Chapter 4 – PRINCIPLES OF OPERATION
4-1
Alaris
®
SpO
2
Modules
Technical Service Manual
4.1 INTRODUCTION
This chapter describes the
S
p
O
2
Module
principles of operation.
Reference the PC Unit / Pump Module
(
8000
/
8100
Series) Technical Service Manual
for Alaris
®
System principles of operation.
4.2 GENERAL
INFORMATION
S
p
O
2
Module operation is based
on the principles of pulse oximetry.
Oxyhemoglobin and deoxyhemoglobin differ
in their absorption of red and infrared light
(spectrophotometry). The volume of arterial
blood in tissue and the light absorbed
by the blood changes during the pulse
(plethysmography).
Because oxyhemoglobin and
deoxyhemoglobin differ in light absorption,
the amount of red and infrared light
absorbed by blood is related to hemoglobin
oxygen saturation.
4.3
8210 Series (Nellcor Technology)
A pulse oximeter determines
S
p
O
2
by
passing 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 sensor serve as
light sources; a photo diode serves as the
photo detector.
To identify the oxygen saturation of arterial
hemoglobin, the monitor uses the pulsatile
nature of arterial flow. During systole,
a new pulse of arterial blood enters the
vascular bed, and blood volume and light
absorption increase. During diastole, blood
volume and light absorption reach their
lowest point. The
S
p
O
2
Module bases its
S
p
O
2
measurements on the difference
between maximum and minimum absorption
(measurements at systole and diastole).
Summary of Contents for Alaris 8210 Series
Page 55: ......
