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Sigh
"Sigh« is operative in the form of intermittent PEEP in
IPPV, IPPV Assist and ILV.
The purpose of expiratory sigh during ventilation is to
open collapsed areas of the lung, or to keep open "slow"
areas of the lung.
Since atelectatic alveoli have a longer time constant –
also caused by obstructed bronchioles – increased
airway pressure maintained over a longer period is
required to open them.
In many cases, the sigh function is achieved by
increasing the ventilation stroke; however, due to the
short time available, the filling of the »slow« alveoli is only
marginally improved.
In Evita 4, the sigh operates during expiration with an
intermittent PEEP for two ventilation strokes every
3 minutes.
The average airway pressure is higher, and a longer filling
time is normally available.
To avoid overinflation of the lung, the pressure peaks
during the sigh phase can be limited by pressure
limitation, Pmax, without impairing the sigh function.
During the sigh phase, the "Volume not constant" alarm
is disabled.
Paw
Pmax
interm.
PEEP
PEEP
Description
Ventilation Modes
Sigh phase
t
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