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Description
Oxygen Ratio Control – S-ORC
Oxygen Ratio Control – S-ORC
To prevent the setting of hypoxic gas mixtures,
Cicero EM has an O
ratio control system (SORC =
2
Sensitive Oxygen Ratio Control).
The O
and N
O flows build up control pressures for a
2
2
switching diaphragm in a flow restrictor. The pressure
ratio on the switching diaphragm controls the N
N
O is disabled when the O
2
200 mL/min; it is slowly re-enabled as the value rises.
When the O
flow reaches approx. 300 mL/min, the
2
proportion of N
O contained in the fresh gas can be
2
freely varied between 0 and 75 %.
Since the maximum delivery capacity of both flow tubes
is limited (but at least 9 L/min, depending on the pressure
in the gas supply), the minimum O
increases above approx. 2500 mL/min until both flow
tubes are completely open and the mixing ratio of
O
: N
O is approx. 50 : 50.
2
2
The principle is illustrated in the diagram:
The curves are displaced when anaesthetic vapours
(by up to 18% in the case of desflurane!) are delivered!
Concentration ratio
O
/ N
O
2
2
100 / 0
90 / 10
80 / 20
70 / 30
60 / 40
50 / 50
40 / 60
30 / 70
20 / 80
10 / 90
0 / 100
0
250
182
O flow.
2
flow drops below approx.
2
concentration
2
O
/N
O ratios which can be set with the
2
2
control valves on the bank of measuring tubes
Minimum O
2
500
750
O
2
in the bank of
measuring tubes
Flow restrictors
ORC
O
2
Control valves
concentration
1 000
2 250
N
O
2
Flow tubes
N
2
shutoff
valve
Control
diaphragms
N
O
2
O
100 / 0
90 / 10
80 / 20
70 / 30
60 / 40
50 / 50
40 / 60
30 / 70
20 / 80
10 / 90
0 / 100
3 000
O
-Flow [mL/min]
2
O-
/ N
O
2
2
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