7-11
7.3.3 Measurement Limitations
Measurement accuracy may be compromised due to:
Leakage or internal leakage of the sample gas
Mechanical shock
Cyclic pressure which is greater than 10 kPa (100 cmH
2
O)
Other interference source (if available)
Measurement accuracy may be affected by the breath rate and I/E ratio as follow:
EtCO
2
is within specification for breath rate ≤ 60 bpm and I/E ratio ≤ 1:1;
EtCO
2
is within specification for breath rate ≤ 30 bpm and I/E ratio ≤ 2:1.
Measurement accuracy is unspecified for breath rate larger than 60 bpm.
7.3.4 Zero the Sensor
Zeroing the sensor aims to eliminate the effect of baseline drift on the readings during the
measurement, so as to ensure measurement accuracy.
For mainstream CO
2
module, zero the sensor when:
1. The adapter is replaced.
2. The sensor is re-connected to the module.
3. The message [CO
2
Zero Required] is displayed. In this case, check the airway adapter
for blockage. If a blockage is detected, clear or replace the adapter.
To zero the sensor, do as follows:
1. Connect the sensor to the CO
2
module.
2. Select the [Setup] key→[Sensor]→[CO
2
] an set [Monitoring] to [ON].
3. After warm-up is finished, connect the sensor to a clean, dry airway adapter. The adapter
should be vented to the air and isolated from CO
2
sources, including ventilator, the
patient’s breathing and your own breathing.
4. Select the [Setup] key→[Calibrate]→[Zero]. Select the [Start] button corresponding
to CO
2
zeroing on the right side of the screen, and the screen displays [CO
2
Zeroing].
5. A typical zeroing takes about 15 to 20 seconds. This message disappears after zeroing is
completed.
WARNING
Before zeroing the sensor during the measurement, disconnect the sensor from the
breathing system first.
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