EvitaXL

Ventilation Modes
MMV
MMV
Mandatory Minute Volume Ventilation
In contrast to SIMV, the MMV ventilation mode gives mandatory
ventilation only if spontaneous breathing is not yet sufficient
and has fallen below a pre-selected minimum ventilation.
This minimum ventilation is controlled by the two set values
tidal volume VT and frequency f, and results from the
product VT x f.
Unlike SIMV, the mandatory strokes are not given regularly but
only in cases of insufficient ventilation.
The frequency of mandatory strokes is determined by the level
of spontaneous breathing:
if spontaneous breathing is sufficient, mandatory strokes are
not used. If spontaneous breathing is not sufficient, intermittent
mandatory strokes of the set tidal volume VT are applied.
If there is no spontaneous breathing at all, the mandatory
strokes are applied at the set frequency f.
EvitaXL continuously balances the difference between spontaneous
breathing and the set minimum ventilation. As soon as
the balance becomes negative, because spontaneous breathing
is no longer sufficient, EvitaXL applies a mandatory ventilation
stroke at the set tidal volume VT, so that the balance is
positive again.
Experience shows patients breathe very irregularly.
Phases of shallow breathing alternate with phases of tachypnoea
and large respiratory effort. In order to allow for these
individual fluctuations, the balancing process also takes
account of the extent by which the set minimum ventilation has
been exceeded.
This value is progressively reduced to zero by EvitaXL within
a maximum time of 7.5 seconds after apnoea.
In this way, the response time of EvitaXL is automatically
adapted to the preceding cycle of spontaneous breathing
before activating mandatory ventilation:
If this spontaneous breathing was close to the minimum ventilation,
EvitaXL responds rapidly within the cycle time (1/f).
However, if the patient's spontaneous breathing was much
higher than the set minimum ventilation, EvitaXL tolerates a
longer breathing pause. In extreme cases of sudden apnoea
after a phase of heavy spontaneous breathing, the response
time will be 7.5 seconds plus the trigger time, with a minimum
of one cycle time (1/f).
212 Instructions for Use EvitaXL
PAW
Flow
set
MV
MV
Tinsp
VT
PEEP
1
f
Insp. flow
mandatory MV
no spontaneous
breathing
Pmax
(configurable)
ASB pressure
support
short
rise time
trigger phase
beginning spontaneous
breathing
long
rise time
spontaneously
breathed MV
t
sufficient spontaneous
breathing
t
t
011
012