PEEP in BLS?

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Our protocols actually recommend a high volume low rate (10-12ml/kg at 6-8) for hypotensive patients, most often trauma.
Wow...regional differences I guess. That's really surprising given these patients are at higher risk for ALI and 10-12 ml/kg doesn't meet any protective lung strategy at all. As long as the mean airway pressure didn't get too high, venous return would be preserved. Do your protocols recommend PEEP here as well?
 

EpiEMS

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Our protocols actually recommend a high volume low rate (10-12ml/kg at 6-8) for hypotensive patients, most often trauma.
What's the rationale behind this, if you don't mind my asking?
 

VFlutter

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Wow...regional differences I guess. That's really surprising given these patients are at higher risk for ALI and 10-12 ml/kg doesn't meet any protective lung strategy at all. As long as the mean airway pressure didn't get too high, venous return would be preserved. Do your protocols recommend PEEP here as well?
It is actually the protocol for the largest HEMS company nationwide, not regional. PEEP of 0, I time of 1.

What's the rationale behind this, if you don't mind my asking?
This podcast sums it up better than I can. The idea being that the ventilator strategy overall allows more time for venous return than conventional lung protective strategy.

http://podbay.fm/show/595147712/e/1421157181?autostart=1
 

EpiEMS

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It is actually the protocol for the largest HEMS company nationwide, not regional. PEEP of 0, I time of 1.


This podcast sums it up better than I can. The idea being that the ventilator strategy overall allows more time for venous return than conventional lung protective strategy.

http://podbay.fm/show/595147712/e/1421157181?autostart=1
Thanks for the link. Sounds like the idea is to mitigate the impediment to venous return by avoiding PEEP and allow longer periods of recovery between breaths.

He really loses me on the relationship between "dead space" and increased intrathoracic pressure though.

If I hear him correctly, he's saying that "dead space" is lost with smaller tidal volumes which somehow contributes to rising intrathoracic pressures which causes hemodynamic instability. Kind of like he's saying that dynamic hyperinflation/breath stacking is occurring, but that can't be what he's saying.

Is there a paper you could point me toward that is more clear? I must confess that I've never heard of this type of ventilation strategy and I'm interested in learning more about it.
 

VFlutter

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Thanks for the link. Sounds like the idea is to mitigate the impediment to venous return by avoiding PEEP and allow longer periods of recovery between breaths.

He really loses me on the relationship between "dead space" and increased intrathoracic pressure though.

If I hear him correctly, he's saying that "dead space" is lost with smaller tidal volumes which somehow contributes to rising intrathoracic pressures which causes hemodynamic instability. Kind of like he's saying that dynamic hyperinflation/breath stacking is occurring, but that can't be what he's saying.

Is there a paper you could point me toward that is more clear? I must confess that I've never heard of this type of ventilation strategy and I'm interested in learning more about it.
Ya I was not following that as well. He focused heavily on dead space ventilation during our ventilation modules but I am not sure I completely agree or see it in practice. Maybe he is saying since there is fixed dead space loss with each breath that what we assume are normal physiologic tidal volumes are actually much less at the alveolar level and that the compensation would be increasing respiratory rate causing more time with increased intrathroacic pressures. Assuming you have 150ml of dead space ventilation with each breath then lowering the respiratory rate would mean encountering that dead space less often? Not sure.

I will try to find the reference articles on our training modules.
 

VentMonkey

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Generally speaking, yes. But like I said before, if a low/no blood flow state were to exist, you'd leave off the PEEP and use "smaller" tidal volumes because of the potential to further decrease venous return to the heart.
Just curious, would you mind sharing your background with the group?
 

Carlos Danger

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The reasoning behind the low frequency ventilation strategy in hypotension is simple: if you minimize the amount of time that the lungs are inflated, then you minimize mean intrathoracic pressure. That's why the short i-time is important. The larger tidal volumes are simply to maintain an adequate minute volume with the lower respiratory rate. 6 breaths with an i-time of 1 and you get only 9 seconds a minute or so at the peak intrathoracic pressure. 10 breaths/min with an i-time of 1.5 and you get more than twice the amount of time at peak pressure.

I have to say though, that 10-12 ml/kg seems ridiculously high. Not only do we know that to be hard on the lungs, but you just don't need that much to maintain an adequate minute volume in a well-sedated patient. If you assume 4 l/m is an adequate minute volume in a sedated patient and you only want to ventilate 6 times a minute, then you only need 660 cc tidal volume. If you are willing to accept a little higher Pac02 then you can go even lower on your vt. I also don't see the rationale behind zero PEEP.

I don't see what anatomic dead space has to do with anything at all here. Anatomic dead space is always present and always constant, no matter what vent strategy you are using or why. The guy in the podcast honestly didn't seem to know much about what he was talking about. I've heard him say some wacky stuff in other podcasts too, including a couple things that were outright untrue.
 

VFlutter

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The guy in the podcast honestly didn't seem to know much about what he was talking about. I've heard him say some wacky stuff in other podcasts too, including a couple things that were outright untrue.
Unfortunately the majority of our training on ventilator management was written by him. Some of it was good but a lot of it was infuriating
 

E tank

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The reasoning behind the low frequency ventilation strategy in hypotension is simple: if you minimize the amount of time that the lungs are inflated, then you minimize mean intrathoracic pressure. That's why the short i-time is important. The larger tidal volumes are simply to maintain an adequate minute volume with the lower respiratory rate. 6 breaths with an i-time of 1 and you get only 9 seconds a minute or so at the peak intrathoracic pressure. 10 breaths/min with an i-time of 1.5 and you get more than twice the amount of time at peak pressure.

I have to say though, that 10-12 ml/kg seems ridiculously high.
So the goal is minimizing the intrathoracic pressure...which we do with protective lower tidal volumes.( I get that PEEP becomes more important with lower tidal volumes, but it can be added as the patient is stabilized.) I'm still lost on the point. Seems like robbing Peter to pay Paul. Additionally, won't peak pressures be higher with shorter i-times?

If an entire HEMS system is using this, my assumption is that folks smarter than me have vetted it...I'm just interested in where it comes from.
 

Carlos Danger

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If an entire HEMS system is using this, my assumption is that folks smarter than me have vetted it...I'm just interested in where it comes from.
Well, I agree.....there must be something to it. I'd like to read something on it. But there's gonna have to be some pretty overwhelming evidence to convince me that 10-12 ml/kg is a good idea.
 

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