与周期性复张（肺不张伤）所产生的损伤。在盐水灌洗的兔中，我们使用高潮气量、低呼吸频率和低呼气末正压在非下垂肺区域产生拉伸损伤，并在下垂肺区域产生周期性复张。通过测量动脉血氧分压振荡来评估分流分数的潮式变化。通气0至6小时后，切除肺脏，重力切片，并通过评估水肿形成、趋化因子表达、炎性酶活性上调和肺泡中性粒细胞积聚来评估局部损伤。水肿形成、肺组织白细胞介素-8表达和肺泡中性粒细胞积聚在下垂肺区域进展更快，而巨噬细胞趋化蛋白-1表达在非下垂肺区域进展更快。肺损伤的时间和局部异质性很大。在这个急性肺损伤的表面活性剂耗竭模型中，周期性复张比拉伸产生的损伤更大。
