理解的对吗？谢谢

In this issue of Anesthesiology, Burnett et al. analyze the accuracy of pulse oximeters in a large retrospective cohort of anesthetized patients with varying degrees of skin pigmentation.3 It was noted in previous studies of volunteer subjects and intensive care unit patients that pulse oximeter readings were erroneously higher at lower saturations in patients with darker skin.4 This current operating room study analyzed 11 yr of data from 46,000 patients under anesthesia. Their surrogate marker for skin pigmentation was self- reported race in the categories of White, Black, Hispanic, Asian, and Other. They estimated arterial oxygen saturation (Sao2) by calculating saturation from blood gas data. The traditional way of assessing the accuracy of two methods of measuring a variable (e.g., oxygen saturation measured by pulse oximetry [Spo2] vs. Sao2) is by a bias analysis—that is, the mean difference between the two measures and the SD of those differences. The bias being the average difference is the systematic error, and the SD of differences (or precision, as it is sometimes called) the random error.

In addition to determining the bias and precision by skin pigmentation groups, they also chose a clinical measure of the incidence of unrecognized hypoxemia defined as a saturation Sao2 less than 88% when the Spo2 reading was greater than 92 to 96%. In this analysis, they found that the incidence of occult hypoxemia differed with skin pigmentation (e.g., White, 1.1%; Hispanic, 1.8%; and Black, 2.1%). The good news is this is a low incidence; the better news is that for the group with Spo2 greater than 96%, incidence was rare, and there were no differences among racial/ethnic groups. So, the clinical bottom line is to keep the Spo2 greater than 96%. If that cannot be achieved by increasing fraction of inspired oxygen or modifying positive end-expiratory pressure, an invasive blood sample may be considered.

在本期《麻醉学》中，Burnett等在不同程度肤色的麻醉患者的大型回顾性队列中，分析了脉氧仪的准确性。以往志愿受试者和重症监护室患者的研究中注意到，肤色较深的患者氧饱和度较低时，脉氧仪读数会正偏倚。本手术室研究分析了11年46000例麻醉患者的数据。其研究中的皮肤色素人群包含白种人、黑种人、西班牙人、亚洲人和其他种族。通过从血气数据计算饱和度来估计动脉血氧饱和度（Sao2）。过去评估两种变量（例如，通过脉氧仪测量的氧饱和度[Spo2]与Sao2）测量准确性的方法是通过偏倚分析——即，两种测量值之间的均数差和这些均数差的SD。均数差的偏倚是系统误差，均数差的SD（或有时称为精确度）是随机误差。

除了通过肤色组患者来确定偏倚和精确度外，他们还选择了一种临床测量未识别低氧血症发生率（定义为Spo2读数大于92~96 %时Sao2小于88 %）的方法来确定偏倚和精确度。在本研究中，他们发现隐匿性低氧血症的发生率因不同肤色而不同（例如：白种人1.1 %、西班牙裔1.8 %、黑2.1 % ）。好消息是，这种未识别的低氧血症发生率低，更好的消息是，当Spo2大于96 %时，这种未识别的低氧血症发生率极低，且种族/民族间没有差异。所以，临床的底线是保持Spo2大于96 %。如果不能通过增加吸入氧浓度或改变呼气末正压来达到这一目的，则可考虑有创血液样本检查。

理解的对吗？