一种连续无创测量混合静脉血氧饱和度的方法

临床麻醉中混合静脉血氧饱和度监测具有重要的作用，需要通过置入的肺动脉导管进行测量，该方法属于有创方法，具有一定的并发症和风险，同时需要一定的临床操作经验，下面介绍一种无创的连续监测方法，当然了，还处于动物实验验证阶段，期待能用于临床的，无创的，简便的监测方法。

一种连续无创测量混合静脉血氧饱和度的方法：一项对猪的概念验证研究

背景：混合静脉血氧饱和度（SvO2）在评价供氧与全身耗氧平衡时非常重要。到目前为止，监测SvO2需要肺动脉导管采集血样。本文将容积式容量二氧化碳描记术（volumetric capnography，测量有效的肺血流的方法）与Fick氧耗量原理相结合，建立了一种连续无创的capnodynamic SvO2法来测量SvO2。这项研究的目的是通过SvO2测量金标准来验证这项新技术，通过肺动脉导管获取血样是心输出量（CO）-氧饱和度是SvO2测量的（CO-oximetry SvO2）金标准，并评估肺内分流的潜在影响。

方法：8头麻醉机械通气的家养仔猪（平均体重23.9kg）接受一系列旨在降低和增加SvO2的干预措施。在整个研究方案中，同时记录capnodynamic SvO2和CO-oximetry SvO2以及分流分数，使用Berggren公式。采用Bland-Altman图和协方差分析法评估capnodynamic SvO2和CO-oximetry SvO2绝对值的一致性以及capnodynamic SvO2检测变化的能力。

结果：capnodynamic SvO2与CO-oximetry SvO2的总偏差为-1个百分点（一致性限为-13至+11个百分点），平均百分误差为22%，一致性为100%。分流分数在基线时为13%，在研究结束时为22%，并且测试方法之间的一致性只有微小的变化。

结论：在目前的实验环境下，SvO2的capnodynamic法测量值的绝对值非常接近于CO-oximetry法的测量值，并且有100%的趋势分析能力。

A Continuous Noninvasive Method to Assess Mixed Venous Oxygen Saturation: A Proof-of-Concept Study in Pigs

Background: Mixed venous oxygen saturation (SvO2) is important when evaluating the balance between oxygen delivery and whole-body oxygen consumption. Monitoring SvO2 has so far required blood samples from a pulmonary artery catheter. By combining volumetric capnography, for measurement of effective pulmonary blood flow, with the Fick principle for oxygen consumption, we have developed a continuous noninvasive method, capnodynamic SvO2, for assessment of SvO2. The objective of this study was to validate this new technique against the gold standard cardiac output (CO)-oximetry SvO2 measurement of blood samples obtained from a pulmonary artery catheter and to assess the potential influence of intrapulmonary shunting.

Methods: Eight anesthetized mechanically ventilated domestic-breed piglets of both sexes (median weight 23.9 kg) were exposed to a series of interventions intended to reduce as well as increase SvO2. Simultaneous recordings of capnodynamic and CO-oximetry SvO2 as well as shunt fraction, using the Berggren formula, were performed throughout the protocol. Agreement of absolute values for capnodynamic and CO-oximetry SvO2 and the ability for capnodynamic SvO2 to detect change were assessed using Bland-Altman plot and concordance analysis.

Results: Overall bias for capnodynamic versus CO-oximetry SvO2 was -1 percentage point (limits of agreement -13 to +11 percentage points), a mean percentage error of 22%, and a concordance rate of 100%. Shunt fraction varied between 13% at baseline and 22% at the end of the study and was associated with only minor alterations in agreement between the tested methods.

Conclusions: In the current experimental setting, capnodynamic assessment of SvO2 generates absolute values very close to the reference method CO-oximetry and is associated with 100% trending ability.