Radical Signal Extraction Pulse Oximeter Operator’s Manual
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FUNCTIONAL SATURATION
The Radical is calibrated to measure and display functional saturation (SpO
2
): the
amount of oxyhemoglobin expressed as a percentage of the hemoglobin that is available
to transport oxygen.
MEASURED VS. CALCULATED SATURATION
Oxygen measurements that can be obtained from the Radical are commonly compared
to invasive measurements obtained from blood gas samples. When comparing invasive
and noninvasive measurements and interpreting values, caution should be used, as the
calculated values obtained from the blood gas sample may differ from the SpO
2
measurements of the pulse oximeter. Different results are usually obtained from the
arterial blood gas sample if the calculated measurement is not appropriately corrected
for the effects of variables that shift the relationship between the partial pressure of
oxygen (PO2) and saturation, such as: pH, temperature, the partial pressure of carbon
dioxide (PCO2), 2,3-DPG, and fetal hemoglobin. As blood gas samples are usually taken
over a period of 20 seconds (the time it takes to draw the blood) a meaningful
comparison can only be achieved if the core oxygen saturation of the patient is stable
and not changing over the period of time that the blood gas sample is taken.
MASIMO SET SIGNAL EXTRACTION TECHNOLOGY
Masimo Signal Extraction Technology’s signal processing differs from conventional pulse
oximeters. Conventional pulse oximeters assume that arterial blood is the only blood
moving (pulsating) in the measurement site. During patient motion, however, the non-
arterial blood also moves, which causes conventional pulse oximeters to read low values,
because they cannot distinguish between the arterial and venous blood movement
(sometimes referred to as noise). Masimo SET pulse oximetry utilizes parallel engines and
adaptive digital filtering. Adaptive filters are powerful because they are able to adapt to the
varying physiologic signals and/or noise and separate them by looking at the whole signal
and breaking it down to its fundamental components. The Masimo SET signal processing
algorithm, Discrete Saturation Transform
®
(DST)
®
, reliably identifies the noise, isolates it
and, using adaptive filters, cancels it. It then reports the true arterial oxygen saturation for
display on the monitor.
P u l s e o x i m e t r y
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)
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
distinguishbetween oxygenated and deoxygenated blood. Signal data is obtained by
passing red(rd)(660 nm wavelength) and infrared (ir)(905 nm wavelength) light through
a vascular bed (for example a fingertip, a hand, a foot) and measuring changes in light
absorption during the pulsatile cycle. This information may be useful to clinicians. The
radiant power of the light is rated at 0.79mW (max.). 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 to the Radical for calculation.
Once the Radical receives the signal from the sensor, it utilizes Masimo SET signal extraction
technology for calculation of the patient’s functional oxygen saturation and pulse rate.
Recessed
Photo Detector
LED's
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Radical Signal Extraction Pulse Oximeter Operator’s Manual
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1.
Instrument
2.
Patient Cable
3.
Sensor
