Rad-57 Signal Extraction Pulse CO-Oximeter Operator’s Manual 1-7
1
Rad-57 Signal Extraction Pulse CO-Oximeter Operator’s Manual
1
overview
FUNCTIONAL VS. FRACTIONAL SATURATION
The Rad-57 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. Note that carboxyhemoglobin is not capable of transporting oxygen, but
is recognized as oxygenated hemoglobin by conventional pulse oximetry.
MEASURED VS. CALCULATED VALUES
SpO
2
, SpCO* and SpMet* measurements that can be obtained from the Rad-57 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
, SpCO and SpMet measurements of the Pulse CO-Oximeter. In the case
of SpO
2
, 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. In the case of SpCO and SpMet, in addition to the effects of temperature and
pH, different results are also expected if concentration of methemoglobin in the blood gas
sample are abnormal (less than 90% for arterial oxygen saturation, and greater than 2%
for methemoglobin concentration). 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 oxygen saturation, carboxyhemoglobin and methemoglobin concentration of
the patient are stable and not changing over the period of time that the blood gas sample
is taken.
MASIMO SET SIGNAL EXTRACTION TECHNOLOGY FOR SpO
2
MEASUREMENTS
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, 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 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.
SpCO AND SpMet MEASUREMENTS DURING PATIENT MOTION
The Rad-57 displays measurements of SpCO* and SpMet* during patient motion. However,
because of the changes in the physiological parameters such as blood volume, arterial-
venous coupling, etc. that occur during patient motion, the accuracy of such measurements
may not be readable during excessive motion.
* See Model Summary for applicable device.
To Next Page
Loading...
