Principles Of Operation; Oximetry Overview - Nellcor Oximax NPB-40 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 NPB-40 uses pulse oximetry to measure functional
oxygen saturation in the blood. Pulse oximetry works by
applying an O
vascular bed, such as a finger or toe. The O
contains a dual light source and a photo detector.
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
Because a measurement of SpO
from the O
interfere with this measurement.
Specific information about ambient conditions, O
sensor 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 red and infrared light into an arteriolar bed
and measuring changes in light absorption during the
NPB-40
M sensor to a pulsating arteriolar
XI AX
).
2
is dependent upon light
2
M sensor, excessive ambient light can
XI AX
M sensor
XI AX
M
XI AX
2
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