H100B Pulse Oximeter User Manual
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7.1 Pulse Oximetry Measurement
The oximeter uses oximetry to measure functional
oxygen saturation in the blood. Pulse oximetry works by
applying the sensor to a pulsating arteriolar vascular bed,
such as a finger or a toe. The sensor contains a dual light
source and a photonic 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 sensor, excessive
ambient light can interfere with this measurement.
Pulse oximetry is based on two principles:
Oxyhemoglobin and deoxyhemoglobin differ
in their absorption of red and infrared light
(spectrophotometry).
The volume of arterial blood in tissue (hence
light absorption by the blood) changes during
the pulse (plethysmography).
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