Steinke J M, Shepherd A P
Am J Physiol. 1987 Jul;253(1 Pt 2):H147-53. doi: 10.1152/ajpheart.1987.253.1.H147.
Fiberoptic oximeters measure oxyhemoglobin saturation from the optical reflectance of whole blood, but the calibration of such oximeters is hematocrit dependent. Therefore, using photon-diffusion theory and an empirical approach, we have developed a new reflectance method that determines hematocrit and correspondingly corrects the oxyhemoglobin-saturation measurement. Our method employs four fiber-optic light guides, a photodetector, and three inexpensive light-emitting diodes (one with emissions at 660 nm and two at 813 nm). Hematocrit is determined from the ratio of reflectances from the differently spaced emitting fibers at 813 nm and is used to correct the 813-660 nm measurement of oxyhemoglobin saturation. In red cell suspensions, the mean difference between reflectance measurements of hematocrit and conventional determinations was only 2.09% (r = 0.99), and when compared with conventional gasometric measurements of oxyhemoglobin saturation, the reflectance method yielded the same calibration curve for different hematocrits and gave a mean difference of only 2.67%. Although the technique is demonstrated with a cuvette appropriate for an extracorporeal circulation in animal experiments, it could possibly be further developed for fiber-optic catheter oximeters.
光纤血氧计通过全血的光学反射来测量氧合血红蛋白饱和度，但此类血氧计的校准依赖于血细胞比容。因此，我们运用光子扩散理论和经验方法，开发出一种新的反射法，可测定血细胞比容并相应校正氧合血红蛋白饱和度测量值。我们的方法采用四根光纤光导、一个光电探测器和三个价格低廉的发光二极管（一个发射波长为660纳米，两个发射波长为813纳米）。血细胞比容由813纳米处不同间距发射光纤的反射率之比确定，并用于校正813 - 660纳米处氧合血红蛋白饱和度的测量值。在红细胞悬液中，血细胞比容反射率测量值与传统测定值之间的平均差异仅为2.09%（r = 0.9），与传统气体容量法测量的氧合血红蛋白饱和度相比，反射法针对不同血细胞比容得出相同的校准曲线，平均差异仅为2.67%。尽管该技术在动物实验中通过适用于体外循环的比色皿得到了验证，但它可能会进一步发展用于光纤导管血氧计。
