Covidien Nellcor - Unique Technologies; Functional Versus Fractional Saturation

Unique Technologies
Operator’s Manual 83
These capabilities are beyond the scope of known bench top testers. SpO2
measurement accuracy can only be evaluated in vivo by comparing monitoring
system readings with values traceable to SaO2 measurements obtained from
simultaneously sampled arterial blood using a laboratory CO-oximeter.
Many functional testers and patient simulators have been designed to inter-
face with the monitoring system's expected calibration curves and may be suit-
able for use with monitoring systems and/or sensors. Not all such devices,
however, are adapted for use with the OxiMax™ digital calibration system.
While this will not affect use of the simulator for verifying system functionality,
displayed SpO
2 measurement values may differ from the setting of the test
device. For a properly functioning monitoring system, this difference will be
reproducible over time and from monitoring system to monitoring system
within the performance specifications of the test device.
10.5 Unique Technologies
10.5.1 Functional versus Fractional Saturation
This monitoring system measures functional saturation where oxygenated
hemoglobin is 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 where oxygenated hemoglobin
is expressed as a percentage of all measured hemoglobin, including measured
dysfunctional hemoglobins. To compare functional saturation measurements
to those from a monitoring system that measures fractional saturation, frac-
tional measurements must be converted using the listed equation.
functional saturation %carboxyhemoglobin
fractional saturation %methemoglobin


100 +–
---------------------------------
100=



