FUNCTIONAL VS. FRACTIONAL SATURATION
The Radical measures and displays functional saturation: the amount of oxygenated
hemoglobin expressed as a percentage of the hemoglobin that can transport oxygen. The
Radical does not measure fractional saturation: oxygenated hemoglobin expressed as a
percentage of all measured hemoglobin, including 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 - (% carboxyhemoglobin + % methemoglobin)
MEASURED VS. CALCULATED SATURATION
Oxygen saturation measurements obtained from a pulse oximeter are commonly
compared to saturations calculated from the partial pressure of oxygen (PO
2
) obtained
from an arterial blood gas sample. When comparing the two measurements, caution
should be used when interpreting the values, 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 saturation, 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 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 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. Masimo SET signal processing algorithm, Discrete Saturation Transform
TM
(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.
Radical Signal Extraction Pulse Oximeter Operator’s Manual 5
1
overview
Masimo SET DST
Komentáře k této Příručce