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Description
Ventilation Modes
APRV
Airway Pressure Release Ventilation
Spontaneous breathing under continuous positive airway
pressure with brief pressure release. This ventilation
mode is suitable for patients with a poor gas exchange.
The patient breathes spontaneously at a high pressure
level P
for an adjustable length of time T
high
short expiration times T
, Evita 4 switches to a low
low
pressure level P
. The normal lung areas are emptied,
low
but the "slow" lung areas only change volume to a lesser
extent.*
In this way, the ventilation/perfusion ratio can be
improved for patients with a poor gas exchange.
The steepness of the increase from the lower pressure
level to the upper pressure level is controlled by the
setting
. The effective time for the increase in pressure
cannot become greater than the set time T
MMV
Mandatory Minute Ventilation
In contrast to SIMV, the MMV ventilation mode gives
mandatory breathing 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 V
and frequency f, and results from
T
the product V
x f.
T
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 V
If there is no spontaneous breathing at all, the mandatory
strokes are applied at the set frequency f.
____________
* Bibliography (6), (7), (8), (9), page 182
168
Paw
P
high
. For very
high
.
high
Paw
T
Flow
V
are applied.
T
MV
set
MV
mandatory MV
no spontaneous
breathing
T
high
T
low
ASB
pressure support
short
rise time
Pmax
PEEP
trigger phase
insp
1
f
T
Insp. Flow
beginning spontaneous
breathing
P
low
t
long
rise time
t
t
spontaneously
breathed MV
t
sufficient spontaneous
breathing
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