Functional Versus Fractional Saturation; Measured Versus Calculated Saturation - Covidien Nellcor OxiMax N-600x Operator's Manual

Functional versus Fractional Saturation

Measured versus Calculated Saturation

N-600x Operator's Manual
This pulse oximeter measures functional saturation – oxygenated
hemoglobin expressed as a percentage of the hemoglobin that
can transport oxygen. It does not detect significant amounts of
dysfunctional hemoglobin, such as carboxyhemoglobin or
methemoglobin. In contrast, hemoximeters such as the IL482
report fractional saturation – oxygenated hemoglobin expressed
as a percentage of all measured hemoglobin, including measured
dysfunctional hemoglobins. To compare functional saturation
measurements to those from an instrument that measures
fractional saturation, fractional measurements must be converted
as follows:
When saturation is calculated from a blood gas partial pressure of
oxygen (PO ), the calculated value may differ from the SpO
2
measurement of a pulse oximeter. This usually occurs because the
calculated saturation was not properly corrected for the effects of
variables that shift the relationship between PO
Principles of Operation
2
and pH,
2
163