User manual
4. Principles and applications of pulse oxymeters
Theoreticalintroduction
Pulse oxymetry is a non-invasive optical method used for long-term monitoring of
arterial blood’s oxygen saturation. The method is based on measuring the intensity of
radiation (light) transmitted through vascular tissue. This intensity can be calculated via the
Lambert-Beer Law (4.1), which expresses the exponential dependence of the intensity of the
transmitted radiation (light) on the concentration of the solution the radiation (light) passes
through.
)(..
0
.
λε
dc
eII
−
=
(4.1)
I - intensity of the transmitted radiation (light) (W/m
2
), I
0
- intensity of incident radiation
(light) (W/m
2
), c - concentration of the solution (mol/l), d - thickness of the layer (m) through
which the radiation (light) is transmitted, and ε(λ) - the absorption coefficient (l·mol
-1
·m
-1
),
which depends on the wavelength of the transmitted radiation (light).
The exponential decrease of the radiation (light) depending on the thickness of the
layer the radiation (light) is transmitted through, is demonstrated in Fig. 4.1.
Fig. 4.1: Absorption of radiation (light) in the tissue.
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