FM5000C - FM5000PLUS
Maternal/Fetal Monitor
Chapter 17 SpO
2
Monitoring
17.1 Overview
SpO
2
parameters measure blood-oxygen saturation, that is, the percentage of the total oxyhemoglobin. When
97% of the total number of hemoglobin molecules combines with oxygen in the arterial blood’s red blood
cells, this blood will have 97% SpO
2
, and at the same time the monitor reads 97% SpO
2
value. This value
shows the percentage of oxygen-carrying hemoglobin molecules, constituting oxyhemoglobin. Furthermore
parameters of the SpO
2
can also provide pulse rate signal and plethysmography wave (PLETH).
17.1.1 Principle of Measuring SpO
2
Pulse oximetry is a measurement of oxygen saturation. It is a continuous, non-invasive way of determining
the hemoglobin oxygenation saturation. It is involved in measuring how much light emitting from the sensor
side passes through the patient’s tissue (such as a finger or ear) and then reaches the other side of the
receiver.
Though the amount of light passing through depends on many factors, most of them are constant. However,
one of the factors is that blood flow in the arteries changes with time, since it is pulsatile. It is possible to obtain
arterial blood oxygen saturation by measuring the amount of light absorbed during the pulse. And surveying
pulse itself can supply a “PLETH” waveform and pulse rate signal.
The main screen can display “SpO2” value and “PLETH” waveform.
Warning
If there is carbonyl hemoglobin, methemoglobin, or dye dilution chemical present, the SpO2
value will deviate.
17.1.2 Recognition of the type of SpO2 Sensor
The types of SpO2 sensor have been configured when the equipment is delivered from the factory, which is
recognizable by the socket connected to the SpO2 sensor:
Digital SPO2: SpO2 logo marked on the left side of the monitor.
Nellcor SPO2: SpO2 logo and NELLCOR logo marked on the left side of the monitor.
Masimo SPO2: SpO2 logo and MasimoSET logo marked on the left side of the monitor.
The wavelength range and maximum light output power of different transducers are very important
information to clinical doctors, such as, when proceeding photodynamic therapy
Measurable wavelength of analog SpO2 module sensor: red light 660nm, infraredlight 905nm.
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