Page 136 of 292
14.1.10 Breath Detection
The breath detection threshold needs to be set in all patient interactive modes.
Setting the breath detection threshold at its most sensitive level (0.2ml) may allow
the ventilator to interpret background noise in the patient circuit as patient
breathing, resulting in auto-triggering.
When the ventilator is used with a flow sensor the ventilator monitors gas flow to
detect the patient breath.
When the ventilator is used without a flow sensor the ventilator monitors
pressure change to detect the patient breath and in this case the user will have to
set the Breath Trigger Sensitivity.
14.1.11 Max Ti in PSV
The user needs to be made aware that in PSV mode the inspiratory time
parameter control is labeled Max Ti (Maximum inspiratory time). This is because
the termination sensitivity control (stop support at %) can terminate the breath
before the set inspiratory time is reached. The actual inspiratory time is displayed
in the lung mechanics and measurement panel as Ti meas.
14.1.12 TTV (Targeted Tidal Volume)
14.1.12.1 Max Ti
When TTV is set to ON in CPAP, CMV, PTV and SIMV the Ti control changes to
Max Ti. This is because when the set volume has been delivered the breath is
terminated. This termination of the breath can be before the set inspiratory time is
reached. The actual inspiratory time is displayed in the lung mechanics and
measurement panel as Ti meas.
Note: The user can increase the measured inspiratory time in TTV by
changing the waveshape, i.e. decreasing the inspiratory rise time.
Decreasing the rise time has the effect of slowing the achievement of the
set volume thus increasing the measured inspiratory time.
14.1.12.2 Max PIP
When enabling TTV the PIP control changes to the Max PIP. For a mode with
TTV ON the PIP can be greater than that required in the same mode with TTV
OFF. When switching from a mode with TTV ON to a mode that does not support
TTV (HFO & HFO+CMV) or to a mode where the user turns OFF TTV the
ventilator defaults the PIP level to 5 mbar above the set PEEP level, irrespective
of what the user has set. The User will then have to reset the PIP to the required
level. This prevents the maximum PIP being delivered.
14.1.12.3 Tidal Vol. Parameter Reading
The flow sensor has a stated percentage reading error of 8% (maximum).See
“Measurement” on page 266. The user must note that the set tidal volume and
the measured tidal volume can differ. Also the cleanliness of the sensor
(secretions on the wires) and the age of the sensor, can also affect the accuracy
of the reading.
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