Aeonmed Aeon8800A - Page 162

9.Technical data
153
Where:
EtCO
2
= EtCO
2
value sent from ISA [vol %]
Pamb = Ambient pressure sent from ISA [kPa]
3.8 = Typical partial pressure of water vapor condensed between patient circuit and ISA [kPa]
EtCO
2
(BTPS) = EtCO
2
gas concentration at BTPS [vol%]
O
2
is assumed to be room Air calibrated at a humidity level of 0.7 vol% H
2
O.
Spectral broadening
The presence of oxygen and nitrous oxide can cause some interference in the CO
2
measurement.
This is known as spectral broadening.
Nitrous oxide, N
2
O:
N
2
O compensation is not included in the system. Therefore, for the N
2
O broadening effect on CO
2
measurement accuracy, please refer to the below table.
Table 9-17 N
2
O concentration in gas mix
N
2
O concentration in gas mix
Effect on gas reading
Displayed value if true
concentration is 5.0 vol% CO
2
0 vol%
0% relative
5.3 vol%
30 vol%
5.17% relative
5.3 vol%
60 vol%
10.34 relative
5.5 vol%
82 vol%
14.14% relative
5.7 vol%
Oxygen, O
2
:
ISA sidestream analyzers capable of O
2
measurements automatically compensates for spectral
broadening caused by oxygen.
For most applications, sufficient accuracy in CO
2
measurement will be achieved by dividing the
oxygen concentration into three ranges: “high”, “medium” and “low”. By using these ranges, along
with the Set O
2
values in the table below, the maximal relative CO
2
error will be limited to 1.2%.
Table 9-18 O
2
range
O
2
range
Set O
2
parameter
0-30 vol%
21
30-70 vol%
50
70-100 vol%
85
Gas measurement units
Gas concentration is reported in units of volume percent. The concentration is defined as: