F-54 624074/07
F Pulse oximetry
simulator. This variation equals plus or minus one standard deviation, which
encompasses 68% of the population.
6. SpHb accuracy has been validated on healthy adult male and female
volunteers and on surgical patients with light to dark skin pigmentation in
the range of 8-17 g/dl SpHb against a laboratory CO-oximeter. This
variation equals plus or minus one standard deviation, which encompasses
68% of the population. The SpHb accuracy has not been validated with
motion or low perfusion.
7. The following substances may interfere with pulse CO-oximetry
measurements:
• Elevated levels of methaemoglobin (MetHb) may lead to inaccurate
SpO
2
and SpCO measurements.
• Elevated levels of carboxyhaemoglobin (COHb) may lead to inaccurate
SpO
2
and SpCO measurements.
• Very low arterial oxygen saturation (SpO
2
) levels may lead to inaccurate
SpCO and SpMet measurements.
• Severe anemia may cause erroneous SpO
2
measurements.
• Dyes or any substance containing dyes that change usual blood
pigmentation may cause erroneous readings.
• Elevated levels of total bilirubin may lead to inaccurate SpO
2
, SpMet,
SpCO, and SpHb measurements.
F.12 Basics of pulse oximetry
Nearly the full amount of the oxygen transported from the
lungs to the organs in the human body is present in a bound
form in the arterial blood. An iron containing protein called
haemoglobin is binding the oxygen molecules (4 binding sites
per each haemoglobin molecule). This form of the haemoglo-
bin is called oxyhaemoglobin, as opposed to deoxyhaemoglo-
bin, the form not binding oxygen.
Oxygen saturation is defined as the percentage of oxygen
binding sites occupied by oxygen. SpO
2
is an approximation of
the oxygen saturation, and it can be measured by a pulse oxi-
meter in the peripheral blood. It is defined as the ratio of oxy-
haemoglobin to the total concentration of haemoglobin
present in the blood.
SpO
2
= HbO
2
/(HbO
2
+Hb)
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