Rad-97
Chapter 1: Technology Overview
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Once Rad-97 receives the signal from the sensor, it utilizes proprietary algorithms to
calculate the patient’s functional oxygen saturation (SpO
2
[%]), blood levels of
carboxyhemoglobin saturation (SpCO [%]), methemoglobin saturation (SpMet [%]), total
hemoglobin concentration (SpHb [g/dL]) and pulse rate (PR). The SpCO, SpMet and SpHb
measurements rely on a multi-wavelength calibration equation to quantify the percentage of
carbon monoxide and methemoglobin and the concentration of total hemoglobin in arterial
blood. Maximum skin-sensor interface temperature was tested to be less than 41º C (106º F)
in a minimum ambient temperature of 35º C (95º F). The tests were conducted with sensors
operating at reasonable worst case power.
Pulse CO-Oximetry vs. Drawn Whole Blood Measurements
When SpO
2
, SpCO, SpMet, and SpHb measurements obtained from the Rad-97 (noninvasive)
are compared to drawn whole blood (invasive) measurements by blood gas and/or laboratory
CO-Oximetry methods, caution should be taken when evaluating and interpreting the results.
The blood gas and/or laboratory CO-Oximetry measurements may differ from the SpO
2
, SpCO,
SpMet, SpHb, and SpOC measurements of the Rad-97. Any comparisons should be
simultaneous, meaning the measurement on the device should be noted at the exact time
that blood is drawn.
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 (pO
2
) and saturation, such as:
pH,temperature, the partial pressure of carbon dioxide (pCO
2
), 2,3-DPG, and fetal hemoglobin.
In the case of SpCO, different results are also expected if the level of methemoglobin (MetHb)
in the blood gas sample is abnormal (greater than 2% for MetHb).
In the case of SpHb, variation in hemoglobin measurements may be profound and may be
affected by sampling technique as well as the patient's physiological conditions. Any results
exhibiting inconsistency with the patient's clinical status should be repeated and/or
supplemented with additional test data. As with most hemoglobin tests, a laboratory blood
sample should be analyzed prior to clinical decision making.
High levels of bilirubin may cause erroneous SpO
2
, SpMet, SpCO, and SpHb readings. As blood
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 (SaO
2
), levels of
carboxyhemoglobin (COHb), and MetHb of the patient are stable and not changing over the
period of time that the blood gas sample is taken. Subsequently, blood gas and laboratory
CO-Oximetry measurements of SpO
2
, SpCO, SpMet, SpHb, and SpOC may vary with the rapid
administration of fluids and in procedures such as dialysis. Additionally, drawn whole blood
testing can be affected by sample handling methods and time elapsed between blood draw
and sample testing.
Measurements with Low Signal IQ should not be compared to laboratory measurements.
General Description for Total Hemoglobin (SpHb)
Pulse CO-Oximetry is a continuous and noninvasive method of measuring the levels of total
hemoglobin (SpHb) in arterial blood. It relies on the same principles of pulse oximetry to
make its SpHb measurement.
