Principles Of Operation; Oximetry Overview - Nellcor OxiMax N-595 Operator's Manual

P r i n c i p l e s o f O p e r a t i o n

Oximetry Overview

The N-595 uses pulse oximetry to measure functional oxygen
saturation in the blood. Pulse oximetry works by applying an O M
XI AX
sensor to a pulsating arteriolar vascular bed, such as a finger or toe.
The O M sensor contains a dual light source and a photo detector.
XI AX
Bone, tissue, pigmentation, and venous vessels normally absorb a
constant amount of light over time. The arteriolar bed normally
pulsates and absorbs variable amounts of light during the pulsations.
The ratio of light absorbed is translated into a measurement of
functional oxygen saturation (SpO ).
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Because a measurement of SpO is dependent upon light from the
2
O M sensor, excessive ambient light can interfere with this
XI AX
measurement.
Specific information about ambient conditions, O M sensor
XI AX
application, and patient conditions is contained throughout this
manual.
Pulse oximetry is based on two principles: that oxyhemoglobin and
deoxyhemoglobin differ in their absorption of red and infrared light
(spectrophotometry), and that the volume of arterial blood in tissue
(and hence, light absorption by that blood) changes during the pulse
(plethysmography). A pulse oximeter determines SpO by passing
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red and infrared light into an arteriolar bed and measuring changes in
light absorption during the pulsatile cycle. Red and infrared
low-voltage light-emitting diodes (LED) in the oximetry O M
XI AX
sensor serve as light sources; a photo diode serves as the photo
detector.
Because oxyhemoglobin and deoxyhemoglobin differ in light
absorption, the amount of red and infrared light absorbed by blood is
related to hemoglobin oxygen saturation. To identify the oxygen
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