Appendix
Principle of flow measurement
The inspiratory and expiratory flow both stream through
the flow sensor positioned at the patient connection of
the breathing valve. The flow generates a pressure drop
in the sensor which is measured via two pressure
measuring hoses in Oxylog 2000. The pressure drop is
proportional to the flow.
The expiratory minute volume is calculated from the
measured expiratory flow and indicated.
The inspiratory volume supplied is calculated from the
measured inspiratory flow and then compared with the
expiratory volume to calculate the leakage, which is then
displayed.
The inspiratory flow measurement is also used to
synchronize the mandatory strokes in SIMV ventilation
mode.
Pressure effect of tidal volume on operation
of Air Mix
The air and oxygen are mixed by an injector which
additionally takes in air to produce an air/oxygen mixture
containing approx. 60 vol.% O2 (Air Mix).
For physical reasons, the suction performance of the
injector decreases as the back-pressure increases.
At high airway pressures, the set tidal volume VT may be
reduced and the O2 concentration increased when using
the Air Mix function.
At airway pressures between 20 and 30 mbar, the set
tidal volume is the same as the applied tidal volume VT.
The O2 concentration is around 60 vol.% O2. The set
tidal volume VT must be increased accordingly with the
aid of the measured minute volume at higher airway
pressures.
Appendix
Principle of flow measurement
Pressure effect of tidal volume on operation of Air Mix
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