Measuring ventilation ratios
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IMT Analytics AG
If you are setting a trigger for the first time, it is important to know the characteristic of
the signal that will be used for the trigger (flow or pressure). It is therefore advisable to
analyse that characteristic with the FlowLab software first. Graphically it is then very
easy to decide where the triggers should be placed.
In the following we will now show a few examples that also point to potential prob-
lems.
8.5.1
Flow curve downstream of the Y-piece
This example shows a flow curve downstream of the Y-piece. The standard triggers
(> 3 L/min / < -3 L/min) can be used in this case without any problems.
In such a situation it is important to ensure that the trigger is signifi-
cantly above the noise of the baseline or else false triggering can be
caused.
8.5.2
Flow curve upstream of the Y-piece
False triggering
This graph shows the flow curve in the inspiratory channel upstream of the Y-piece.
The first two circles indicate the triggers that should be used in this case.
The illustration above shows that at this measuring point after inspiration a small false
signal is still visible which was generated by switching over the valves. This leads to
false triggering!
Here the flow must not be used as a trigger! The pressure curve must
be used instead (
8.5.3 Pressure curve upstream of the Y-piece
).
8.5 Finding the correct
trigger values