User Manual for Vital Signs Monitor
46
8.3.2 SpO
2
Measurement Restrictions (interference reason)
Intravascular dyes such as indocyanine green or methylene blue
Exposure to excessive illumination, such as surgical lamps, bilirubin lamps, fluorescent lights,
infrared heating lamps, or direct sunlight.
Vascular dyes or external used color-up product such as nail enamel or color skin care
Excessive patient movement
Placement of a sensor on an extremity with a blood pressure cuff, arterial catheter, or intravascular
line
Exposure to the chamber with high pressure oxygen
There is an arterial occlusion proximal to the sensor
Blood vessel contraction caused by peripheral vessel hyperkinesias or body temperature
decreasing
8.3.3 Low SpO
2
measuring value caused by pathology reason
Hypoxemia disease, functional lack of HbO
2
Pigmentation or abnormal oxyhemoglobin level
Abnormal oxyhemoglobin variation
Methemoglobin disease
Sulfhemoglobinemia or arterial occlusion exists near sensor
Obvious venous pulsations
Peripheral arterial pulsation becomes weak
Peripheral blood supply is not enough
8.3.4 Clinical Limitations
As the measure is taken on the basis of arteriole pulse, substantial pulsating blood stream of
subject is required. For a subject with weak pulse due to shock, low ambient/body temperature,
major bleeding, or use of vascular contracting drug, the SpO
2
waveform (PLETH) will decrease. In
this case, the measurement will be more sensitive to interference.
For those with a substantial amount of staining dilution 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
determination 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.
As the SpO
2
value serves as a reference value for judgment of anemic anoxia and toxic anoxia, the
measurement result of some patients with serious anemia may also present as good SpO
2
value.
