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Description
Ventilation Modes
Sigh (intermittent PEEP)
"Sigh", in the form of intermittent PEEP, is operative in IPPV,
IPPV
Assist and ILV modes.
The purpose of the 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, this
form of sigh only marginally improves the filling of the "slow"
alveoli.
In Evita 2 dura, 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 peaks of pressure during
the sigh phase can be limited by the pressure limit Pmax
without impairing the sigh function.
During the sigh phase, the "Volume not constant" alarm is
disabled.
008
Paw
Sigh phase
Pmax
interm.
PEEP
PEEP
t
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