Synchronized Intermittent Mandatory Ventilation: SIMV
Objectives Understand the different breath types with
SIMV Know the Phase variables of the different
breath types: trigger/limit/cycle Know the breath sequence with SIMV Controlled variables: PC-CMV vs VC-CMV Understand the synchronization mechanism Initial settings of SIMV Adjustment of SIMV Indications, advantages and disadvantages
Phase VariableSIMV
Patient or Time Triggered
Time Cycled
Breath Sequence and ModeSIMV
IMV and SIMV Periodic volume or pressure targeted breaths
occur at set interval (time triggering) Between mandatory breaths, the patient
breathes spontaneously at any desired baseline pressure without receiving a mandatory breath Patient can breathe either from a continuous flow or
gas or from a demand valve
SIMV/PS: Phase and Control Variables
Breath Type
Control Trigger Limit Cycle
Mandatory PressureOr
Volume
Time Or
Patient
Time or
VolumeSpontaneou
sPatient Pressure Flow
Flow(L/m)
Pressure(cm H2O)
Volume(mL)
MTsuppTsynch
Set PS Level
Flow-cycled
Time (sec)
SIMV+PS(Volume Targeted Ventilation)
Flow(L/m)
Pressure(cm H2O)
Volume(mL)
Spontaneous Breaths
Time (sec)
SIMV(Volume Targeted Ventilation)
Tsynch Tsynch Tsynch
Flow(L/m)
Pressure(cm H2O)
Volume(mL)
Tsupp
Tsynch
Time Cycled Flow-cycled
Tsynch
Set PC Level Set PS
Level
Time (sec)
SIMV + PS (Pressure-Targeted Ventilation)
VC-SIMV: +Efforts:
VC-SIMV/Psupp:
PC-SIMV: Spontaneous Efforts, 0 PSV
PC-SIMV+ PSupp
SIMV: No Efforts
SynchronizationSIMV
Synchronized IMV
Operates in the same way as IMV except that mandatory breaths are normally patient triggered rather than time triggered (operator set the volume or pressure target)
As in IMV, the patient can breathe spontaneously through the ventilator circuit between mandatory breaths
Synchronized IMV
At a predetermined interval (respiratory rate), which is set by the operator, the ventilator waits for the patient’s next inspiratory effort
When the ventilator senses the effort, the ventilator assists the patient by synchronously delivering a mandatory breath
Synchronized IMV
If the patient fails to initiate ventilation within a predetermined interval, the ventilator provides a mandatory breath at the end of the time period
Time (sec)
Flow(L/m)
Pressure(cm H2O)
Cycles
Triggered window for supported breaths
Triggered window for synchronized breaths
Mandatory Cycle Time
M Tsupp Tsynch M Tsynch Tsupp
Synchronization (SIMV+PSV)
Advantages and DisadvantagesSIMV
Indications
Facilitate transition from full ventilatory support to partial support
SIMV
ADVANTAGES
Maintains respiratory muscle strength by avoiding muscle atrophy
Decreases mean airway pressure
Facilitates ventilator discontinuation – “weaning”!
DISADVANTAGES
When used for weaning, may be done too quickly and cause muscle fatigue
Mechanical rate and spontaneous rate may asynchronous causing “stacking” May cause barotrauma
or volutrauma
IMV: Stacking When used for weaning, may be
done too quickly and cause muscle fatigue
Mechanical rate and spontaneous rate may asynchronous causing “stacking” May cause barotrauma or volutrauma
Thank You