69
II Common Knowledge
1 Meaning of SpO
SpO
is the saturation percentage of oxygen in the blood, so called O2 concentra-
2
tion in the blood; it is defined by the percentage of oxyhemoglobin (HbO
total hemoglobin of the arterial blood. SpO
parameter to 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 hemoglo-
2
bins which release oxygen.
2 Principle of Measurement
Based on Lamber-Beer law, the light absorbance of a given substance is directly
proportional with its density or concentration. When the light with certain wave-
length 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
have different absorption character in the spectrum range from red to infrared
light (600nm~1000nm wavelength), by using these characteristics, SpO
determined. SpO
-- a percentage of the hemoglobin that can transport oxygen. In contrast, he-
moximeters report fractional oxygen saturation – a percentage of all measured
hemoglobin, including dysfunctional hemoglobin, such as carboxyhemoglobin or
metahemoglobin.
Clinical application of pulse oximeters: SpO
meter to reflect the respiration and ventilation function, so SpO
in clinical 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
the hypoxemia patient earlier, thereby preventing or reducing accidental death
caused by hypoxia effectively.
3 Normal SpO
2
In campagna area, healthy people's SpO
below 94% are determined as hypoxia. SpO
threshold for determining anoxia by most researchers, so SpO
the oximeter 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, fluo-
rescent lights, infrared heating lamps, or direct sunlight.
2
+Hb)×100%
2
measured by this oximeter is the functional oxygen saturation
2
can be determined in time by measurement and find
2
Range and Default Low Limit
accuracy (interference reason)
2
ENGLISH
is an important physiological
2
) and deoxygenated hemoglobin (Hb)
2
is an important physiological para-
2
value is greater than 94%, so the values
2
<90% is considered as the default
2
) in the
2
can be
2
monitoring used
2
low limit of
2