A set inspiration time Tinsp shorter than the lung filling
time can be recognised from the flow curve: the flow at
the end of the inspiration time has not dropped to zero.
Here, it must be decided whether the current condition of
the patient permits prolongation of the inspiration time in
order to reduce the peak pressure even further.
This effect can also be caused during ventilation, e.g.
due to a build-up of secretion. In this situation, the
pressure is limited by the alarm limit »Paw W«. The
pressure rise stops 5 mbar below the alarm limit
»Paw W«, and the alarm »Volume not constant« is only
given when the set tidal volume VT is not longer applied.
The start of mandatory inspiration can be synchronised
with the patient's own efforts with the aid of the variable
Flowtrigger. Only in IPPV mode can Flowtrigger be fully
switched off (IPPV Assist -> IPPV).
The steepness of the pressure rise from the PEEP level
to the inspiration level can be even more closely adapted
to the needs of the patient in SIMV and MMV modes by
means of the pressure rise time » «.
Start-up procedure with AutoFlow
On switching on the AutoFlow
function, Evita 4 applies
the set tidal volume VT through a volume-controlled
ventilation stroke with minimum inspiration flow and
subsequent inspiratory pause.
The plateau pressure Pplat calculated for this ventilation
stroke serves as start-up inspiration pressure for the
AutoFlow
function.
162
Description
Ventilation Modes
Paw
Paw >
Flow
ohne Spontanatmung mit Spontanatmung
V
T
PEEP
Tinsp Te
1
f
t
t
Pinsp = f (VT,C)
without spontaneous breathing with spontaneous breathing