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Monitoring tcGas
The tcGas module measures the partial pressure of the oxygen and carbon dioxide that diffuses through the skin, thereby providing a measure of these gases in the capillary blood.
The monitor’s settings for altitude and barometric pressure influence the measurement. The tcpO2/ tcpCO2 measurement is valid for an infant patient not under gas anesthesia. Anesthetic agents, such as halothane, can cause incorrect or drifting readings.
Transcutaneous measurements cannot replace arterial blood gas monitoring. However, you can use transcutaneous monitoring to reduce the frequency of arterial sampling. The values at tissue level will not be the same as those measured arterially because the measurement is transcutaneous. They correlate with (track closely) the arterial values. For example, a drop in transcutaneous values usually indicates a corresponding drop in arterial values.
Transcutaneous values will not always correlate with blood samples taken from the capillary blood of the heel (heelsticks or astrups).
Identifying tcGas Module Components
1 press to enter Setup tcGas menu |
tcGas |
2 press to start calibration |
M1018A |
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3 calibration chamber |
1 |
4 transducer connector |
O2/CO2 CAL |
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2 |
80 x 70 |
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3 |
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4 |
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16 Monitoring tcGas |
Setting the tcGas Sensor Temperature |
Setting the tcGas Sensor Temperature
1 In the Setup tcGas menu, select Transducer Temp.
2Choose a temperature value appropriate for your patient’s age, weight and physical condition in accordance with your hospital policy.
Usually, a higher transducer temperature gives a better correlation and a quicker response time. However, higher temperatures also increase the risk of skin burns. Most physicians prefer a temperature between 42°C (107° F) and 44°C (111° F), and a site time of four hours or less. Usually, the higher the transducer temperature, the less the site time should be. Whenever you change the temperature setting, the monitor forces you to make a new calibration.
Using the tcGas Site Timer
Availability and behavior of the site timer depend on your monitor’s configuration.
WARNING Prolonged continuous monitoring may increase the risk of undesirable changes in skin characteristics, such as irritation, reddening, blistering or burns. If the site timer is disabled, the transducer will heat indefinitely while on a patient. Change the site regularly, in accordance with medical procedures in your hospital.
Setting the tcGas Site Timer
The site timer helps reduce the risk of skin burn by ensuring that the transducer is used at one site for no longer than a predefined period. It reminds you when this period expires.
1 In the Setup tcGas menu, select Site Time.
2Choose the time you want the transducer to remain on the measurement site. The optimum time depends on the transducer temperature and your patient’s skin sensitivity.
The site timer starts automatically when you remove the calibrated transducer from the calibration chamber. If you return the transducer to the chamber and then remove it again, the site time continues to count down the remaining time; it does not start a new time period. The time remaining before the site timer expires appears in the status line which is visible as long as the Setup tcGas menu is open. When the time expires, the monitor sounds a tone and a displays a change site INOP. The monitor either switches off the transducer heating or continues monitoring, depending on its configuration. Although you can reuse the transducer for up to two hours after the heating is switched off, without making a new calibration, you are recommended to recalibrate before applying it to a patient. After two hours without heat, you must recalibrate.
During the initial few minutes of use, the monitor eliminates false alarms by temporarily suppressing tcGas alarms. It displays the “STABILIZING” INOP. After you apply the transducer to the skin, the instrument reading slowly assumes a steady value. The reading stabilizes when the measurement site is warm and local hyperemization is complete. This takes 10 to 20 minutes for the tcpO2 reading and three to seven minutes for tcpCO2.
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Setting the tcGas Barometric Pressure |
16 Monitoring tcGas |
Restarting the tcGas SiteTimer
To restart the site timer without recalibration (for example, after the site time has elapsed):
1 In the Setup tcGas menu, select Site Time.
2 Enter and confirm your desired time.
Disabling the tcGas Site Timer
Depending on your monitor’s configuration, you might be able to disable the site timer. Remember, this means that the transducer heats indefinitely while on a patient.
1 In Setup tcGas menu, select Site Timer and switch this to Disabled.
2 Select the Confirm popup key.
Setting the tcGas Barometric Pressure
Altitude and barometric pressure affect tcGas values. The monitor derives barometric pressure from its altitude setting. If you want to set the true barometric pressure you must do this before starting a calibration - changes after calibration do not influence tcGas values. The monitor remembers this pressure setting until you enter a new one.
1 In the Setup tcGas menu, select AmbientPress.
2Enter the current barometric pressure reading indicated by your barometer.
3Select the Confirm popup key.
Remembraning the tcGas Transducer
CAUTION The tcGas transducer is thin and flexible. You must treat it with care. Avoid kinking, bending or pulling the cable.
Remembrane the transducer if the electrolyte in your transducer has dried out or:
•if the transducer is new
•if you are using the transducer with a new patient
•if the membranes are damaged (scratched or wrinkled)
•after five days of continued use or 28 days of storage.
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