Flow Measurement,
Principle of Operation
The flow sensor is located at the patient connector end
of the patient valve and both inspiratory and expiratory
flow pass through it.
The flow creates a pressure drop in the sensor which is
measured inside the Oxylog 2000 via two pressure
sensing lines. The pressure drop is proportional to flow.
Expiratory minute ventilation is calculated from the
measurement of expiratory flow and displayed.
Applied inspiratory volume is calculated from the
measurement of inspiratory flow, it is then compared to
expiratory volume and leakage is calculated and dis-
played.
Furthermore, measurement of inspiratory flow is used to
synchronize mandatory ventilator breaths in SIMV mode.
Pressure Dependent Tidal Volume
With Air Mix
Mixing of air and oxygen is performed using an injector,
which draws additional air and creates a mixture of oxy-
gen and air with a concentration of approximately 60%.
Due to the physics involved, the performance of an
injector decreases with increasing back pressure.
With high airway pressures and »Air Mix« on, the set tidal
volume VT may be reduced and the resulting O2 concen-
tration may be increased.
Set and actually applied tidal volume VT match at an
airway pressure of 20 cmH2O, the O2 concentration is
then approximately 60%. At higher airway pressures, set
tidal volume VT needs to be increased using measured
minute ventilation as guidance.
Theory of Operation
Flow Measurement, Principle of Operation
Pressure Dependent Tidal Volume With Air Mix
Operating Instructions Oxylog 2000, SW 3.n
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