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Chapter12 SpO
2
Monitoring
12.1 What is SpO
2
Monitoring
SpO
2
Plethysmogram measurement is employed to determine the oxygen saturation of hemoglobin in the arterial blood.
If, for example, 97% hemoglobin molecules in the red blood cells of the arterial blood combine with oxygen, then the
blood has a SpO
2
oxygen saturation of 97%. The SpO
2
numeric on the monitor will read 97%. The SpO
2
numeric
shows the percentage of hemoglobin molecules which have combined with oxygen molecules to form oxyhemoglobin.
The SpO
2
/PLETH parameter can also provide a pulse rate signal and a plethysmogram wave.
How the SpO
2
/ PLETH Parameter Works
■
Arterial oxygen saturation is measured by a method called pulse oximeter. It is a continuous, non-invasive method
based on the different absorption spectra of reduced hemoglobin and oxyhemoglobin. It measures how much light,
sent from light sources on one side of the sensor, is transmitted through patient tissue (such as a finger or an ear),
to a receiver on the other side.
■
The sensor measurement wavelengths are nominally 660nm for the Red LED and 880nm for Infrared LED.
Maximum optical power output for the Red LED is 6.65 mW and the Infrared LED is 6.75 mW.
■
The amount of light transmitted depends on many factors, most of which are constant. However, one of these
factors, the blood flow in the arteries, varies with time, because it is pulsating. By measuring the light absorption
during a pulsation, it is possible to derive the oxygen saturation of the arterial blood. Detecting the pulsation gives
a PLETH waveform and pulse rate signal.
■
The SpO
2
value and the PLETH waveform can be displayed on the main screen.
■
SpO
2
is a non-invasive measurement of the functional oxygen saturation.
Warning
Pulse oximeter can overestimate the SpO
2
value in the presence of Hb-CO, Met-Hb or dye dilution
chemicals.
ES (Electrosurgery) equipment wire and SpO
2
cable must not be tangled up.
Do not put the sensor on extremities with arterial catheter or venous syringe.
SpO
2
/ Pulse Monitoring
Note
Do not perform SpO
2
measuring and NIBP measuring on same arm at one time, because obstruction of
blood flow during NIBP measuring may adversely affect the reading of SpO
2
value.
12.2 Precautions during SpO
2
/Pulse Monitoring
Note
Make sure the nail covers the light window;
The wire should be on the backside of the hand.
SpO2 value is always displayed at the same position.
SpO2 waveform is not proportional to the pulse volume.
Please read the measured value when the waveform on screen is equably and steady-going, This measured
value is optimal value. And the waveform at the moment is the standard one.
Pulse Rate will be displayed only under following situations:
◆
Select HR FROM as "SpO
2
" or “BOTH” in the ECG SETUP menu.
◆
Select HR FROM as “AUTO” in the ECG SETUP menu and there is no ECG signal.
Warning
Check if the sensor cable is in normal condition before monitoring. After unplugging the SpO
2
sensor cable
from the socket, the system shall display the error message “SpO
2
SENSOR OFF” and give the audible
alarm.
When operating at the beginning, the operator inserts his finger, and setup the SpO
2
ALM HI lower than
