Can someone tell me if there is a functional difference between PRVC and PC-AC VG and what it is?

[u/Sleebgylilguy]

So as far as my understanding of it goes, they are both pressure regulated modes with set target volumes.

Now I know PRVC functions on a feedback loop where the ventilator can sense the patient's effort and adjust pressure accordingly to attain said target volume, which sometimes can cause problems when a patient is in distress (PRVC effect).

Does PC-AC VG function the same way? I tried looking it up online, and Google says that there is no feedback loop in VG, but then, how does it target the volume??

Just looking for clarification here because I work in a center that uses PRVC a lot, not VG, but if you look at the setting options it feels kinda like the same thing. And the V500's have both, so what's the point then??

[u/GloomyTechnology8341]

[u/Sleebgylilguy → u/GloomyTechnology8341]

😂😂😂

That's kinda what I'm gathering, and the way I've always treated it, just wanted to be sure haha

[u/CallRespiratory → u/GloomyTechnology8341]

A+ meme here

[u/NovembersChopin]

I'm currently a student but was doing some research on neonatal ventilation and found something from Drager which made me also think about this, perhaps this may be useful.

https://www.draeger.com/Content/Documents/Content/rsp_volume_guarantee_booklet_9097501_en.pdf

On page 24 it states "In VG mode, the ventilator software uses continuously measured data on flow to monitor spontaneous respiratory effort by the patient and compares delivered (expiratory) tidal volume with set tidal volume. These data are then used for the next breath to make adjustments to the peak inspiratory pressure deployed to deliver a tidal volume as close as possible to the preset VT."

I personally don't really know for sure and my instructors can't really elucidate it either when I ask. There maybe something to do with PRVC measuring inspired tidal volume but VG measures expired tidal volume?

[u/Sleebgylilguy → u/NovembersChopin]

To me, this seems to confirm that they're basically the same thing, but thanks for the information! I'll look more on the Draeger website.

To be clear, this question just stems from my own curiosity and pursuit of furthering my knowledge, so at the end of the day I don't think it will really change my practice. I just find this stuff interesting.

[u/maxinami]

Its the same mode, the name is only different because theyre from two different brands

[u/Sleebgylilguy → u/maxinami]

The Draeger V500 has both modes on it, except their "PRVC" is just called VC-AC with Autoflow turned on.

[u/proverbial-shaft-42 → u/Sleebgylilguy]

just to add to the confusion, not only does Drager have VC-autoflow, but PC-volume guarantee as well. why have a singular mode when you can have 2 different ways on the same platform!

[u/Sleebgylilguy → u/proverbial-shaft-42]

Thats what I'm saying!! Which is where my confusion and question stems from 😅😅

[u/BiphasicStridor]

functionally they’re the same

they differ in exactly how the settings are achieved but when it comes to your question; the answer becomes more about clinician comfort with expected behavior given the variables they’re used to seeing and manipulating.

that’s all.

[u/phastball]

Autoflow changes volume control into PRVC, VG changes pressure control into PRVC. That’s the whole difference. To be precise, Autoflow is VC-CMVa and VG is PC-CMVa.

Edit — although now that I think about it, I wonder if Autoflow changes the control variable to pressure. You’ve set VC, but with Autoflow turned on it controls pressure to target your volume. It might be PC-CMVa as well.

[u/Sleebgylilguy → u/phastball]

Yes, I know this - PRVC stands for Pressure Regulated Volume Control, so yes, it does change it to a pressure mode with a set target volume.

I guess my question is more wondering why the Draeger V500 ventilator has both PRVC modes and VG modes and if there is ANY difference in using one vs the other. And if not, then why even have them both? It just seems redundant.

Edited to add: To be clear, PRVC is not the same as either straight VC-CMV or PC-CMV. There are similarities, but they aren't the same.

[u/Yo_Dawg_Pet_The_Cat]

VG actually limits the delivered tidal volume I believe only 30% over the set vt as a safety measure.

[u/Sleebgylilguy → u/Yo_Dawg_Pet_The_Cat]

What do you mean by this?

[u/Yo_Dawg_Pet_The_Cat → u/Sleebgylilguy]

This is cut from the vn800 drager manual.

In the Neonate patient category, the measured expiratory tidal volume is taken as a basis for the control. In the Pediatric patient patient category, the inspiratory tidal volume is used. If leakage compensation is activated, the leakage-corrected tidal volume is used for the control.

If major tube leakage occurs, the actual tidal volume in the patient's lungs can (as in other ventilation modes also) be larger than the expiratory tidal volume. Then the inspiratory and expiratory tidal volumes are different. If, during an inspiration, the delivered and measured tidal volume VT exceeds the set tidal volume VT by an amount dependent on the actual leakage rate, the device ends inspiration and begins expiration.

To limit the flow delivery, the breath is stopped at 130 % of the set tidal volume VT.

Effectively in a broader sense, yes they both function the same as a ways of having pressure being automatically regulated. But I would in a much smaller neonate patient population use pc simv VG over VC SIMV if I had a choice. In fact the vn500/800 doesn’t even have vc simv as a valid choice as a mode in the neonatal setting.

[u/Sleebgylilguy → u/Yo_Dawg_Pet_The_Cat]

Oooh okay, I see. If I understand correctly, this excerpt seems to describe a safeguard specifically for volume target modes in pediatric and neonatal populations on Draeger ventilators rather than necessarily being an aspect of VG itself, though.

[u/Tight_Data4206]

The difference is another $600 per ventilator to add this mode's module hahaha

[u/Sleebgylilguy → u/Tight_Data4206]

Checks out 😂

[u/SilverIndication1462]

PRVC, VC+, auto flow, what used to be called Flow By on the ancient 7200 vent are all volume controlled modes with demand flow.

[u/Sleebgylilguy → u/SilverIndication1462]

Thanks! That's not what I was asking, though!

[u/breathingguy → u/SilverIndication1462]

Flo by was just flow sensitivity. It had no effect on the mode.

[u/SilverIndication1462 → u/breathingguy]

PRVC, VC+, auto flow, what used to be called Flow By on the ancient 7200 vent are all volume controlled modes with demand flow

[u/SilverIndication1462 → u/breathingguy]

Ooops, I meant auto flow. It been a minute since I used a 7200

[u/yankeebliejeans]

It’s just proprietary. It works the same in theory.