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II. Common Knowledge
1 Meaning of SpO
SpO
is the saturation percentage of oxygen in the blood, so called O2 concentration
2
in the blood; it is defined by the percentage of oxyhemoglobin ( HbO
hemoglobin of the arterial blood. SpO
reflect the respiration function; it is calculated by the following method:
SpO
= HbO
/ (HbO
2
2
HbO
are the oxyhemoglobins (oxygenized hemoglobin), Hb are those hemoglobins
2
which release oxygen.
2 Principle of Measurement
Based on Lamber-Beer law, the light absorbance of a given substance is directly pro-
portional with its density or concentration. When the light with certain wavelength
emits on human tissue, the measured intensity of light after absorption, reflecting and
attenuation in tissue can reflect the structure character of the tissue by which the light
passes. Due to that oxygenated hemoglobin (HbO
(Hb) have different absorption character in the spectrum range from red to infrared
light (600nm~1000nm wavelength), by using these characteristics, SpO
termined. SpO
2
percentage of the hemoglobin that can transport oxygen. In contrast, hemoximeters
report fractional oxygen saturation – a percentage of all measured hemoglobin, in-
cluding dysfunctional hemoglobin, such as carboxyhemoglobin or metahemoglobin.
Clinical application of pulse oximeters: SpO
to reflect the respiration and ventilation function, so SpO
cal becomes more popularly, such as monitoring the patient with serious respiratory
disease, the patient under anesthesia during operation, premature and neonate. The
status of SpO
can be determined in time by measurement and find the hypoxemia
2
patient earlier, thereby preventing or reducing accidental death caused by hypoxia
effectively.
3 Normal SpO
Range and Default Low Limit
2
In campagna area, healthy people's SpO
ues be low 94% are determined as hypoxia. SpO
threshold for determining anoxia by most researchers, so SpO
ter is set as 90% generally.
4 Factors affecting SpO
• Intravascular dyes such as indocyanine green or methylene blue.
• Exposure to excessive illumination, such as surgical lamps, bilirubin lamps, fluores-
cent lights, infrared heating lamps, or direct sunlight.
• Vascular dyes or external used color-up product such as nail enamel or color skin
care.
2
+Hb)×100%
2
measured by this oximeter is the functional oxygen saturation -- a
accuracy (interference reason)
2
ENGLISH
is an important physiological parameter to
2
) and deoxygenated hemoglobin
2
is an important physiological parameter
2
value is greater than 94%, so the val-
2
<90% is considered as the default
2
) in the total
2
can be de-
2
monitoring used in clini-
2
low limit of the oxime-
2
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