Lurie K G, Mulligan K A, McKnite S, Detloff B, Lindstrom P, Lindner K H
Cardiac Arrhythmia Center, Cardiovascular Division, University of Minnesota, Minneapolis, USA.
Chest. 1998 Apr;113(4):1084-90. doi: 10.1378/chest.113.4.1084.
This study was designed to assess whether intermittent impedance of inspiratory gas exchange improves the efficiency of standard cardiopulmonary resuscitation (CPR).
Standard CPR relies on the natural elastic recoil of the chest to transiently decrease intrathoracic pressures and thereby promote venous blood return to the heart. To further enhance the negative intrathoracic pressures during the "relaxation" phase of CPR, we tested the hypothesis that intermittent impedance to inspiratory gases during standard CPR increases coronary perfusion pressures and vital organ perfusion.
CPR was performed with a pneumatically driven automated device in a porcine model of ventricular fibrillation. Eight pigs were randomized to initially receive standard CPR alone, while seven pigs initially received standard CPR plus intermittent impedance to inspiratory gas exchange with a threshold valve set to -40 cm H2O. The compression:ventilation ratio was 5:1 and the compression rate was 80/min. At 7-min intervals the impedance threshold valve (ITV) was either added or removed from the ventilation circuit such that during the 28 min of CPR, each animal received two 7-min periods of CPR with the ITV and two 7-min periods without the valve.
Vital organ blood flow was significantly higher during CPR performed with the ITV than during CPR performed without the valve. Total left ventricular blood flow (mean+/-SEM) (mL/min/g) was 0.32+/-0.04 vs 0.23+/-0.03 without the ITV (p<0.05). Cerebral blood flow (mL/min/g) was 20% higher with the ITV (+ITV, 0.23+/-0.02; -ITV, 0.19+/-0.02; p<0.05). Each time the ITV was removed, there was a statistically significant decrease in the vital organ blood flow and coronary perfusion pressure.
Intermittent impedance to inspiratory flow of respiratory gases during standard CPR significantly improves CPR efficiency during ventricular fibrillation. These studies underscore the importance of lowering intrathoracic pressures during the relaxation phase of CPR.
本研究旨在评估吸气气体交换的间歇性阻抗是否能提高标准心肺复苏（CPR）的效率。
标准心肺复苏依靠胸部的自然弹性回缩来短暂降低胸腔内压力，从而促进静脉血回流至心脏。为了在心肺复苏的“放松”阶段进一步增强胸腔内负压，我们测试了这样一个假设，即在标准心肺复苏期间对吸气气体进行间歇性阻抗可增加冠状动脉灌注压和重要器官灌注。
在猪心室颤动模型中使用气动自动装置进行心肺复苏。8头猪被随机分配，最初仅接受标准心肺复苏，而7头猪最初接受标准心肺复苏加吸气气体交换的间歇性阻抗，阈值阀设置为-40 cm H₂O。按压与通气比例为5:1，按压速率为80次/分钟。每隔7分钟在通气回路中添加或移除阻抗阈值阀（ITV），使得在28分钟的心肺复苏过程中，每只动物接受两个7分钟有ITV的心肺复苏期和两个7分钟无阀的心肺复苏期。
使用ITV进行心肺复苏时，重要器官血流显著高于不使用阀进行心肺复苏时。左心室总血流（平均值±标准误）（mL/min/g）在使用ITV时为0.32±0.04，不使用ITV时为0.23±0.03（p<0.05）。使用ITV时脑血流（mL/min/g）高20%（+ITV，0.23±0.02；-ITV，0.19±0.02；p<0.05）。每次移除ITV时，重要器官血流和冠状动脉灌注压均有统计学意义的下降。
标准心肺复苏期间对呼吸气体吸气流量进行间歇性阻抗可显著提高心室颤动时的心肺复苏效率。这些研究强调了在心肺复苏放松阶段降低胸腔内压力的重要性。
