Spectrophotometric Determination of the Oxygen Saturation

Although Refsum (Rl) has demonstrated that very good results can be achieved using X = 576 and 560 nm (nonisobestic), the methods described (Section 5.1.1) have been chosen because the use of an isobestic wavelength offers distinct advantages (Section 4). 

The constants 3.08 and 1.62 have been calculated from a series of 25 measurements of for 0% HbOa and 100% HbOa the constants 

Hb02 and 11 measurements for 0% HbOa. The series of 17 measurements (100% HbOs) had a mean value of = 1.753 with a standard de- 

In a series of 30 blood samples sent to the clinical laboratory for routine arterial 80, determination, the saturation was determined using both the 

X = 560 and 522 nm and the X = 560 and 506 nm method. The results are given in Table 13. In this table each value of So, is the mean of a duplicate determination. The standard deviations of the duplicate determinations have been calculated for both methods. Using X = 560 and 522 nm a standard deviation of 1.5% saturation was found in the case of X = 560 and 506 nm the standard deviation was 1.4% saturation. The isobestic points were established at X = 522.2 0.2 nm (n = 100) and at X = 506.0 0.4 nm (n = 15), respectively. Finally, when comparing the two methods, the standard deviation of the difference between the corresponding saturation values (Table 13) was calculated at 1.4% saturation. 

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