Chapter 8: Oximetry
8-2 VS2000 Vital Signs Monitor Operation Manual
WARNING! Use only SpO
2
sensors supplied with, or specifically intended
for use with, this device.
WARNING! SpO
2
measurements may be adversely affected in the presence
of high ambient light. Shield the sensor area (with a surgical
towel, for example) if necessary.
WARNING! Dyes introduced into the bloodstream, such as methylene blue,
indocyanine green, indigo carmine, patent blue (PBV), and
fluorescein may adversely affect the accuracy of the SpO
2
reading.
WARNING! Any condition that restricts blood flow, such as use of a blood
pressure cuff or extremes in systemic vascular resistance, may
cause an inability to determine accurate SpO
2
and pulse rate
readings.
CAUTION! Unplug the sensor from the monitor before cleaning or
disinfecting.
NOTE! Obstructions or dirt on the sensor's red light or detector may cause
a sensor failure. Make sure there are no obstructions and the
sensor is clean.
8.3 Pulse Oximetry Theory of Operation
The pulse oximeter determines %SpO
2
and pulse rate by passing two
wavelengths of low intensity light, one red and one infrared, through body
tissue to a photodetector. Information about wavelength range can be
especially useful to clinicians. Wavelength information for this device can be
found in the SpO
2
Specifications section of this manual.
Pulse identification is accomplished by using plethysmographic techniques,
and oxygen saturation measurements are determined using
spectrophotometric oximetry principles. During measurement, the signal
strength resulting from each light source depends on the color and thickness
of the body tissue, the sensor placement, the intensity of the light sources,
and the absorption of the arterial and venous blood (including the time
varying effects of the pulse) in the body tissues.
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