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3.6 SIMV
Synchronised Intermittent Mandatory
Ventilation
The frequency of mandatory breaths is determined
by the BPM control. When a mandatory breath is
due an assist window opens and waits for a
patient's inspiratory effort. When this occurs the
ventilator delivers a synchronised breath (SIMV
breaths). Once the breath has been delivered the
assist window closes until the next set breath is due.
If the ventilator does not see a patient's attempt to
breathe before the end of the defined time window
then a mandatory breath is delivered. The
mandatory breath point is the Time Window minus
the Inspiratory Time.
User sets the following:-
• BPM
• Apnoea alarm time (Only if backup breath rate is
9 breaths per minute or lower)*
• Positive End Expired Pressure (PEEP)
• Peak Inspiratory Pressure (PIP)
• Inspiratory Time (Ti)
• O
2
%
• Flow breath detection threshold (Trigger
Sensitivity) – The patient effort required for the
ventilator to recognise the breath.
• High and low pressure alarm thresholds
• Tidal volume, high and low alarm thresholds
• Minute volume, high and low alarm threshold
3.6.1 SIMV with PSV
SIMV with PSV allows the user to select the
termination sensitivity and pressure support level on
non SIMV breaths. Once a mechanical breath is
delivered to the patient, the flow to the infant rapidly
peaks and then decelerates to the termination
threshold, inspiration ends and expiration can begin.
The following parameters must be selected: PEEP,
PIP, Ti, Breath detection level, Termination
sensitivity level, Backup BPM, Apnoea delay time,
O
2
%.
SIMV with PSV produces time cycled, pressure
limited breaths that are delivered at a set BPM rate.
Any additional patient breath attempts are pressure
supported (Flow cycled, pressure limited).
User sets the following:-
• The flow termination sensitivity
• Percentage pressure support, expressed as %
∆P (PIP minus PEEP)
3.6.2 SIMV with TTV
plus
(Targeted Tidal Volume)
This is as for basic SIMV (with or without Pressure
Support) with Apnoea Support, where the
inspiratory pressure shall be controlled by the
ventilator to achieve the user set Vte (for assisted
breaths).
The User sets the following:-
• Enables Targeted Tidal Volume (Vte (TTV)) and
selects volume to be delivered
• Max PIP
*Note: SIMV will continue to function as
stated, but with breath rate of 10 and above,
the Apnoea alarms are de-activated. Backup
rate of 10 BPM and above are deemed
sufficient to support the patient.
Assist windows
Time windows
60
BPM
Time window =
Inspiratory time
Mandatory breath point
Note: The ventilator does not apply
termination sensitivity to SIMV breaths. All
patient triggered, pressure supported breaths
are flow terminated unless the user sets the
stop support percentage value to OFF.
Supported
SIMV breath
SIMV breath
breath
Un-supported
patient breath
below trigger
threshold
triggered
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