Datex-Ohmeda F-LM1 Technical Reference Manual page 142

Datex-Ohmeda S/5 Light Monitor
SaO 2 frac = HbO 2 /(HbO 2 + Hb + Dyshemoglobin),
or against functional saturation SaO 2 func,
SaO 2 func = HbO 2 /(HbO 2 + Hb),
which is more insensitive to changes of carboxyhemoglobin and methemoglobin concentrations in
blood.
The oxygen saturation percentage SpO 2 measured by Datex-Ohmeda module is calibrated against
the functional saturation SaO 2 func. The advantage of this method is that the accuracy of SpO 2
measurement relative to SaO 2 func can be maintained even at rather high concentrations of
carboxyhemoglobin in blood. Independent of the calibration method, pulse oximeter is not able to
correctly measure oxygen content of the arterial blood at elevated carboxyhemoglobin or
methemoglobin levels.
Plethysmographic pulse wave
The plethysmographic waveform is derived from the IR signal and reflects the blood pulsation at the
measuring site. Thus the amplitude of the waveform represents the perfusion.
Pulse rate
The pulse rate calculation is done by peak detection of the plethysmographic pulse wave. The
signals are filtered to reduce noise and checked to separate artifacts.
Sensor
The standard sensor is a finger clamp sensor which contains the light source LEDs in one half and
the photodiode detector in the other half. Different kinds of sensors are available from
GE Healthcare.
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