气道压对心肺复苏效果影响的实验研究

Experimental study on effect of airway pressure on cardiopulmonary resuscitation

目的观察心肺复苏（CPR）时不同气道压对心搏骤停（CA）猪通气和器官灌注以及自主循环恢复（ROSC）的影响，探讨气道正压在CPR时可能的有益机制。方法清洁级健康小型长白猪20只，按随机数字表法分为低气道压组（LP组）和高气道压组（HP组），每组10只。采用电刺激法复制心室纤颤（室颤）动物模型，持续8 min后给予机械胸外心脏按压和机械通气（容量控制模式，潮气量7 mL/kg，通气频率10次/min），LP组呼气末正压（PEEP）设置为0，HP组PEEP设置为6 cmH2O（1 cmH2O=0.098 kPa）；复苏10 min后给予最多3次100 J双向波电除颤。观察动物ROSC情况；记录基础状态、复苏5 min和10 min时的呼吸参数、动静脉血气分析及血流动力学参数。结果HP组ROSC动物明显多于LP组（只：8比3，P〈0.05）。HP组胸外按压放松期胸腔压力均为负值，其绝对值均小于同期LP组〔胸腔负压峰值（cmH2O）：复苏5 min为-4.7±2.2比-10.8±3.5，复苏10 min为-3.9±2.8比-6.5±3.4〕，仅5 min时差异有统计学意义（P〈0.01）；同时HP组复苏期间的胸腔压力变异度也显著大于LP组（cmH2O：复苏5 min为22.5±7.9比14.2±4.4，复苏10 min为23.1±6.4比12.9±5.1，均P〈0.01）。与LP组比较，HP组复苏5 min时的动脉血氧分压〔PaO2（mmHg，1 mmHg=0.133 kPa）：81.5±10.7比68.0±12.1〕和静脉血氧饱和度（SvO2：0.493±0.109比0.394±0.061）以及复苏10 min时的PaO2（mmHg：77.5±13.4比63.3±10.5）、动脉血pH值（7.28±0.09比7.23±0.11）、SvO2（0.458±0.096比0.352±0.078）、主动脉压〔AoP（mmHg）：39.7±9.5比34.0±6.9〕、冠状动脉灌注压〔CPP（mmHg）：25.2±9.6比19.0±7.6〕和颈动脉血流（mL/min：44±16比37±14）均显著升高（均P〈0.05），而复苏10 min时的动脉血二氧化碳分压（PaCO2）则显著降低（mmHg：60.1±9.7比67.8±8.6，P〈0.05）。结论对CA猪CPR时设置一定程度的气道正压较低气道压力可维持胸外按压放松期胸腔负压，同时可增加胸腔压力变异度，改善氧合和血流动力学，并有助于ROSC。

ObjectiveTo observe the effect of different airway pressure on ventilation, organ perfusion and return of spontaneous circulation （ROSC） of cardiac arrest （CA） pigs during cardiopulmonary resuscitation （CPR）, and to explore the possible beneficial mechanism of positive airway pressure during CPR.MethodsTwenty healthy landrace pigs of clean grade were divided into low airway pressure group （LP group, n = 10） and high airway pressure group （HP group, n = 10） with random number table. The model of ventricular fibrillation （VF） was reproduced by electrical stimulation, and mechanical chest compressions and mechanical ventilation （volume-controlled mode, tidal volume 7 mL/kg, frequency 10 times/min） were performed after 8 minutes of untreated VF. Positive end expiratory pressure （PEEP） in LP group and HP group was set to 0 cmH2O and 6 cmH2O （1 cmH2O = 0.098 kPa） respectively. Up to three times of 100 J biphasic defibrillation was delivered after 10 minutes of CPR. The ROSC of animals were observed, and the respiratory parameters, arterial and venous blood gas and hemodynamic parameters were recorded at baseline, 5 minutes and 10 minutes of CPR.ResultsThe number of animals with ROSC in the HP group was significantly more than that in the LP group （8 vs. 3, P 〈 0.05）. Intrathoracic pressure during chest compression relaxation was negative in the HP group, and its absolute value was significantly lower than that in LP group at the same time [intrathoracic negative pressure peak （cmH2O）： -4.7±2.2 vs. -10.8±3.5 at 5 minutes, -3.9±2.8 vs. -6.5±3.4 at 10 minutes], however, there was significantly difference only at 5 minutes of CPR （P 〈 0.01）. Intrathoracic pressure variation during CPR period in the HP group were significantly higher than those in the LP group （cmH2O： 22.5±7.9 vs. 14.2±4.4 at 5 minutes, 23.1±6.4 vs. 12.9±5.1 at 10 minutes, both P 〈 0.01）. Compared to the LP group, arterial partial pressure of oxygen [PaO2 （mmHg, 1 mmHg = 0.133 kPa）： 81.5±10.7 vs. 68.0±12.1], venous oxygen saturation （SvO2： 0.493±0.109 vs. 0.394±0.061） at 5 minutes of CPR, and PaO2 （mmHg： 77.5±13.4 vs. 63.3±10.5）, arterial pH （7.28±0.09 vs 7.23±0.11）, SvO2 （0.458±0.096 vs. 0.352±0.078）, aortic blood pressure [AoP （mmHg）： 39.7±9.5 vs. 34.0±6.9], coronary perfusion pressure [CPP （mmHg）： 25.2±9.6 vs. 19.0±7.6], and carotid artery flow （mL/min： 44±16 vs. 37±14） at 10 minutes of CPR in the HP group were significantly higher （all P 〈 0.05）. Arterial partial pressure of carbon dioxide （PaCO2） in the HP group was significantly lower than that in the LP group at 10 minutes of CPR （mmHg： 60.1±9.7 vs. 67.8±8.6, P 〈 0.05）.ConclusionsCompared to low airway pressure, a certain degree of positive airway pressure can still maintain the negative intrathoracic pressure during relaxation of chest compressions of CPR, while increase the degree of intrathoracic pressure variation. Positive airway pressure can improve oxygenation and hemodynamics during CPR, and is helpful to ROSC.