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17.2 Sidestream CO2 Module
NOTE
•
This section is only applicable to a monitor equipped with a sidestream CO2
module.
17.2.1 Principles of Operation
WARNING
•
The CO2 module should be protected against crash and vibration.
•
Inaccurate measurement may occur when the monitor is operating in an
environment of excessively high CO2 content (>0.5%).
The monitor adopts sidestream CO2 module. The measurement of this module is based on the
feature that the CO2 molecule absorbs infrared ray. The measurement procedure is as
follows :
send the CO2 to a measurement chamber inside the module through the airway system, and
then irradiate 4.26um infrared ray at one side of the chamber and use the sensor to measure
the attenuation degree of the received infrared ray at the other side. Since the attenuation
degree of the infrared ray is proportional to the concentration of CO2, the CO2 concentration
is calculated. The measured CO2 concentration is thereafter converted into the partial
pressure under the same temperature and pressure, and then displayed.
The relation between the partial pressure and the CO2 concentration is given below:
CO2 partial pressure (mmHg)=
CO2 concentration (%)×Pamp (ambient pressure, mmHg)/100
CO2 partial pressure (kPa)= CO2 partial pressure (mmHg)/7.5
17-2