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P
V
V
V
< V
TI
Figure 4.24: Mode PS.SV (PS), pressure increased to reach V
Expiratory phase
The device cycles into the expiratory phase:
•
When the expiratory trigger setting is reached. The setting may be:
•
based on the peak flow drop (Scenario No. 1);
•
an automatic setting based on the intersection of the flow curve with the 3s line
(Scenario No. 2).
•
If the set pressure of 2cmH
have initiated active exhalation (Scenario No. 3).
•
When the maximum inspiratory time set by the user is reached (Scenario No. 4), if none of
the above conditions are met. This scenario can occur if there are leaks in the circuit, or if the
flow doesn't decrease sufficiently to reach the expiratory trigger setting.
Pressure parameter
P
V
Scenario No. 1: Peak
flow drop of XX%
Figure 4.25: Expiratory phases in PS.SV (PS) mode.
Note: The set PS level is added to the PEEP level.
NOT013189-6
PS
PEEP
V
< V
TS
TI
TS
O is exceeded during the decreasing flow stage, the patient may
2
Scenario No. 2:
Intersection of the
flow curve with the
3 second line
3 seconds
PS max = PS + PEEP + 5 hPa +20% (PS + PEEP)
PS + PS max/2
PS
PEEP
V
= V
TI
TS
.
TS
Scenario No. 3: Pressure
exceeded by > 2 cmH2O
Scenario No. 4: Ti Max
value reached
t
t
t
t
t
Ventilation
57/170
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