The First Social Network for Respiratory Care
Which mode is better, A/C or SIMV?
Which mode is better, A/C or SIMV?
Marino, Paul L. ICU Book, 3rd Edition,2007,p.478.
" In summary, IMV provides few benefits over assist-control ventilation. The principal benefit of IMV is for the patient who is breathing rapidly because volume-cycled (assist-control) ventilation for these patients creates a risk for hyperinflation, auto-PEEP, and volutrauma. The risk of ventilator-induced lung injury may be lower with IMV than assist-control because less time is devoted to volume-cycled ventilation with IMV. This, however, is unproven. Finally, IMV should be avoided in patients with respiratory muscle weakness or left-ventricular dysfunction."
JESSE B. HALL, GREGORY A. SCHMIDT, LAWRENCE D.H. WOOD,PRINCIPLES OF CRITICAL CARE, 2005. P486:
"Typically, the patient performs inspiratory work during an assist-control breath.. This may not be obvious despite careful examination of the patient unless measures of intrathoracic pressure (esophageal pressure and central venous pressure) are available, or the inspiratory pressure waveform is examined carefully (Chap 32). Effort at the end of the breath will affect the Ppk and Pplat, making determination of respiratory system mechanics unreliable. When the patient is assisting every breath, the work of breathing can be increased by increasing the magnitude of the trigger or by lowering Vt (which increases the rate of assisting; see Table 36-2). Decreasing f at the same Vt generally has no effect on the work of breathing (in contrast to SIMV, discussed below) when the patient is initiating all breaths.
The SIMV mode is often used to gradually augment the patient’s work of breathing by lowering the mandatory breath f (or Vt ), thereby driving the patient to breathe more rapidly to maintain adequate ventilation, but this approach appears to prolong “weaning’’. (seeTable 36-2). Although this mode continues to be used widely,
there is little rationale for it and SIMV is falling out of favor."
Patrick Neligan says:
"Consequently, a pressure controlled SIMV mode has been developed for partially weaned patient. Most authorities agree that SIMV volume control is a poor weaning technique, and the patient is better off fully established on pressure support or assist-control (pressure or volume) if requiring ongoing ventilation. However, for most post operative patients, heavily sedated patients and those with little lung injury, the mode used is probably irrelevant, and it is much easier to wean a patient from SIMV than from VAC.
Further, a high percentage of intensive care units worldwide use SIMV + pressure support as their prime method of ventilation, and there is little evidence that this “mixed” mode is of any harm to the patient. My recommendation is that once a patient begins to breath spontaneously, there is no indication for mandatory breaths, and the patient should be switched over to pressure support ventilation alone: gradual weaning of IMV breaths in these circumstances is unnecessary."
Link: http://www.ccmtutorials.com/rs/mv/page12.htm
In my country the general sequence of MV is to start ptn on A/C then SIMV+PS then PS alone then T piece then extubation !!!! no need for this long chin , when your ptn need MV, start him on A/C whatever the case was, if he is improving and become weanable shift him to PS ( or T piece directly in some case)…no need to go through SIMV
-------------------------------------------------------------------------
Marino, Paul L. ICU Book, 3rd Edition,2007,p.478.
" In summary, IMV provides few benefits over assist-control ventilation. The principal benefit of IMV is for the patient who is breathing rapidly because volume-cycled (assist-control) ventilation for these patients creates a risk for hyperinflation, auto-PEEP, and volutrauma. The risk of ventilator-induced lung injury may be lower with IMV than assist-control because less time is devoted to volume-cycled ventilation with IMV. This, however, is unproven. Finally, IMV should be avoided in patients with respiratory muscle weakness or left-ventricular dysfunction."
JESSE B. HALL, GREGORY A. SCHMIDT, LAWRENCE D.H. WOOD,PRINCIPLES OF CRITICAL CARE, 2005. P486:
"Typically, the patient performs inspiratory work during an assist-control breath.. This may not be obvious despite careful examination of the patient unless measures of intrathoracic pressure (esophageal pressure and central venous pressure) are available, or the inspiratory pressure waveform is examined carefully (Chap 32). Effort at the end of the breath will affect the Ppk and Pplat, making determination of respiratory system mechanics unreliable. When the patient is assisting every breath, the work of breathing can be increased by increasing the magnitude of the trigger or by lowering Vt (which increases the rate of assisting; see Table 36-2). Decreasing f at the same Vt generally has no effect on the work of breathing (in contrast to SIMV, discussed below) when the patient is initiating all breaths.
The SIMV mode is often used to gradually augment the patient’s work of breathing by lowering the mandatory breath f (or Vt ), thereby driving the patient to breathe more rapidly to maintain adequate ventilation, but this approach appears to prolong “weaning’’. (seeTable 36-2). Although this mode continues to be used widely,
there is little rationale for it and SIMV is falling out of favor."
Patrick Neligan says:
"Consequently, a pressure controlled SIMV mode has been developed for partially weaned patient. Most authorities agree that SIMV volume control is a poor weaning technique, and the patient is better off fully established on pressure support or assist-control (pressure or volume) if requiring ongoing ventilation. However, for most post operative patients, heavily sedated patients and those with little lung injury, the mode used is probably irrelevant, and it is much easier to wean a patient from SIMV than from VAC.
Further, a high percentage of intensive care units worldwide use SIMV + pressure support as their prime method of ventilation, and there is little evidence that this “mixed” mode is of any harm to the patient. My recommendation is that once a patient begins to breath spontaneously, there is no indication for mandatory breaths, and the patient should be switched over to pressure support ventilation alone: gradual weaning of IMV breaths in these circumstances is unnecessary."
Link: http://www.ccmtutorials.com/rs/mv/page12.htm
In my country the general sequence of MV is to start ptn on A/C then SIMV+PS then PS alone then T piece then extubation !!!! no need for this long chin , when your ptn need MV, start him on A/C whatever the case was, if he is improving and become weanable shift him to PS ( or T piece directly in some case)…no need to go through SIMV
-------------------------------------------------------------------------
Views: 500
Replies to This Discussion
-
Permalink Reply by Bill Garrison on -
I agree that SIMV is a useless mode. A/C is use to maintain ventilation until the lung injury or system failure is resolved. A/C conserves the body resources so the lung does less work and helps the body heal faster. When the system failure is resolved PS then T-piece then extubation is the way to go.
-
Permalink Reply by Chris on -
Simv is a mode of the past and there is little or no reason to ever use it!!
-
Permalink Reply by Prem on -
Dear Fellow RT,
Simv belongs to the Dinosaurs Era.There is enough Data to support.
Regards.
Prem.
-
Permalink Reply by marites mercado on -
what is the case of your patients? A/C and SIMV there is a different purposes or functio
-
Permalink Reply by Mark on -
I agree SIMV has virtually no application in Adult weaning. Also T-Pieces via ETT are not done at any facilities in my area. My feeling is getting to a pressure support trial without additional steps is optimal for the patient in most situations.
-
Permalink Reply by Chris on
-
I would use automatic tube compensation(ATC) instead of pressure support, if your vent offers it. ATC with appropriate PEEP is called "electronic extubation" and will more closely predict how your patient will do off the vent.
Again, There is NO indication for the use of SIMV with today's vents, I would choose MMV, we use the Drager XL.
T-piece with an ETT should be considered cruel and unusual punishment.
-
Permalink Reply by Saud AlMugaiteeb on -
A/C is the default mode for every body I guess, but I have no doubt that SIMV is a useless, confusing Mode!
the best use of SIMV is when your patient is fighting the vent and there is no ulternative, but I've never used SIMV as a weaning mode !!
once your patient's fullfill the criterias of being ready to be weand of the vent, PS is the best, harmless choise !
totally agree with you buddey !
Best Regards,
Saud
-
Permalink Reply by billy on -
yeah! i never use simv for weaning reason instead wenever pt start to breath simv can use. but weaning pt better put on TC then weaning protocol may start if passed extubate!
-
Permalink Reply by Eric Cheng on -
Guess I missed out on this discussion. But here I'm here in North America, and it seems like SIMV is not used very often. that being said, anyone have experience with (Proportional assist ventilation) PAV or (Neurally adjusted ventilatory assist) NAVA?
-
Permalink Reply by Tony on -
First let me say right up front that I think SIMV is outdated and pretty much obsolete, but as much as SIMV is outdated, so is A/C. I have a hard time with conversations like this for several reasons, first the mode is secondary to the skill of the thearpist, and aslo most of us operate under protocol devised by physicians that are not up to date on what is offered and avialable. We are also slave to the budget of the facility and the equipment that is available. Some of the best modes (although around for several years) are not used due to budget restraints, physician understanding, protocol, and even at times therapist ignorance. There is also the small facilities that do not use vents often and thus use what is easy. When speaking of lung protective ventilation A/C is not a very useful mode of ventilation compared to other modes that are available, it just happens to be a mode available on every vent on the market. When it comes to lung injury a more appropriate mode is probably APRV, or even a mode of osculating APRV available on on one ventilator that I know of the VDR. APRV is also called several other names depending on the brand of ventilator it comes on. Anyway, I guess my question is how do we drive the technology and educate the masses so that we can best care for our patients? Thanks, and sorry i'll get off my soap box now.
-
Permalink Reply by Jeff Whitnack on -
I call SIMV "Stupid Idiot Mode Ventilation". I think it initially arose as 1) early A/C was very patient unfriendly as regards spontaneous breathing---lousy trigger, lousy flow response, tethered to piston setup. Early A/C had trigger removed and IMV replaced it.....either flow by which was easier for the patient but erased volume alarms or demand valves which were sluggish and then needed PS to fix it....meanwhile the technological flaws of A/C were fixed. No need to have a "schizo" form of breathing. In early SIMV with PS I'd often see the volume "mandatory" breath have sluggish flow set which didn't unload the resistive load, then "Johnny Come Lately" the VT and elastic load unloaded. Then PS breath with good initial resistive unloading, but where's the VT beef?. or 2) SIMV was a way to charge patients for more ventilator hours when everything was fee for service and RT Dept.s were revenue centers.
SIMV has seen a bit of an "upside down" resurgance ala APRV if one views the drops as the mandatory breaths in SIMV. But this use, if one supports it, seems better for ARDS patients capable of significant amount of spontaneous breathing----say a young fireman with burn injury as opposed to the geriatric train wreck we often see with multiple medical problems. I see APRV as a valuable niche mode for certain ARDS patients.
"Hand 'em high and drop 'em quick" with Clint Eastwood spaghetti western music playing in the background.
Events
-
Sleep Asia - Introduction to Polysomnography and Sleep Disorders (3-Day)
September 13, 2012 to September 16, 2012 – Singapore
The Introductory course looks to provide a solid foundation to those just entering the Sleep Field or who have a minimal amount of experience. This course will look to solidify and consolidate basic…
Organized by Sleep Asia | Type: sleep, courses
Groups
-
PINOY RCP
52 members
-
Respiratory Therapy Stud…
56 members
-
Saudi Arabia
47 members
-
Pinoy R.T. - Dubai
11 members
-
QATAR RCP
34 members
-
king fahad hospital of t…
20 members
-
Philippine Society for t…
6 members
-
RMH
3 members
-
King Fahad Specialist Ho…
14 members
-
Filipino Respiratory The…
24 members
© 2012 Created by Mohammed A. Al Olayan.
