Rad-8 Signal Extraction Pulse Oximeter Operator’s Manual
1-5
1
o v e r v i e w
o v e r v i e w
1-4
Rad-8 Signal Extraction Pulse Oximeter Operator’s Manual
1
FUNCTIONAL VS. FRACTIONAL SATURATION
The Rad-8 is calibrated to measure and display functional saturation which is the amount of
oxygenated hemoglobin expressed as a percentage of the hemoglobin that can transport
oxygen. The Rad-8 does not measure fractional saturation which is oxygenated hemo-
globin expressed as a percentage of all measured hemoglobin
.
This includes measured
dysfunctional hemoglobin such as carboxyhemoglobin or methemoglobin. To convert
fractional saturation to functional saturation, the fractional saturation measurements must
be converted according to:
Functional saturation =
Fractional saturation
x 100
100 - (% carboxyhemo % methemoglobin)
MEASURED VS. CALCULATED SATURATION
Oxygen saturation measurements obtained from a pulse oximeter are commonly com-
pared to saturations calculated from the partial pressure of oxygen (PO
2
) obtained from
an arterial blood gas sample. When comparing the two measurements and interpreting
values, caution should be used, as the calculated value obtained from the blood gas
sample may differ from the SpO
2
measurement of the pulse oximeter. Different results are
usually obtained from the blood gas sample if the calculated saturation is not appropriately
corrected for the effects of variables that shift the relationship between PO
2
and satura-
tion, such as: pH, temperature, the partial pressure of carbon dioxide (PCO
2
), 2,3-DPG,
and fetal hemoglobin. Also, as blood gas samples are usually taken over a period of 20
seconds (the time it takes to draw 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 mov-
ing (pulsating) in the measurement site. During patient motion, however, the non-arterial
blood also moves, causing 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 physi-
ologic 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 connects
to the pulse oximetry instrument directly or 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 two ways:
1
. As a percent value for arterial oxygen saturation (SpO
2
) and
2
. As a pulse rate (PR).
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 (photoplethysogra-
phy). Therefore, the amount of light absorbed by the varying quantities of arterial
blood changes as well.
The Rad-8 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 or 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 Rad-8 utilizes a sensor with red and infrared
light-emitting diodes (LEDs) that pass light through the site to a photodiode (photodetec-
tor). The photodetector receives the light, converts it into an electronic signal and sends it
to the Rad-8 for calculation.
Once the Rad-8 receives the signal from the sensor, it utilizes Masimo SET signal extrac-
tion technology for calculation of the patient’s functional oxygen saturation and pulse rate.
The maximum of the skin surface temperature is measured at an ambient temperature of
less than 106º F (41º C).This is verified by Masimo sensor skin temperature test proce-
dures.
1. Instrument
2. Patient
Cable
3. Sensor
2
3
1
1. Light Emitting Diodes (LEDs)
2. Recessed Photo Detector
2
1
