Rapidlab 1200 Operator’s Guide: System Overview and Intended Use 1-51
02087462 Rev. V
Sulfhemoglobin
Sulfhemoglobin (SulfHb) is a stable compound of hemoglobin and sulfur. This is
a fraction of hemoglobin that cannot deliver oxygen to body tissues and may be
elevated in some patients taking sulfur-containing drugs or with certain
infections.
26
Sulfhemoglobin has an extremely low affinity for oxygen and may
often be accompanied by methemoglobinemia. The presence of sulfhemoglobin
affects oxyhemoglobin values and other quantities if its absorbance spectrum is
not accounted for.
19
The sulfhemoglobin reference range for a normal population
is 0.0 to 2.2%.
The CO-oximeter (CO-ox) module detects and indica
tes concentrations of
sulfhemoglobin greater than 1.5%.
Determination of Hemoglobin Derivatives
Hemoglobin derivatives have characteristic absorbance spectra. Each derivative
absorbs light differently at different wavelengths. Similarly, interfering substances
also absorb light at known wavelengths.
The spectral absorption method determines concentration using
matrix equations.
For each substance or fraction, the absorbance at a specific wavelength is equal to
the product of the path length, concentration of the fraction or substance, and the
molar absorptivity or the extinction coefficient for that substance, as shown in the
following equation:
A
x
= ε
1
C
1
+ ε
2
C
2
+... ε
n
C
n
where A
x
is the absorbance at a specific wavelength, ε is the major extinction
coefficient for that fraction or substance at a specific wavelength, and C is the
concentration of the substance.
These equations are based on the work of
VanAssendelft
28, 29
and Benesch,
Benesch, and Yung.
29
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