Theory Of Operation - Smiths Medical Finger Oximeter Bedienungsanleitung

Chapter 2: Intended Use and Features

Theory of Operation

The pulse oximeter determines SpO
wavelengths of low intensity 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 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.
Figure 2.1: Theory of Operation
1
2
1) Red and infrared LED light sources
2) Detector
The pulse oximeter processes these signals, separating the time
invariant parameters (tissue thickness, skin color, light intensity, and
venous blood) from the time variant parameters (arterial volume
and SpO ) to identify the pulse rate and calculate oxygen saturation.
2
Oxygen saturation calculations can be performed because oxygen
saturated blood predictably absorbs less red light than oxygen
depleted blood.
Since measurement of SpO
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 pulse and SpO
2-2
and pulse rate by passing two
2
depends on a pulsating vascular bed, any
2
readings.
2
Finger Oximeter Operation Manual