Table of Contents - Covidien

D.3 SIMV mode
Breath delivery
During SIMV, the ventilator can deliver a combination of mandatory
and spontaneous breaths. The ventilator, operator, or patient can
trigger mandatory breaths. The patient can also trigger spontaneous
breaths. Spontaneous breaths can be augmented by PSV.
D.3.1 Breath timing
In SIMV, a breath period (T b ) is divided into two intervals: a mandatory
interval (T m ) and a spontaneous interval (T s ) (Figure D-2).
T m
T b
Figure D-2. SIMV breath period intervals
During T b , the ventilator typically delivers one mandatory breath,
and the patient may trigger a number of spontaneous breaths.
When T b begins, the ventilator enters T m . If the patient triggers a
breath during T m , a PIM breath is delivered, the T m terminates
(regardless of whether the full T m has elapsed), and the ventilator
enters and remains in T s until T b has elapsed (Figure D-3).
Tm
T s
PIM
T m T s T m T s
T m = up to 60% of T b
T s extension
Figure D-3. Synchronizing breath intervals with patient effort
If the patient triggers a breath during T s , the ventilator delivers a
spontaneous breath based on the SUPPORT PRESSURE setting
(Figure D-4). On the 760 Ventilator, a spontaneous breath is also
based on the RISE TIME FACTOR and EXH SENSITIVITY settings.
700 Series Ventilator Operator’s Manual 10066984 Rev. D D-5
T s
7-00136
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