Synchronized Intermittent Mandatory Ventilation SIMV Objectives Understand the

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 Variable SIMV

Patient or Time Triggered

Time Cycled

Breath Sequence and Mode SIMV

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 Mandatory Pressure Or Volume Time Or Patient Spontaneous Patient Limit Cycle Time or Volume Pressure Flow

SIMV+PS (Volume Targeted Ventilation) Set PS Level Pressure (cm H 2 O) Tsynch Tsupp M Flow-cycled Flow (L/m) Volume (m. L) Time (sec)

SIMV (Volume Targeted Ventilation) Tsynch Pressure (cm H 2 O) Spontaneous Breaths Flow (L/m) Volume (m. L) Time (sec)

SIMV + PS (Pressure-Targeted Ventilation) Tsynch Pressure (cm H 2 O) Tsynch Tsupp Set PC Level Time Cycled Set PS Level Flow-cycled Flow (L/m) Volume (m. L) Time (sec)

VC-SIMV: +Efforts:

VC-SIMV/Psupp:

PC-SIMV: Spontaneous Efforts, 0 PSV

+ PC-SIMV PSupp

SIMV: No Efforts

Synchronization SIMV

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

Synchronization (SIMV+PSV) M Tsupp Tsynch Pressure (cm H 2 O) Flow (L/m) Cycles Mandatory Cycle Time Triggered window for supported breaths synchronized breaths Time (sec) M Tsynch Tsupp

Advantages and Disadvantages SIMV

Indications �Facilitate transition from full ventilatory support to partial support

SIMV ADVANTAGES DISADVANTAGES � Maintains respiratory � When used for weaning, muscle strength by avoiding muscle atrophy � Decreases mean airway pressure � Facilitates ventilator discontinuation – “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

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