APRV

[lymphocyte]

Are you on the APRV train? Were you always on the train? Are you skeptical?

Just published was "garbage in garbage out" meta-analysis on APRV that purports a mortality benefit in hypoxemic resp failure (NB not necessarily ARDS).

Airway Pressure Release Ventilation in Adult Patients With Acute Hypoxemic Respiratory Failure: A Systematic Review and Meta-Analysis - PubMed

In adult patients requiring mechanical ventilation for acute hypoxic respiratory failure, airway pressure release ventilation is associated with a mortality benefit and improved oxygenation when compared with conventional ventilation strategies. Given the limited number of patients enrolled in...

www.ncbi.nlm.nih.gov

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[jdh71]

Oh. Ffs. For. ****s. Sake.

It makes sense when it makes sense, *clinically*. It’s not some kind of blunt instrument we should just be going around and plugging into any and all cases.

In a case of really bad and low lung compliance ARDS tell me what the plateau pressure is in APRV and how you can determine acceptable and reasonable estimations of transpulmonary pressures especially if you are allowing the patients to spontaneously breathe above your bilevel settings! And if you aren’t letting them spontaneously breathe then you aren’t really even using APRV.

It *is* a fantastic way to improve mean airway pressures. There are times for reasons that I have yet to been able to predict in my patients when it is the mode of ventilation that will give me the highest SpO2 (though this isn’t a marker for survival now is it?). I do like it’s use on my ECMO patients - keeping lungs open with very low (assumed) driving pressures the way I set it up and very low lung volumes on “release”. You can do basically the exact same thing in other modes but this seems really easy for my brain to wrap itself around in this situation.

 

[lymphocyte]

It makes sense when it makes sense, *clinically*. It’s not some kind of blunt instrument we should just be going around and plugging into any and all cases.

And when did low tidal volume make sense *clinically*? The point is that it didn't, until ARDSNet was published. After that, low tidal volume started making a lot of sense.

Now, many intensivists seem to plug it into any and all cases cases, like a blunt instrument, when really it's just for that unpredictable subset of patients who truly have ARDS. And yet, overall, despite being treated like a blunt instrument, it's saved a lot of lives.

If you're ONLY using APRV in niche situations like hypoxemic rescue, then maybe (MAYBE) you might be causing harm -- the overall signal in the literature seems to be that it should be used much more permissively as opposed to something else.

 

[jdh71]

And when did low tidal volume make sense *clinically*? The point is that it didn't, until ARDSNet was published. After that, low tidal volume started making a lot of sense.

Now, many intensivists seem to plug it into any and all cases cases, like a blunt instrument, when really it's just for that unpredictable subset of patients who truly have ARDS. And yet, overall, despite being treated like a blunt instrument, it's saved a lot of lives.

If you're ONLY using APRV in niche situations like hypoxemic rescue, then maybe (MAYBE) you might be causing harm -- the overall signal in the literature seems to be that it should be used much more permissively as opposed to something else.

I don’t think I’ve seen any data supporting WHEN you should use APRV and as such the only thing that makes sense to me IS niche use when you have a specific clinical end point in mind and APRV best gets you there.

 

[Hamhock]

I use it when the doc before me has started it (as a rescue therapy, usually).

However, as @jdh71 said, basically the same thing can be done with other modes of ventilation.

That said, I basically see no reason why it would ever need to be used. Appropriate use of early PEEP (ideally based on something like esophageal pressures, if available) and appropriate "extra-pulmonary" therapies (eg minimizing cyrstalloid, blood transfusion, NMB, etc) will basically eliminate the need for APRV.

Any benefit for APRV in all comers (eye roll) is, I would bet, due to the use of "early PEEP" the Phigh provides. For some reason people are cool with APRV Phigh 30 but freak the hell out when the PEEP is set at 20. I just don't get it.

HH

 

[lymphocyte]

I don’t think I’ve seen any data supporting WHEN you should use APRV and as such the only thing that makes sense to me IS niche use when you have a specific clinical end point in mind and APRV best gets you there.

Most of the trials have looked at pAFi < 300. Very broad indication.

 

[lymphocyte]

I use it when the doc before me has started it (as a rescue therapy, usually).

However, as @jdh71 said, basically the same thing can be done with other modes of ventilation.

That said, I basically see no reason why it would ever need to be used. Appropriate use of early PEEP (ideally based on something like esophageal pressures, if available) and appropriate "extra-pulmonary" therapies (eg minimizing cyrstalloid, blood transfusion, NMB, etc) will basically eliminate the need for APRV.

Any benefit for APRV in all comers (eye roll) is, I would bet, due to the use of "early PEEP" the Phigh provides. For some reason people are cool with APRV Phigh 30 but freak the hell out when the PEEP is set at 20. I just don't get it.

HH

Maybe. But APRV also provides greater duration at high PEEP as it's time triggered and time cycled. The conceptual point is to keep alveoli open, and maybe that's where the merit lies.

Also, the largest trial using oesophageal monitoring published just this year in JAMA was a negative trial.

Beitler H, et al. Effect of Titrating Positive End-Expiratory Pressure (PEEP) With an Esophageal Pressure-Guided Strategy vs an Empirical High PEEP-Fio2 Strategy on Death and Days Free From Mechanical Ventilation Among Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial. JAMA. 2019;321(9):846-857.

PubMed

PubMed® comprises more than 38 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full text content from PubMed Central and publisher web sites.

www.ncbi.nlm.nih.gov

 

[jdh71]

Most of the trials have looked at pAFi < 300. Very broad indication.

So? You think it's some kind of magic? It's not. I think perhaps everyone goes through an "APRV is the magic bullet everyone is missing" phase. It's like the terrible twos.

 

[lymphocyte]

So? You think it's some kind of magic? It's not. I think perhaps everyone goes through an "APRV is the magic bullet everyone is missing" phase. It's like the terrible twos.

I don't think it's magic at all. My experience is limited. I'm just curious about it.

How to safely ventilate a spontaneously breathing hypoxemic patient seems like such a basic question, and yet the practice pattern is so bizarrely varied. For example, there's a massive geographical divide in Australia, East vs West regarding APRV. Why? I don't know. I also don't understand why it dominates in the SICU literature. The heterogeneity seems to suggest we actually don't know what we're doing.

The response might be, it all depends on the patient in front of you. But you often can't detect harm or benefit for the patient in front of you, except in the extreme -- even ARDSNet has NNT greater than 1. Yes, you can do magical things with PEEP or APRV in rescue situations, but my question is much more mundane -- what should we be doing most of the time?

 

[lymphocyte]

So? You think it's some kind of magic? It's not. I think perhaps everyone goes through an "APRV is the magic bullet everyone is missing" phase. It's like the terrible twos.

Also, on the very question of "magic" -- there's mechanistic data to support APRV as a preventative strategy for ARDS.

Nader Habashi: Airway Pressure Release Ventilation (APRV) – A mechanistic and physiologic view | University of Maryland

maryland.ccproject.com

 

[Hamhock]

but my question is much more mundane -- what should we be doing most of the time?

Most of the time? Meaning true ARDS (rarer than most think) and other hypoxemic conditions?

If you mean all hypoxemic folks, then I say using a PEEP-appropriate strategy ("high" PEEP in the mind of most) is best. The appropriate PEEP is best determined -- in my experience and by the literature, to some extent -- is measured by esophageal pressure monitoring. That PEEP may be just a bit below Phigh. A low-tidal volume will then give a low driving pressure and a high mean airway pressure; very similar to APRV.

I always want to ask the APRV folks, what are you using for the Phigh determination? Esophageal pressure monitoring? PV curves?

Are the APRV folks just estimating the mean airway pressure on top of optimized PEEP (based on esophageal pressure monitoring) for their Phigh?

When these questions are asked of APRV folks, I suspect their 'magic' will be shown to be just confusion.

HH

 

[jdh71]

I don't think it's magic at all. My experience is limited. I'm just curious about it.

How to safely ventilate a spontaneously breathing hypoxemic patient seems like such a basic question, and yet the practice pattern is so bizarrely varied. For example, there's a massive geographical divide in Australia, East vs West regarding APRV. Why? I don't know. I also don't understand why it dominates in the SICU literature. The heterogeneity seems to suggest we actually don't know what we're doing.

The response might be, it all depends on the patient in front of you. But you often can't detect harm or benefit for the patient in front of you, except in the extreme -- even ARDSNet has NNT greater than 1. Yes, you can do magical things with PEEP or APRV in rescue situations, but my question is much more mundane -- what should we be doing most of the time?

Most of the time? The answer is: whatever. You treat your patient. Many awake and spontaneously breathing patients HATE HATE HATE APRV so you have to sedate them more. Is it good to sedate patients higher so your pet mode of ventilation can get applied every time? No. That would be stupid. You apply the very minimum amount of necessary support to augment the struggling physiology. Most of the time you will want a mode of ventilation that keeps the lung open and can tell you and allow you to control volume and know plateau and driving pressure even if you aren’t already dealing with a syndrome you are calling “ARDS”. APRV then fails in a mode by my definition that you will want to use most of the time.

 

[SurfingDoctor]

My experience. All it does it make us put patients on the oscillator when it’s too late.

 

[lymphocyte]

Most of the time? The answer is: whatever. You treat your patient. Many awake and spontaneously breathing patients HATE HATE HATE APRV so you have to sedate them more. Is it good to sedate patients higher so your pet mode of ventilation can get applied every time? No. That would be stupid. You apply the very minimum amount of necessary support to augment the struggling physiology. Most of the time you will want a mode of ventilation that keeps the lung open and can tell you and allow you to control volume and know plateau and driving pressure even if you aren’t already dealing with a syndrome you are calling “ARDS”. APRV then fails in a mode by my definition that you will want to use most of the time.

There's generally higher sedation requirements for low tidal volume strategies, which is borne out in the literature.

I have NO pet mode of ventilation. I'm just looking for cogent arguments for or against.

 

[jdh71]

There's generally higher sedation requirements for low tidal volume strategies, which is borne out in the literature.

I have NO pet mode of ventilation. I'm just looking for cogent arguments for or against.

I gave you few for it not being the go to mode. I also gave you a few good reasons when to use it.