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Technical Discussion
N-560 Service Manual
105
T e c h n i c a l D i s c u s s i o n
Oximetry Overview
The N-560 Pulse Oximeter measures functional oxygen saturation by
measuring the light absorption of tissue, bone, and blood during the pulsatile
cycle. Red and infrared sensor LED’s are used as light sources. A photodiode,
acting as a photodetector, senses each received wavelength of light; namely,
incident light less the amount absorbed by tissue, for both the red and infrared
channels. It also feeds corresponding electrical signals from the sensor to the
N-560. These signals are then processed by the N-560 software engine to
produce SpO
2
and pulse rate data. 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 sensor,
excessive ambient light can interfere with this measurement.
Specific information about ambient conditions, 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 (i.e.,
spectrophotometry), and that the volume of arterial blood in tissue (and hence,
light absorption by that blood) changes during the pulse (i.e.,
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 pulsatile cycle. Red and infrared low-voltage light-emitting diodes
(LED) in the oximetry sensor serve as light sources; a photodiode 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 saturation of arterial hemoglobin,
the N-560 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 N-560 bases its SpO
2
measurements on the difference
between maximum and minimum absorption (i.e., measurements at systole
and diastole). By doing so, it focuses on light absorption by pulsatile arterial
blood, eliminating the effects of nonpulsatile absorbers such as tissue, bone,
and venous blood.
Summary of Contents for Nellcor OxiMax N-560
Page 1: ...Service Manual OxiMaxTM Technology Nellcor OxiMax N 560 Pulse Oximeter TM...
Page 10: ...List of Tables N 560 Service Manual viii...
Page 38: ...Performance Verification 28...
Page 80: ...Disassembly Guide 70 Figure 41 Equipotential Ground Terminal Removed...
Page 83: ...Spare Parts N 560 Service Manual 73 Figure 42 Exploded View...
Page 84: ...Spare Parts 74...
Page 88: ...Packing for Shipment 78...
Page 104: ...Specifications 94...
Page 114: ...Data Port Interface Protocol 104...
Page 128: ...Technical Discussion 118...
Page 130: ...Technical Discussion 120...
Page 132: ...Technical Discussion 122...
Page 134: ...Technical Discussion 124...
Page 136: ...Technical Discussion 126...
Page 138: ...Technical Discussion 128...
Page 139: ...Technical Discussion N 560 Service Manual 129 Figure 55 Main PCB Parts Locator Diagram...
Page 140: ...Technical Discussion 130...
Page 142: ...Technical Discussion 132...
Page 144: ...Technical Discussion 134...
Page 146: ...Technical Discussion 136...
Page 147: ...Technical Discussion N 560 Service Manual 137 Figure 59 Front Panel Parts Locator Diagram...
Page 148: ...Technical Discussion 138...
Page 149: ...Technical Discussion N 560 Service Manual 139 Figure 60 Power Supply Schematic Diagram...
Page 150: ...Technical Discussion 140...
Page 151: ...Technical Discussion N 560 Service Manual 141 Figure 61 Power Supply Parts Locator Diagram...
Page 152: ...Technical Discussion 142...
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