User's Manual

Radical-7 Chapter 1: Technology Overview
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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. Subsequently, blood gas
and laboratory CO-Oximetry measurements of SpO2, 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. The measurement is taken by a sensor capable of measuring
SpHb, usually on the fingertip for adult and pediatric patients.
The sensor connects directly to the Pulse CO-Oximeter 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 as measurement of total hemoglobin concentration.
Successful Monitoring for SpHb
A stable SpHb reading is associated with correct sensor placement, small physiological
changes during the measurement and acceptable levels of arterial perfusion at the
measurement site. Physiological changes at the measurement site are mainly caused by
fluctuations in the oxygen saturation, blood concentration and perfusion. See Safety
Information, Warnings, and Cautions on page 11 and Troubleshooting Measurements on
page 111.
General Description for Total Arterial Oxygen Content (CaO2)
Oxygen (O2) is carried in the blood in two forms, either dissolved in plasma or combined with
hemoglobin. The amount of oxygen in the arterial blood is termed the oxygen content (CaO2)
and is measured in units of ml O2/dL blood. One gram of hemoglobin (Hb) can carry 1.34 ml
of oxygen, whereas 100 ml of blood plasma may carry approximately 0.3 ml of oxygen*. The
oxygen content is determined mathematically as:
CaO2 = 1.34 (ml O2/g Hb) x Hb (g/dL) x HbO2 + PaO2 (mm Hg) x (0.3 ml O2/100 mm Hg/dL)
Where HbO2 is the fractional arterial oxygen saturation and PaO2 is the partial pressure of
arterial oxygen.
For typical PaO2 values, the second part of the above equation (PaO2 [mm Hg] x [0.3 ml O2/
100 mm Hg/dL]) is approximately 0.3 ml/dL. Furthermore, for typical carboxyhemoglobin
and methemoglobin levels, the functional saturation (SpO2) as measured by a pulse oximeter
is given by:
SpO2 = 1.02 x HbO2
*Martin, Laurence. All You Really Need to Know to Interpret Arterial Blood Gases, Second
Edition. New York: Lippincott Williams & Wilkins, 1999.