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SIMV
Synchronized Intermittent Mandatory
Ventilation
Mixture of mechanical ventilation and spontaneous
breathing.
In SIMV mode, the patient can breathe spontaneously
at specified regular intervals. Between these intervals,
mandatory (i.e. automatically delivered) ventilation strokes
ensure a minimum degree of ventilation.
The mandatory ventilation strokes are the same as those
for IPPV ventilation. They are defined by the parameters
V
, IPPV frequency f
, T
T
IPPV
Each mandatory breath is followed by a pause in which
the patient can breathe spontaneously.
In order to prevent the next mandatory breath being
applied during the expiratory phase of spontaneous
breathing, a trigger function ensures that the mandatory
ventilation stroke is synchronized with the inspiratory
spontaneous breathing phase during an expectation
period.
The time between the end of each mandatory ventilation
stroke and the beginning of the next is subdivided into a
spontaneous breathing time T
T
.
Trigger
Airway pressure over time:
Paw
Mandatory breath
Trigger
window (T
)
Trigger
T
:T
and T
.
I
E
IP
and a trigger time
Spont
Start of a new
mandatory breath
after triggering
Trigger window
T
Spont
T
Insp
Exsp
1
/
f
IPPV
1
/
f
IMV
Start of a new
mandatory breath
without triggering
Trigger window
T
T
Trigger
Spont
T
T
Insp
Exsp
1
/
f
IPPV
1
/
f
IMV
Descriptions
t
T
Trigger
∆T
SIMV
133
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