15-12
15.3 Oridion CO
2
Module
NOTE
z This section is applicable to a monitor equipped with the Oridion CO2 module
only.
z When the sample flow is lower than 42.5 ml/min, alarm message will be displayed,
and the CO
2
module will stop work.
15.3.1 Principles of Operation
WARNING
z The CO2 module should be protected against crash and vibration.
z This CO2 module is applicable to neonate, pediatric as well as adult patients.
z Inaccurate measurement may occur when the monitor is operating in an
environment of excessively high CO2 content (>0.5%).
The monitor adopts Oridion (microstream) CO
2
module. The measurement of this module is
based on the feature that the CO
2
molecule absorbs infrared ray. The measurement procedure is as
follows : send the CO
2
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 CO
2
, the CO
2
concentration is
calculated. The measured CO
2
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 CO
2
concentration is given below:
CO
2
partial pressure (mmHg)=
CO
2
concentration (%)×Pamp (ambient pressure, mmHg)/100
CO
2
partial pressure (kPa)= CO
2
partial pressure (mmHg)/7.5
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