Roche cobas b 123 User Manual

Roche Diagnostics
114 Instructions for Use · Version 13.0
4 Theoretical foundations cobas b 123 POC system
Oximeter module (optional)
Oximeter module (optional)
This module is included in the cobas b 123 <3> POC system and
cobas b 123 <4> POC system variants.
The oximeter module is an optical sensor module for determining total hemoglobin
(tHb), hemoglobin derivatives oxyhemoglobin (O
2
Hb), deoxyhemoglobin (HHb),
carboxyhemoglobin (COHb), methemoglobin (MetHb), and neonatal bilirubin
(Bili).
Functional principle
Hemoglobin derivatives and bilirubin are determined spectrophotometrically based
on the Lambert-Beer law.
* C * d
where,
The basic components of the optical system are:
o Light source (LED)
o Hemolyzer
o Cuvette
o Polychromator
Emitted light from a white light LED is guided to the cuvette. In the cuvette, the light
is partially absorbed by the sample and partially allowed to pass through. The light
that has passed through the cuvette is guided through a light guide to the
polychromator, where it is divided and mapped onto the surface of a photosensitive
receiver (CCD). An electric signal in the photosensitive receiver is generated, which is
used to calculate the absorption and the parameter’s concentrations.
Preanalytical issues can affect the amount of light absorbed by the sample, and thus
influence your results. To avoid these issues, follow appropriate sample collection
procedures.
u Sample collection (p. 139)
Measured bilirubin concentrations from whole blood samples are converted to
plasma concentrations at specific hematocrit levels. Hematocrit levels are determined
from the amount of total hemoglobin.
Samples are hemolyzed inside the cuvette to minimize light scattering from red blood
cells. Hemolysis applies a strong ultrasonic field to samples, in order to rupture red
blood cells and release hemoglobin.
Some limitations also apply for the optical determination of hemoglobin derivatives.
All substances, other than hemoglobin derivatives that absorb or scatter light affect
results. Some examples of these substances are diagnostic or therapeutic dyes, such as
cardio green and methylene blue, and high concentrations of fatty emulsions, such as
Liposyn.
A()
Absorption value, A, at each wavelength, 
()
Absorption coefficient for individual components, at each wavelength 
C
Concentration value of the component
d
Cuvette layer thickness

Roche cobas b 123 Specifications

General

Brand	Roche
Model	cobas b 123
Category	Medical Equipment
Language	English