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Chapter VII SpO2 Measurement
7.1 SpO2 Monitor instruction
7.1.1 SpO2 Definition
SpO2 plethysmography measure arterial oxygen saturation, which is the percentage
of total oxygenated haemoglobin. For example, if 97% of the total haemoglobin
molecules in the red blood cells of arterial blood are combined with oxygen, the blood
will have 97% SpO2 oxygen saturation, and the SpO2 value reading on the monitor
should be 97%. The SpO2 value shows the percentage of oxygen carrying
haemoglobin molecules forming oxyhaemoglobin. SpO2 plethysmography can also
provide pulse rate signal and plethysmography wave.
7.1.2 Measurement Principle of SpO2 Plethysmography
Blood oxygen saturation was measured by pulse oximetry. This is a continuous and
non-invasive method for measuring haemoglobin oxygenation saturation.
It measures how much light emitted from one side of the sensor light source passes
through animal tissues (such as ears, tongue, etc.) and reaches the receiver of the
other side.
The wavelength that the sensor can measure is usually 660nm for red LED and
940nm for infrared LED. The maximum optional output power of LED is 4MW.
The amount of light passing through depends on a number of factors, most of which
are constant. But one of these factors, arterial blood flow, changes over time
because it's pulsating. By measuring the light absorbed during pulsation, it is
possible to obtain arterial blood oxygen saturation. The detection of pulse itself can
give a plethysmography waveform and pulse rate signal.
The SpO2 value and plethysmography waveform can be displayed on the main
screen.
Warning
If carboxyhaemoglobin, methaemoglobin or dye dilution chemicals are present, the
SpO2 value will deviate.
7.1.3 Measurement of SpO2 Plethysmography Parameters
The 'SpO2' value and waveform can be displayed on the main screen.
Warning
If carboxyhaemoglobin, methaemoglobin or dye dilution chemicals are present, the
SpO2 value will deviate. Oxygen saturation / pulse monitoring.
Warning
The cable of the electrosurgical equipment should not be entangled with the sensor
cable.
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