呼气末二氧化碳在心肺复苏中的应用(综述)

Application of End-Tidal Carbon Dioxide in Cardiopulmonary Resuscitation (Review)

摘要: 人体呼吸分为外呼吸、气体运输、内呼吸三部分，外呼吸包括肺通气、肺换气，肺通气指肺从外界吸入O₂，呼出CO₂，肺换气为肺内部毛细血管与肺泡之间气体交换。内呼吸指机体细胞在代谢时与周围组织、毛细血管进行气体交换，气体运输指细胞代谢所需O₂、产生CO₂随血液流动方向，由毛细血管、静脉、动脉进入肺，通过肺换气、肺通气完成气体交换，气体运输是连接内外呼吸的重要环节。在急危重症中，心跳骤停发生时，机体自主肺通气微弱甚至停止，心脏无法维持正常泵血功能，血流动力学改变导致气体运输环节中止，内呼吸缺少血氧供给，CO₂等代谢产物潴留，细胞代谢无法正常运行，细胞功能受损，此时心肺复苏(CPR, Cardiopulmonary Resuscitation)是抢救患者唯一措施，人工辅助通气替代自主肺通气，胸外按压替代心脏泵血功能，建立人工循环，重启气体运输环节，气体交换恢复，组织细胞代谢产生CO₂随血流运行至肺毛细血管，经肺泡与O₂交换，呼气时排出体外。体内二氧化碳产量、肺通气量、肺血流量是决定肺泡内二氧化碳分压(PetCO₂)主要因素，院内复苏时多为气管插管呼吸机辅助通气，若设置肺通气量恒定，则复苏时血流速度、肺血流量决定PetCO₂。CPR时，血液由上下腔静脉流入右心房，经肺动脉、肺静脉流入左心房，在舒张期，冠状动脉扩张、压力下降，冠脉血流量增加，冠状动脉的有效灌注压是心脏复跳的决定因素，但复苏时往往时间紧促，动静脉有创置管监测血流动力学操作难度较大，故监测PetCO2可间接反应肺血流量、冠状动脉灌注压，是一种无创、方便、快速评估CPR质量的有效手段。

Abstract: Human respiration is divided into three parts: external respiration, gas transport, and internalres-piration. External respiration includes pulmonary ventilation and pulmonary ventilation. Pulmo-nary ventilation refers to inhaling O₂ and exhaling CO₂ from the outside. Pulmonary ventilation is gas exchange between blood capillary and alveoli in the lung. Internal respiration refers to the me-tabolism of cells in the body and the surrounding tissue, The blood capillary carries on the gas ex-change, the gas transportation refers to the cell metabolism needs the O₂, produces the CO₂ along with the blood flow direction, enters the lung by the blood capillary, the vein, the artery, through the lung ventilates completes the gas exchange, the gas transportation is the connection inside and outside the breath important link. In critical illness, cardiac arrest occurs when the body’s own lung ventilation is weak or even stopped, and the heart cannot maintain normal pumping function. He-modynamic changes lead to the suspension of gas transportation, lackof oxygen supply in internal respiration, retention of CO₂ and other metabolites, cell metabolism can not run normally, and cell function is impaired. At this time, cardiopulmonary resuscitation (CPR) is the only measure to res-cue patients. Artificial auxiliary ventilation instead of spontaneous pulmonary ventilation, chest compression instead of blood pumping function of the heart, the establishment of artificial circula-tion, restart the gas transport link, gas exchange recovery, tissue metabolism of CO₂ run along with the blood flow to the pulmonary capillary, through the alveoli and O₂ exchange, exhaled from the body. Intraalveolar partial pressure of carbon dioxide (PetCO₂) is determined by carbon dioxide production in vivo, pulmonary ventilation volume and pulmonary blood flow. In hospital resuscita-tion, most patients were ventilated by intubation and ventilator. If the pulmonary ventilation vol-ume was constant, the blood flow velocity and pulmonary blood flow determined PetCO₂ during re-suscitation. During CPR, the blood flows from the superior and inferior vena cava to the right atri-um, and then to the left atrium through the pulmonary artery and pulmonary vein. In diastole, the coronary artery dilates, the pressure drops, the coronary blood flow increases, the coronary artery effective perfusion pressure is the determinant of heart beat, but the time of resuscitation is often tight, and it is difficult to monitor hemodynamics with invasive catheterization in artery and vein. Therefore, PetCO₂ monitoring can indirectly reflect the pulmonary blood flow, coronary artery per-fusion pressure, is a non-invasive, convenient and rapid assessment of the quality of CPR effective means.