Question about flow, PEEP

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What is the difference between flow on a HFNC device vs PEEP on a CPAP machine? Also, when weaning from a CPAP to HF, how do you best adjust the flow to account for the previous PEEP?

 

[Hernandez]

Short answer is you don't.

Long answer is a high flow will have some peep but it's trying to oxygenate by providing enough flow that you're providing a precise fio2 by not over breathing flow and mixing ambient air, so don't worry about the peep

 

[jdh71]

What is the difference between flow on a HFNC device vs PEEP on a CPAP machine? Also, when weaning from a CPAP to HF, how do you best adjust the flow to account for the previous PEEP?

Well. HF improves oxygenation largely through and increased fraction of oxygen inhaled and the CPAP largely improves oxygenation by increasing mean airway pressure which improves alveolar ventilation. Making it s bit more confusing is that enough HF can give you some "peep" and you can run an increased FiO2 through the CPAP.

How to best adjust? Do you believe your SpO2? And there is almost never a good reason not to. Just adjust to the sat.

 

[Random Anesthesiologist]

Do you need to improve ventilation or oxygenation? If you are ventilating appropriately, switch to HFNC.

 

[jdh71]

Do you need to improve ventilation or oxygenation? If you are ventilating appropriately, switch to HFNC.

CPAP isn't going to improve ventilation either.

 

[Random Anesthesiologist]

CPAP isn't going to improve ventilation either.

That's not what I implied.

 

[jdh71]

That's not what I implied.

Of course that is what you implied, but not saying use HFNC or CPAP.

 

[Random Anesthesiologist]

Of course that is what you implied, but not saying use HFNC or CPAP.

No, the next logical sequence if cpap with peep doesn't cut it to go to HFNC, go to bipap. HFNC can generate a decent peep of its own, peep will assist with alveolar ventilation.

You don't have to argue just to argue.

 

[jdh71]

No, the next logical sequence if cpap with peep doesn't cut it to go to HFNC, go to bipap.

You don't have to argue just to argue.

I'm not arguing to argue but that is just plain wrong and stupid. You start with HFNC and then move to noninvasive CPAP/BiPAP if that isn't working. It's becoming very hard to take anything you are saying seriously now. And because of that I finding it extra precious that you are accusing me of arguing just to argue when you are so wrong. It's not some kind of nuanced point. I'm not going to let what you say stand when it's incorrect.

 

[Random Anesthesiologist]

I'm not arguing to argue but that is just plain wrong and stupid. You start with HFNC and then move to noninvasive CPAP/BiPAP if that isn't working. It's becoming very hard to take anything you are saying seriously now. And because of that I finding it extra precious that you are accusing me of arguing just to argue when you are so wrong. It's not some kind of nuanced point. I'm not going to let what you say stand when it's incorrect.

Stop being so mad and throwing hyperbole. You are saying the same thing I just said. You do this crap in off topic all the time. Stop.

 

[jdh71]

Stop being so mad and throwing hyperbole. You are saying the same thing I just said. You do this crap in off topic all the time. Stop.

I'm not mad. There was no hyperbole.

Make me.

 

[Random Anesthesiologist]

I'm not mad. There was no hyperbole.

Make me.

Make you? Is this junior high?

 

[jdh71]

Make you? Is this junior high?

I don't know. You keep crying about it? Is it?

 

[Hernandez]

No, the next logical sequence if cpap with peep doesn't cut it to go to HFNC, go to bipap. HFNC can generate a decent peep of its own, peep will assist with alveolar ventilation.

You don't have to argue just to argue.

Well you are being a bit smushy with terminology. For instance What's "cpap with peep"?

 

[Random Anesthesiologist]

Well you are being a bit smushy with terminology. For instance What's "cpap with peep"?

Sorry, I was just using what I thought the OP was saying. I'm kind of confused at to what they meant by "peep on a cpap machine" since cpap is peep.

But when I say oxygenation vs ventilation, I mean if the issue is just oxygenation and cpap is overkill, then HFNC might be a good next step. I kind of thought it was understood that if ventilation was more the issue then you would reevaluate your cpap appropriateness.

 

[Mad Jack]

Sorry, I was just using what I thought the OP was saying. I'm kind of confused at to what they meant by "peep on a cpap machine" since cpap is peep.

But when I say oxygenation vs ventilation, I mean if the issue is just oxygenation and cpap is overkill, then HFNC might be a good next step. I kind of thought it was understood that if ventilation was more the issue then you would reevaluate your cpap appropriateness.

I get what you're saying. We used to use HFNC in our hard to wean MICU patients that were ventilating properly but had high oxygen requirements. There's a select area between CPAP and high flow mask oxygen devices that HFNC fits really well within.

What is the difference between flow on a HFNC device vs PEEP on a CPAP machine? Also, when weaning from a CPAP to HF, how do you best adjust the flow to account for the previous PEEP?

HFNC generates some degree of PEEP from flow, but it is highly variable and not really comparable to what you get out of a CPAP machine. Patient sleeping with their mouth open? Kiss that PEEP effect mostly goodbye. If their respiratory rate goes up, your PEEP effect is going to decline. More flow nets you more PEEP, but it really isn't as direct an effect as with CPAP due to circuit back pressure caused by turbulent flow screwing things up at higher flow rates.

The bottom line- if they are unstable, CPAP is the appropriate choice between the two for them if they either require PEEP or a high flow oxygen mask can't keep up with their O2 demand. If they're stable and you want to step down from CPAP, or give them a temporary setup to eat with, HFNC is on the menu as an option. Certain types of patients can really benefit from HFNC, such as end-stage COPDers that can compensate on the ventilation front but have reached the point that a pendant cannula just can't cut it anymore, or patients with pulmonary fibrosis that just need a little extra something to help fight that increased elastic pressure and prevent airway collapse. Just don't overestimate its utility, as it is no replacement for some honest-to-God pulmonary edema-fighting PEEP.

That's just like, my opinion though. Everybody has their own way of handling HFNC.

 

[Random Anesthesiologist]

Great way to look at it. Another example I think of is the esophagectomy who can't have cpap, and HFNC can serve them well.

 

[Instatewaiter]

Well you are being a bit smushy with terminology. For instance What's "cpap with peep"?

I tried CPAP without peep on someone the other day. Apparently suffocation is frowned upon by our city's police department.

 

[G-Man82]

You guys are talking about the real HFNC that can deliver 60+ L/min oxygen, correct? As in trade name OptiFlow? Those devices are great. I use them more and more in some of the medical overflow patients I get in my SICU. Some of my Cardiothoracic patients benefit from them it as well, including my current preop heart failure patient still being optimized for the OR.


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[Hernandez]

I tried CPAP without peep on someone the other day. Apparently suffocation is frowned upon by our city's police department.

So you used bilevel [emoji23]

 

[Laryngophed]

Well. HF improves oxygenation largely through and increased fraction of oxygen inhaled and the CPAP largely improves oxygenation by increasing mean airway pressure which improves alveolar ventilation. Making it s bit more confusing is that enough HF can give you some "peep" and you can run an increased FiO2 through the CPAP.

How to best adjust? Do you believe your SpO2? And there is almost never a good reason not to. Just adjust to the sat.

Even if you don't believe it, an ABG is easy to get most of the time. And when it correlates to your SpO2, just start believing it. Unless there is a methylene blue fairy at your hospital.

 

[Laryngophed]

I tried CPAP without peep on someone the other day. Apparently suffocation is frowned upon by our city's police department.

The really sad thing is I saw this happen once. RT connected the circuit to the mask, mask to the patient, and didn't have a power cord for the machine. Just left it on while they went to find a cord. We (the team) were sitting in the swamp having a lecture when the alarms started going off and the nurses came to get us. I'm at the same place for residency that I was as a student, and I double check that RT after every single encounter now because of this.