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Chapter 10 Monitoring Oxygen Saturaon (SpO
2
)
10.1 Introducon
The funconal oxygen saturaon (SpO
2
) - a percentage of the hemoglobin that can transport oxygen, is monitored by this
device via a non-invasive opcal technique. Based on the principle that oxygenated hemoglobin (HbO
2
) and deoxygenated
hemoglobin (Hb) have dierent absorpon character in the spectrum range from red to infrared light, the device measures
the amount of oxygenated hemoglobin and pulse rate by measuring the absorpon of selected wavelengths of light. The
light generated in the probe passes through the ssue and is converted into electrical signals by the photo-detector in
the probe. The SpO
2
module processes the electrical signals and gives out waveform data and digital values for SpO
2
and
pulse rate displayed on the screen.
10.2 Safety Informaon
Connuous use of ngerp SpO
2
sensor may result in discomfort or pain, especially for those paents with
microcirculatory problem. It is recommended that the sensor should NOT be applied to the same site for over
two hours, please inspect the monitoring site every 1~2 hours for skin integrity, and change the measuring site
periodically if necessary.
Check SpO
2
probe applicaon site periodically (every 30 minutes) to determine circulaon, posioning and skin
sensivity.
SpO
2
measuring site must be examined more carefully for some special paent. Do NOT place the SpO
2
sensor on
the nger with edema or fragile ssue.
Avoid placing the SpO
2
sensor on the same extremity with an arterial catheter, blood pressure cu, or intravascular
infusion line, otherwise the blood ow could be interrupted by the cu or the circulatory condion could make
low blood perfusion so that would result in no pulse found or loss of pulse during SpO
2
monitoring and further
cause false alarm.
The SpO
2
measurement of this monitor may not work eecvely for all kinds of paents, for whose with weak
pulse due to shock, low ambient/body temperature, major bleeding, or use of vascular contracng drug, the
measurement will be more sensive to interference, if stable readings cannot be obtained at any me, disconnue
use of SpO
2
monitoring funcon.
For those with a substanal amount of staining diluon drug (such as methylene blue, indigo green and acid
indigo blue), or carbon monoxide hemoglobin (COHb), or methionine (Me+Hb) or thiosalicylic hemoglobin, and
some with icterus problem, the SpO
2
determinaon by this monitor may be inaccurate.
The drugs such as dopamine, procaine, prilocaine, lidocaine and butacaine may also be a major factor blamed for
serious error of SpO
2
measurements.
Excessive ambient light may aect the measuring result, it includes uorescent lamp, dual ruby light, infrared
heater, and direct sunlight etc.
As the SpO
2
value serves as a reference value for judgment of anemic anoxia and toxic anoxia, the measurement
result of some paents with serious anemia may also present as good SpO
2
value.
Do not apply tape to secure the sensor in place or to tape it shut; venous pulsaon may lead to inaccurate oxygen
saturaon measurements.