Smiths Medical 1818R, Руководство по эксплуатации и обслуживанию

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Chapter 2: General Description
2-4 Oximeter Operation and Service Manual
Theory of Operation
The oximeter determines SpO
2
and pulse rate by passing two wavelengths
of light, one red and one infrared, through body tissue to a photodetector.
During measurement, the signal strength resulting from each light source
depends on the color and thickness of the body tissue, the sensor place-
ment, 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.
The oximeter processes these signals, separating the time invariant parame-
ters (tissue thickness, skin color, light intensity, and venous blood) from the
time variant parameters (arterial volume and SpO
2
) to identify the pulse
rate and calculate oxygen saturation. Oxygen saturation calculations can be
performed because oxygen saturated blood predictably absorbs less red
light than oxygen depleted blood.
Figure 2-2: Oximetry Theory of Operation
Low intensity red and infrared LED light sources
Detector