User manual
With (4.3) it is possible to calculate a theoretical conversion curve between the R ratio
and oxygen saturation in arterial blood
S
a
O
2
(Fig. 4.4), which is used in calibrating pulse
oxymeters. By performing comparative measurements of O
2
saturation via the pulse oxymeter
and blood gas analyzer, it is possible to create the so called empirical conversion curve. The
conversion curve may be approximated by a linear equation, which may be used to calculate
the O
2
saturation. The resulting value of oxygen saturation in arterial blood S
a
O
2
measured by
the pulse oxymeter is marked as
S
p
O
2
.
Thecontentsandtheaimofthemeasurements
Pulse oxymeters are diagnostic medical devices, which allow for monitoring of
oxygen saturation in arterial blood. The devices are based on an optical principle, when
radiation (light) is transmitted through vascular tissue. We measure the loss of the radiation
(light) intensity in two wavelengths, which is absorbed by hemoglobin contained in
erythrocytes. Depending on the representation of oxy-hemoglobin and deoxy-hemoglobin in
blood, both the radiations with different wavelengths are absorbed in different rates. The aim
of the measurement is to get acquainted with the function of pulse oxymeters and to verify
their correct functioning by means of a SpO
2
simulator, and further on to verify and measure
managing and sensed signals on an analogous pulse oxymeter.
Measurementtasks
1. Use the SpO
2
simulator [4.5] to verify the correctness of measured values in several
types of pulse oxymeters. Compare and record the set and the measured values.
2.
Use the analogue pulse oxymeter and via an oscilloscope display the signal courses in
the check points K1-K12, see Fig. 4.5.
3.
Measure the voltage size R/IR in the check points K9, K10 and K13, K14 by means of
a digital voltmeter (multimeter), use them in an equation 2 and calculate the ratio R,
and read the particular saturation value from a curve in Fig. 4.4.
4.
Use edutools for sensing the plethysmographic curve to display the plethysmographic
curve on the oscilloscope and watch how its shape changes in held breath and under
the influence of movement artefacts. Read the size of heart frequency from the
plethysmographic curve; draw the course of the plethysmographic curve.
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