pulse oximetry
GENERAL DESCRIPTION
Pulse oximetry is a continuous and non-invasive method of measuring the level of arterial
oxygen saturation in blood. The measurement is taken by placing a sensor on a patient,
usually on the fingertip for adults, and the hand or foot for neonates. The sensor is
connected to the pulse oximetry instrument with a patient cable. The sensor collects signal
data from the patient and sends it to the instrument. The instrument displays the calculated
data in three ways: 1) as a percent value for arterial oxygen saturation (SpO
2
), 2) as a pulse
rate (PR) and 3) as a plethysmographic waveform. The following figure shows the general
monitoring setup.
PRINCIPLE OF OPERATION
Pulse oximetry is governed by the following principles:
1. Oxyhemoglobin (oxygenated blood) and deoxyhemoglobin (non-oxygenated blood)
differ in their absorption of red and infrared light (spectrophotometry).
2. The amount of arterial blood in tissue changes with your pulse (photoplethysography).
Therefore, the amount of light absorbed by the varying quantities of arterial blood
changes as well.
The Radical Pulse Oximeter uses a two-wavelength pulsatile system to distinguish
between oxygenated and deoxygenated blood. Signal data is obtained by passing red (rd)
(660 nm wavelength) and infrared (ir)(905 nm wavelength) light through a capillary bed
(for example a fingertip, a hand, a foot) and measuring changes in light absorption during
the pulsatile cycle. See figure below. The Radical utilizes a sensor with red and infrared
light-emitting diodes (LEDs) that pass light through the site to a photodiode (photodetector).
The photodetector receives the light, converts it into an electronic signal and sends it, via
a patient cable, to the Radical for calculation.
Once Radical receives the signal from the patient sensor, it utilizes Masimo SET signal
extraction technology for calculation of the patient’s functional oxygen saturation and pulse rate.
overview
4 Radical Signal Extraction Pulse Oximeter Operator’s Manual
1
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