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14.1.14 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.
14.1.15 Targeted Tidal Volume, Vte (TTV)
14.1.15.1 Ti
When TTV
plus
is set to ON in CPAP, CMV, PTV and
SIMV, if the inspiratory volume exceeds a safety
limit, the breath is terminated, to prevent over-
distension of the lung. This will result in a lower
measured Ti than set. The actual inspiratory time is
displayed in the lung mechanics and measurement
panel as Ti meas.
14.1.16 Max Ti in PSV
In PSV mode the Ti parameter is marked Max Ti
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.
14.1.16.1 Max PIP
When TTV
plus
is set to ON the PIP control changes
to the Max PIP. The amount of PIP is taken from the
measured value which is required to maintain the
measured volume.
When switching from a mode with TTV
plus
set to ON
to a mode that does not support TTV
plus
,or when the
user turns OFF TTV
plus
the ventilator sets the PIP
level to the last used PIP level required to maintain
the appropriate volume from the MAX PIP control or
with a minimum of 5 mbar above the set PEEP. The
user should ensure the PIP is set correctly and
adjust if required.
14.1.16.2 Continuing without flow with TTV
plus
ON
When the user disconnects the flow sensor when
ventilating in a mode with TTV
plus
ON, the ventilator
sets the PIP level to the last used PIP level form the
MAX PIP control (Note: This is not the set MAX PIP)
or with a minimum of 5 mbar above the set PEEP.
The user should ensure the PIP is set correctly and
adjust if required.
14.1.16.3 Limitations on PIP (Max PIP) during
TTV
plus
operation
During TTV
plus
operation the device automatically
adjusts the PIP in order to achieve the targeted Vte
value. Upward adjustment of PIP during TTV
plus
shall be limited by the Max PIP setting. Downward
adjustments of PIP during TTV
plus
shall be limited to
a minimum of 3mbar above the PEEP setting.
14.1.16.4 Fluctuation of measured Vte
The Vte now displayed will either be for mechanical
(large) or spontaneous (small) breaths (See section
2.13 on page 12 for the table describing large and
small breath types). The Vte value in the lung
mechanics panel will fluctuate between the large
and small breath measurements.
The measured Vte displayed in the Vte (TTV)
parameter control is for large breaths only.
Caution. The user should set the MAX PIP
close to measured PIP (4 to 5 mbar above
measured PIP or as per clinical
recommendation). If the flow sensor is
removed from the circuit (for suctioning or re-
calibration), the ventilator senses that the Vte
has dropped below the set target level, it then
starts to increase the pressure within MAX
PIP to try and achieve the target volume (the
“Clean Flow Sensor” alarm with the “Reset
Contamination Alarm” button may be
triggered).
Note: For frequent fluctuation of the Vte in the
lung mechanics panel, prior changing the
ventilation parameters check the following:
a. The trigger sensitivity (Breath detection
threshold)
b. Examine the waveforms (Pressure, Flow &
Tidal Volume).
c. Check the Minute Volume.
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