16 Monitoring tcGas
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Apply the transducer as soon as possible after you see the message indicating that calibration is
complete. If you wait longer than 30 minutes, the heat supply to the transducer switches off to
prevent the electrolyte from drying out and a new calibration is necessary.
Optimize the measurement by selecting a site with high capillary density and blood flow, thin
epidermis and no cardiovascular disorders. Most physicians use the abdomen, chest and back.
WARNING
You must either remove the transducer before defibrillating, or remembrane and calibrate the
transducer after defibrillating.
CAUTION
To avoid transducer damage, remove it from the patient during high frequency surgical procedures.
Selecting the tcGas HeatPowerDisplay Mode
The heat power display gives an indication of the skin's perfusion below the transducer and of the
transducer's contact with the skin. If the transducer loses contact, the heat power value drops
significantly. When perfusion is poor you need less heat power to maintain the transducer temperature.
•In the
Setup tcGas menu, select HeatPowerDisplay and then Relative or Absolute. Choose
Relative when the skin temperature is stable (the <tcGas Label> Stabilizing INOP disappears).
This indicates subsequent changes in the relative heat power (and therefore changes in perfusion
or transducer contact) since the last zeroing.
Finishing tcGas Monitoring
Replace the transducer in the calibration chamber.
When changing the application site after a measuring period, some users leave the fixation rings in
position to allow them to quickly move the transducer from site to site. Always unscrew the transducer
from the fixation ring before removing the fixation ring from the skin.
Zeroing the tcGas Relative Heat Power
When you start a calibration, the HeatPowerDisplay is set to Absolute. When you switch to Relative,
it automatically zeros. Zero again if you change application site.
TcGas Corrections
Transcutaneous pCO
2
values tend to be higher than arterial values due to the metabolic processes of
the skin and the effect of heating on the blood under the transducer. Depending on your monitor's
configuration, one or both of these corrections may automatically apply.
Temperature Correction for tcpCO2
The transducer temperature causes an increase in partial CO
2
pressure. Your monitor may be
configured to correct this.
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