Isserles S A, Breen P H
Department of Anesthesia and Critical Care, University of Chicago, IL 60637.
Anesth Analg. 1991 Dec;73(6):808-14. doi: 10.1213/00000539-199112000-00023.
In recent studies of cardiopulmonary resuscitation, an increase in end-tidal carbon dioxide tension (PETCO2) signifies an increase in cardiac output (QT) as spontaneous circulation resumes. We hypothesized that changes in QT might generally be measured by changes in PETCO2. In five pentobarbital-anesthetized dogs, we inflated percutaneously inserted vena cava balloons to impede venous return and to decrease QT (measured by pulmonary thermodulation). The PECTCO2 was measured at the airway opening by sidestream infrared capnometry. In 32 vena cava balloon inflation sequences during constant ventilation in five dogs, the percent decrease in PETCO2 directly correlated with the percent decrease in QT (slope = 0.73, R2 = 0.89, P less than 0.001). During decreased QT, reduced CO2 delivery to the lungs decreased alveolar PCO2 to cause part of the decrease in PETCO2. The remaining reduction in PETCO2 resulted from the increase in alveolar dead space (in turn due to lower pulmonary perfusion pressures during reduced QT), which diluted the CO2 from perfused alveolar spaces to further reduce PETCO2. During a sustained reduction in QT, increasing CO2 accumulation in the peripheral tissues and in venous blood began to restore CO2 delivery to the lung and PETCO2 toward baseline levels. Reciprocal changes occurred during increases in QT when the vena cava balloons were deflated. The linear relationship between changes in PETCO2 and QT in animals supports a decision to perform clinical studies necessary to determine whether a change in PETCO2 will be useful as a noninvasive, continuous monitor of a change in QT during anesthesia or intensive care.
在最近关于心肺复苏的研究中，呼气末二氧化碳分压（PETCO2）的升高表明随着自主循环恢复心输出量（QT）增加。我们假设QT的变化通常可以通过PETCO2的变化来测量。在五只戊巴比妥麻醉的狗中，我们经皮插入腔静脉球囊进行充气以阻碍静脉回流并降低QT（通过肺温度调节测量）。通过旁流红外二氧化碳分析仪在气道开口处测量PETCO2。在五只狗持续通气期间的32次腔静脉球囊充气序列中，PETCO2的降低百分比与QT的降低百分比直接相关（斜率 = 0.73，R2 = 0.89，P小于0.001）。在QT降低期间，输送到肺部的二氧化碳减少导致肺泡PCO2降低，从而引起PETCO2部分降低。PETCO2的其余降低是由于肺泡死腔增加（这又是由于QT降低时肺灌注压力降低所致），这稀释了来自灌注肺泡空间的二氧化碳，进一步降低了PETCO2。在QT持续降低期间，外周组织和静脉血中二氧化碳的积累增加，开始使输送到肺部的二氧化碳和PETCO2恢复到基线水平。当腔静脉球囊放气QT增加时，会出现相反的变化。动物中PETCO2和QT变化之间的线性关系支持进行临床研究的决定，以确定PETCO2的变化是否可用作麻醉或重症监护期间QT变化的无创连续监测指标。
