Department of Anesthesiology, Perioperative and Pain Medicine, Division of Critical Care Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
Crit Care Med. 2013 May;41(5):1296-304. doi: 10.1097/CCM.0b013e3182771516.
To utilize real-time electrical impedance tomography to guide lung protective ventilation in an animal model of acute respiratory distress syndrome.
Prospective animal study.
Animal research center.
Twelve Yorkshire swine (15 kg).
Lung injury was induced with saline lavage and augmented using large tidal volumes. The control group (n = 6) was ventilated using ARDSnet guidelines, and the electrical impedance tomography-guided group (n = 6) was ventilated using guidance with real-time electrical impedance tomography lung imaging. Regional electrical impedance tomography-derived compliance was used to maximize the recruitment of dependent lung and minimize overdistension of nondependent lung areas. Tidal volume was 6 mL/kg in both groups. Computed tomography was performed in a subset of animals to define the anatomic correlates of electrical impedance tomography imaging (n = 5). Interleukin-8 was quantified in serum and bronchoalveolar lavage samples. Sections of dependent and nondependent regions of the lung were fixed in formalin for histopathologic analysis.
Positive end-expiratory pressure levels were higher in the electrical impedance tomography-guided group (14.3 cm H₂O vs. 8.6 cm H₂O; p < 0.0001), whereas plateau pressures did not differ. Global respiratory system compliance was improved in the electrical impedance tomography-guided group (6.9 mL/cm H₂O vs. 4.7 mL/cm H₂O; p = 0.013). Regional electrical impedance tomography-derived compliance of the most dependent lung region was increased in the electrical impedance tomography group (1.78 mL/cm H₂O vs. 0.99 mL/cm H₂O; p = 0.001). Pao₂/FIO₂ ratio was higher and oxygenation index was lower in the electrical impedance tomography-guided group (Pao₂/FIO₂: 388 mm Hg vs. 113 mm Hg, p < 0.0001; oxygentation index, 6.4 vs. 15.7; p = 0.02) (all averages over the 6-hr time course). The presence of hyaline membranes (HM) and airway fibrin (AF) was significantly reduced in the electrical impedance tomography-guided group (HMEIT 42% samples vs. HMCONTROL 67% samples, p < 0.01; AFEIT 75% samples vs. AFCONTROL 100% samples, p < 0.01). Interleukin-8 level (bronchoalveolar lavage) did not differ between the groups. The upper and lower 95% limits of agreement between electrical impedance tomography and computed tomography were ± 16%.
Electrical impedance tomography-guided ventilation resulted in improved respiratory mechanics, improved gas exchange, and reduced histologic evidence of ventilator-induced lung injury in an animal model. This is the first prospective use of electrical impedance tomography-derived variables to improve outcomes in the setting of acute lung injury.
利用实时电阻抗断层成像技术指导急性呼吸窘迫综合征动物模型的肺保护性通气。
前瞻性动物研究。
动物研究中心。
12 头约克夏猪（15 公斤）。
盐水灌洗诱导肺损伤，并使用大潮气量增加。对照组（n = 6）根据急性呼吸窘迫综合征网络指南进行通气，电阻抗断层成像引导组（n = 6）使用实时电阻抗断层成像肺成像引导进行通气。使用区域电阻抗断层成像衍生的顺应性来最大限度地募集依赖性肺，最小化非依赖性肺区域的过度膨胀。两组潮气量均为 6 mL/kg。对一部分动物进行计算机断层扫描，以确定电阻抗断层成像的解剖学相关性（n = 5）。在血清和支气管肺泡灌洗液样本中定量白细胞介素-8。将依赖和非依赖肺区的部分固定在福尔马林中进行组织病理学分析。
电阻抗断层成像引导组的呼气末正压水平较高（14.3 cm H₂O 与 8.6 cm H₂O；p < 0.0001），而平台压没有差异。电阻抗断层成像引导组的整体呼吸系统顺应性得到改善（6.9 mL/cm H₂O 与 4.7 mL/cm H₂O；p = 0.013）。电阻抗断层成像组最依赖的肺区的区域电阻抗断层成像衍生顺应性增加（1.78 mL/cm H₂O 与 0.99 mL/cm H₂O；p = 0.001）。电阻抗断层成像引导组的 PaO₂/FIO₂ 比值较高，氧合指数较低（PaO₂/FIO₂：388 mmHg 与 113 mmHg，p < 0.0001；氧合指数，6.4 与 15.7；p = 0.02）（所有平均值在 6 小时时间过程中）。电阻抗断层成像引导组透明膜（HM）和气道纤维蛋白（AF）的存在明显减少（HMEIT 42%样本与 HMCONTROL 67%样本相比，p < 0.01；AFEIT 75%样本与 AFCONTROL 100%样本相比，p < 0.01）。两组间支气管肺泡灌洗液白细胞介素-8 水平无差异。电阻抗断层成像与计算机断层扫描的上下 95%一致性界限为± 16%。
电阻抗断层成像引导通气可改善呼吸力学，改善气体交换，并减少急性肺损伤动物模型中呼吸机诱导性肺损伤的组织学证据。这是首次前瞻性使用电阻抗断层成像衍生变量改善急性肺损伤患者的预后。
