Nijland R, Jongsma H W, Nijhuis J G, Oeseburg B, Zijlstra W G
Department of Obstetrics & Gynaecology, Faculty of Medical Sciences, University of Nijmegen, The Netherlands.
Acta Anaesthesiol Scand Suppl. 1995;107:49-52. doi: 10.1111/j.1399-6576.1995.tb04330.x.
Multi-wavelength photometers, blood gas analysers and pulse oximeters are widely used to measure various oxygen-related quantities. The definitions of these quantities are not always correct. This paper gives insight in the various definitions for oxygen quantities. Furthermore, the possible influences of dyshaemoglobins and fetal haemoglobin on the accuracy of pulse oximetry are discussed. As pulse oximeters are constructed for the determination of arterial oxygen saturation, they should be validated with sample oxygen saturation values and not with the oxyhaemoglobin fraction. The influence of carboxyhaemoglobin is insubstantial over an oxygen saturation range of 0% to 100%. Through the presence of methaemoglobin, pulse oximetry will give an underestimation above 70% and an overestimation below 70% oxygen saturation. The influence of fetal haemoglobin is insignificant in the neonatal use of pulse oximetry, in the range of 75% to 100% arterial oxygen saturation. However, a pulse oximeter underestimates the arterial oxygen saturation at the 25% level with 5%, if the pulse oximeter has been calibrated in human adults. Such a low level of arterial oxygen saturation can be present in the fetus during labor.
多波长光度计、血气分析仪和脉搏血氧仪被广泛用于测量各种与氧相关的量。这些量的定义并不总是正确的。本文深入探讨了氧含量的各种定义。此外，还讨论了异常血红蛋白和胎儿血红蛋白对脉搏血氧测定准确性的可能影响。由于脉搏血氧仪是用于测定动脉血氧饱和度的，因此应该用样本血氧饱和度值而不是氧合血红蛋白分数进行验证。在0%至100%的血氧饱和度范围内，碳氧血红蛋白的影响不大。由于高铁血红蛋白的存在，脉搏血氧测定在血氧饱和度高于70%时会低估，而在低于70%时会高估。在新生儿使用脉搏血氧测定时，在75%至100%的动脉血氧饱和度范围内，胎儿血红蛋白的影响不显著。然而，如果脉搏血氧仪是在成人中校准的，那么在25%的水平下，脉搏血氧仪会低估动脉血氧饱和度5%。在分娩过程中，胎儿体内可能会出现如此低水平的动脉血氧饱和度。
