向编辑:
We would like to comment on the recently published study by Muñozet al.1, which analysed accuracy and precision of pulse oximetry at different carbon dioxide arterial tension (PA,CO.2) levels. Although the paper investigates an interesting hypothesis, significant limitations should be addressed.
The most important limitation is that the reported meanPA,CO.245.3±8.0 mmHg不完全反映Hypercapnia。截至45.0 mmhg是一个接受的边界值PA,CO.2, the conclusions drawn by Muñozet al.1他们的结果没有充分支持。虽然作者排除了蓝色指甲油,但其他颜色,如深绿色或黑色,可能有更明显的效果2,3.
One significant statement Muñozet al.1make is thatPA,CO.2might directly affect pulse oximetry readings. They emphasise that carbohaemoglobin may be the cause of this measurement bias. The sole effect of carbohaemoglobin was neither analysed nor measured in the study by Muñozet al.1, nor is their hypothesis supported by any other published study. However, hypercapnia has been proven to have an indirect effect due to vasoconstriction and consecutive alterations of perfusion4, giving a more likely explanation for the effects observed.
The calculation of bias by Muñozet al.1was not performed as usual or as suggested by Bland and Altman5: the gold standard should be subtracted from the measured valuee.g.bias equalled arterial O2measured by pulse oximetry (Sp,O2), minus arterial O2saturation (SA,O.2). For data interpretation, the use of a regression line for the cloud of data points does not seem adequate. Removal of one single data point (∼64 mmHg on the x-axis; -13% on the y-axis; see figs 1a or 2c of1),可能导致类似于其他图中的线的水平回归线。
虽然脉搏血氧测定是在临床环境中定期使用的建立技术,但更新和改进的设备需要继续重新评估限制和影响因素。我们全心全意地同意muñozet al.1that arterial blood gas analysis remains the gold standard, supported but not replaced by pulse oximetry readings.
Statement of interest
没有宣布。
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