Mahutte C K, Jaffe M B, Sasse S A, Chen P A, Berry R B, Sassoon C S
Department of Medicine, Veterans Affairs Medical Center, Long Beach, California 90822.
Chest. 1993 Oct;104(4):1236-42. doi: 10.1378/chest.104.4.1236.
To determine the individual contributions of variables in the Fick equation to cardiac output, we simultaneously measured oxygen uptake (VO2), carbon dioxide production (VCO2), venous oxygen saturation (SvO2) and thermodilution cardiac output (Qth) in 28 medical and surgical ICU patients. Patients were intubated and ventilated with the intermittent mandatory ventilation mode. VO2 and VCO2 (averaged over 3 min) were obtained from a metabolic cart. SvO2 was measured with fiberoptic reflectance oximetry (and COoximetry). Thirty-nine studies (average duration, 4.3 h) with 151 Qth measurements were performed. The relationships between Qth and VO2, Qth and VCO2, Qth and SvO2, and 1/Qth and SvO2, as well as between the sequential changes in these variables were analyzed by least squares linear regression. The ability of changes in the variables VO2, VCO2, and SvO2 to predict changes in Qth were analyzed by receiver operating characteristic (ROC) curves. Qth was weakly related to VO2 (r = 0.45), VCO2 (r = 0.45), or SvO2 (r = 0.36). Changes in Qth were weakly related to changes in VCO2 (r = 0.40), and even less to changes in VO2 (r = 0.18) and SvO2 (r = 0.13). The areas under the ROC curves for increases in Qth > 10 percent were as follows: 0.66 for VCO2, 0.50 for VO2, and 0.55 for SvO2. The areas for decreases in Qth < 10 percent were as follows: 0.78 for VCO2, 0.65 for VO2, and 0.49 for SvO2. None of the above oximetry relationships were substantially altered by use of COoximetry venous oxygen saturations. We conclude that Qth cannot be predicted well solely from VO2, VCO2, or SvO2 nor can changes in Qth be predicted well solely from changes in VO2, VCO2, or SvO2. Of the metabolic variables, changes in VCO2 best predicted changes in Qth.
为确定菲克方程中各变量对心输出量的个体贡献，我们同时测量了28例内科和外科重症监护病房患者的氧摄取量（VO₂）、二氧化碳产生量（VCO₂）、静脉血氧饱和度（SvO₂）和热稀释法心输出量（Qth）。患者接受气管插管并采用间歇强制通气模式进行通气。VO₂和VCO₂（3分钟平均值）通过代谢监测仪获取。SvO₂采用光纤反射血氧饱和度测定法（和一氧化碳血氧饱和度测定法）进行测量。共进行了39项研究（平均时长4.3小时），包含151次Qth测量。通过最小二乘线性回归分析Qth与VO₂、Qth与VCO₂、Qth与SvO₂以及1/Qth与SvO₂之间的关系，以及这些变量的顺序变化之间的关系。通过受试者工作特征（ROC）曲线分析VO₂、VCO₂和SvO₂变量变化对Qth变化的预测能力。Qth与VO₂（r = 0.45）、VCO₂（r = 0.45）或SvO₂（r = 0.36）的相关性较弱。Qth的变化与VCO₂的变化相关性较弱（r = 0.40），与VO₂（r = 0.18）和SvO₂（r = 0.13）的变化相关性更小。Qth增加> 10%时，ROC曲线下面积如下：VCO₂为0.66，VO₂为0.50，SvO₂为0.55。Qth降低< 10%时，面积如下：VCO₂为0.78，VO₂为0.65，SvO₂为0.49。使用一氧化碳血氧饱和度测定法测得的静脉血氧饱和度并未显著改变上述任何血氧饱和度关系。我们得出结论，仅根据VO₂、VCO₂或SvO₂无法很好地预测Qth，仅根据VO₂、VCO₂或SvO₂的变化也无法很好地预测Qth的变化。在代谢变量中，VCO₂的变化对Qth变化的预测效果最佳。
