EvitaXL

SIMV
Synchronised Intermittent Mandatory Ventilation
Combination of machine ventilation and spontaneous
breathing.
SIMV enables the patient to breathe spontaneously in regular
prescribed cycles, with the mechanical mandatory ventilation
strokes providing a minimum ventilation during the remaining
cycles. The minimum ventilation is controlled by the two set values
tidal volume (VT) and ventilation frequency (f) and is determined
from the product of VT x f.
The ventilation pattern results from the set values tidal
volume VT, insp. flow, frequency f and inspiration time Tinsp.
To prevent the mandatory ventilation stroke being applied during
spontaneous expiration, the Flowtrigger of the machine
ensures that the ventilation stroke is triggered in synchrony
with the patient's spontaneous inspiratory effort within a
"trigger window".
The "trigger window" is 5 seconds long in adult mode and
1.5 seconds long in paediatric mode. For expiration times
shorter than 5 seconds or 1.5 seconds, the "trigger window"
covers the entire expiration time.
Since the synchronisation of the mandatory ventilation stroke
reduces the effective SIMV time, which would result in an
undesirable increase in effective IMV frequency, EvitaXL prolongs
the subsequent breathing time by the missing time difference
∆T – thus preventing an increase in SIMV frequency.
The frequency parameter f remains constant. This parameter,
in combination with the tidal volume VT, sets the minimum ventilation.
If the inspiratory volume of the patient is considerable
at the beginning of the "trigger window", the machine reduces
the subsequent mandatory ventilation stroke by shortening the
time for the inspiratory flow phase and the inspiration time. In
this way, the tidal volume VT remains constant, and overinflation
of the lungs is avoided.
During the spontaneous breathing phases, the patient can be
assisted with pressure by ASB pressure support.
In the further weaning process, the frequency f on the ventilation
unit is further reduced, thereby prolonging the spontaneous
breathing time, until finally the required minute volume is
entirely covered by spontaneous breathing.
Ventilation Modes
SIMV
Instructions for Use EvitaXL 211
PAW
PEEP
trigger
window
mandatory
ventilation
Tinsp
spontaneous
breathing
spontaneous
breathing time
synchronised
mandatory
stroke
spontaneous breathing
time + T
set IMV time set IMV time
1
1
f
f
t
020