Troubleshooting
83
11. Oxygen saturation measurement does not correlate
with the value calculated from a blood gas
determination.
• The SpO2
calculation may not have correctly adjusted
for the effects of pH, temperature, PaCO2, or 2,3-DPG.
Check whether calculations have been corrected
appropriately for relevant variables. (See the
Principles of Operation section for more information.)
In general, calculated saturation values are not as
reliable as direct laboratory hemoximeter
measurements.
• Accuracy can be affected by incorrect sensor
application or use, significant levels of dysfunctional
hemoglobins, intravascular dyes, bright light,
excessive patient movement, venous pulsations,
electrosurgical interference, and placement of a sensor
on an extremity that has a blood pressure cuff, arterial
catheter, or intravascular line. Observe all
instructions, warnings, and cautions in this manual
and in the sensor Directions for Use.
12. Oxygen saturation does not correlate with
laboratory hemoximeter.
• Fractional measurements may not have been converted
to functional measurements before the comparison was
made. The N-200, as well as other two-wavelength
oximeters, measure functional saturation. Multi-
wavelength oximeters, such as the Instrumentation
Laboratory282 CO -Oximeter and Corning
CO-oximeters, measure fractional saturation.
Fractional measurements must be converted to
functional measurements for comparison. Refer to the
equation for this conversion in the Principles of
Operation section.
• Close correlation requires simultaneous blood
sampling and pulse oximeter measurements from the
same arterial supply.
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