Siemens Drager medical Carina, Instructions For Use Manual, Page: 129 / 144

Instructions for Use Carina SW 3.n
129
Description
VC-SIMV
Volume Control – Synchronised Intermittent Man-
datory Ventilation
Hybrid form of mandatory ventilation and spontane-
ous breathing.
SIMV enables the patient to breathe spontaneously
in regular prescribed cycles, with the mechanical
mandatory ventilation strokes providing a minimum
ventilation during the remaining cycles.
This minimum ventilation is predetermined by the
two settings of tidal volume VT and frequency f,
resulting from the product of VT x f.
The ventilation pattern is defined with the ventila-
tion parameters of tidal volume VT, frequency f,
inspiration time Ti and ramp.
To prevent the mandatory ventilation stroke being
applied during spontaneous expiration, the flow
trigger of the device ensures that the mandatory
ventilation stroke is triggered within a "trigger win-
dow" with the spontaneous inspiration.
The trigger window has a maximum length of
5 seconds. At expiration times of less than
5 seconds it covers the entire expiration time,
minus a minimum expiration time of 500 ms.
Since synchronization of the mandatory ventilation
stroke reduces the effective SIMV time and thus
would undesirably increase the effective frequency,
Carina extends the following spontaneous breath-
ing time by the missing time difference
Δ
T. Exceed-
ing the SIMV frequency is thus avoided. The
factor f, responsible for minimum ventilation,
remains constant, in addition to tidal volume VT.
046
Paw
Ramp
Ramp
PEEP
Ti
t
Trigger -
window
Spontaneous
breathing time
Spontaneous
breathing time +
Δ
T
Synchronised manda-
tory ventilation stroke
Set mand.
cycle time 1
f
Set mand.
cycle time 1
f
Unsynchronised
mandatory
ventilation stroke