Covidien Nellcor GR101704, Service Manual

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Theory of Operations
3-4 Service Manual
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.
3.6
Unique Technologies
3.6.1
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.
3.6.2
Measured versus Calculated Saturation
When calculating saturation from a blood gas partial pressure of oxygen (PO2),
the calculated value may differ from the SpO
2
measurement of a monitoring
system. This usually occurs when saturation calculations exclude corrections
for the effects of variables such as pH, temperature, the partial pressure of
carbon dioxide (PCO2), and 2,3-DPG, that shift the relationship between PO2
and SpO
2
.
functional saturation %carboxyhemoglobin
fractional saturation %methemoglobin


100
 
+
 
–
---------------------------------
100

=



