Nellcor Oximax NPB-40, Руководство оператора

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NPB-40 119
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
XI
M
AX
sensor to a pulsating arteriolar
vascular bed, such as a finger or toe. The O
XI
M
AX
sensor
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
2
).
Because a measurement of SpO
2
is dependent upon light
from the O
XI
M
AX
sensor, excessive ambient light can
interfere with this measurement.
Specific information about ambient conditions, O
XI
M
AX
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
2
by passing red and infrared light into an arteriolar bed
and measuring changes in light absorption during the