Is SIMV an outdated setting on a ventilator? Does anyone know of any papers that would help support or argue against this? An attending asked me this and I have no idea how to answer. I'm currently in a MICU rotation and all I know is that it was used heavily in a SICU rotation I was on just 3 months ago.
SIMV Mode Outdated?
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MICU doctor? If his implication that it is outdated, then he's an idiot.
SIMV and CMV/Assist-Control can do the exact same thing, if you know how to set the ventilator. Most pulm/CC guys I know don't really think about the way they set the vent, nor do they really understand that these two settings can do the exact same thing. The difference is that in SIMV you can dial-down the mandatory breaths and let the patient's diaphragm work more with pressure support, and not get a set volume every time they trigger the vent which over-encourages muscle resting and thus atrophy.
Show him this paper:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2924757/
Your chance to teach him something.
SIMV and CMV/Assist-Control can do the exact same thing, if you know how to set the ventilator. Most pulm/CC guys I know don't really think about the way they set the vent, nor do they really understand that these two settings can do the exact same thing. The difference is that in SIMV you can dial-down the mandatory breaths and let the patient's diaphragm work more with pressure support, and not get a set volume every time they trigger the vent which over-encourages muscle resting and thus atrophy.
Show him this paper:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2924757/
Your chance to teach him something.
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I definitely wouldn't say it's outdated or that AC is an equivalent mode (or an appropriate mode for every patient).
I've had crit care docs tell me that it's very uncomfortable for patients which is why they won't use it.
I've had crit care docs tell me that it's very uncomfortable for patients which is why they won't use it.
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If you are a junior resident, most likely your attending is referring to the vent weaning paper T-piece vs PSV vs SIMV that showed shortest weaning times w/ PSV. Look it up.
To answer your first question, I'm just gonna assume that you're talking about SIMV-PSV, i.e., where additional breaths beyond the mandatory ones are pressure supported.
SIMV has a role in a modern ICU (whether MICU or SICU). In some patients. In many patients, the difference between SIMV and AC is immaterial, either because the patient is "riding" the vent or is in full PSV mode. In some, it can be huge especially those with a central hyperventilatory drive where AC can "iatrogenically" hyperventilate the patient.
Generally speaking, PSV breaths are more comfortable for the patient than mandated volume breaths. And generally speaking, having the patient do SOME amount of work of breathing is a good thing. (There are some VERY important exclusions to that statement.) So, generally speaking, I like to have patients do as much PSV as possible.
That said, for "all comers" in the ICU I don't use SIMV very much, because most go speedily from VAC to PSV to extubated. For some long-term (like many days or weeks) vent weans, SIMV can be very useful because you can really dial in how much work the patient is doing. Those are rare cases though. The problem with SIMV in the "old days" was the transition from a lot of volume controlled breaths to none took too long, and docs were inadvertently buying their patients long vent weans.
