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17 Monitoring SvO
2
Performing In-Vivo Calibration
206
Performing In-Vivo Calibration
Perform an in-vivo calibration:
• if you place the catheter in a patient without performing a pre-insertion calibration.
• if the catheter was disconnected from the optical module.
• when the catheter has been in the patient for 24 hours.
• if any significant change in light intensity occurs that the monitor cannot correct automatically.
Setting Up the In-Vivo Calibration
Check for:
• proper positioning of the catheter in the patient.
• relatively stable oxygen saturation in patient.
• that the Sv
O
2
light intensity indicator covers at least two divisions above the midpoint.
Making the In-Vivo Calibration
1 Be prepared to draw a blood sample from the patient.
2 In the Setup SvO2 menu, select Start In-VivoCal.
3 To clear the distal lumen, draw off and discard at least 2 ml of blood before taking the sample.
4 Draw a blood sample from the distal port of the catheter and flush the line according to standard
hospital practice.
5 Obtain laboratory analysis of the sample using direct measurements.
6 Compare the results with the stored calibration value displayed in the Setup SvO2 menu. If the
difference is less, or equal, to 4%, you can skip the next step.
7 If there is a difference of more than 4% between the stored value and the laboratory value, select
CalibrationValue to adjust the stored value. Selecting Recall PreviousC recalls the
previously stored calibration value.
8 Complete the calibration by selecting Store In-VivoCal (even if you did not adjust the
calibration value). This updates the data stored in the optical module.
Calculating Oxygen Extraction
Oxygen extraction is the difference between the measured SpO
2
and SvO
2
values. If you are
monitoring SpO
2
and SvO
2
, the monitor can calculate this value and display it as a numeric.
♦ To switch oxygen extraction calculation on or off, in the Setup Sp-vO2 menu, select Sp-vO2
and toggle between On and Off.
♦ If more than one SpO
2
value is available, you must choose which value is used in the calculation.
In the Setup Sp-vO2 menu, select SpO2 Source and select the required source.
If one of the calculation sources becomes unavailable, the monitor displays the INOP
Sp-vO2 CHK SOURCES for one minute. After this time, the calculation automatically switches off.
If the missing source becomes available again, the calculation automatically switches on again.