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Respkid
Is your real name Mark by chance?

As far as your post, is ATC better than PS yes. But lets not put it all on what the vent shows on its screen. Does the Vent show decelerating flows in PS and sinusidal with ATC, Yes that is not in question. What I am saying is lets look at what the patient actually sees. Remember what the vent shows is being done at the patient wye, not the bottom of the ETT. In PS the flow is delivered to the top of the ETT with a decelerating waveform, however the bottom of the ETT is seeing something completely different. With a decelerating flow waveform the first part of the breath has the fastest flow and hince the highest Raw so the ETT will absorb the highest amount of pressure and slow the flow down the most. As the breath continues the breath slows down and the Raw decreases becasue of this, as this happens the flow does not slow down as much as it did at the beggining of the breath. And so forth and so forth through the entire breath. So is the patient (bottom of the ETT) seeing a decelerating flow waveform or a sinusidal? I believe they are seing more of a sinusidal than a decelerating breath. Now the push vs a pull mechansim (Dr. Habashi's favorite) does this hold tru Yes if the Ps is too high. However if the bottom of the ETT is seing no pressure change on one breath (we some how set the PS perfect) then the patient is pulling the breath in not having it pushed. If we have the PS set to high and the patient is seeing, lets say 2cmH2O (at the bottom of the ETT) and their Cs is 30ml/cmH20, then yes 60 ml is being delivered to their lungs with the given PS. If the PS is set too low then then not all of the Raw of the ETT is taken care of and the patients WOB is higher than need be.

I agree with all of this, but what is a Therapist going to do if they have a Servoi, or 840 (that can not add Tc to APRV)? Are they supposed to not add PS and help the patient with Raw associated with the ETT, and in return greatly increase their WOB? or Add LOW levels of PS knowing that on any given breath they may being giving to much and pushing small amounts of volume, or not giving enough support, or being just right?

That last sentence sounds alot like the three bears. This pressure support is toooo much, this one is not enough, but this one is Just right


Light
 
Posts: 104 | Location: Springfield, MO | Registered: March 08, 2004Reply With QuoteReport This Post
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respkid,
Are you using the computer software with the michigan so you can see the graphs with it as well? I do not want to give away all of our study, but if you look at the graphs instead of just the pressure manometer, you will see what I am seeing. The pressure manaometer shows raises in pressure with NO PS, ATC, PS 2, 4, 6, 8, 10............. this raise in pressure is when the coil of the michigan pulls back down on the test lung right at the end on the breath going in, NOT during flow going into the lung. More to come as soon as they allow my last two posts to go through, mine always seem to get censored.


Light
 
Posts: 104 | Location: Springfield, MO | Registered: March 08, 2004Reply With QuoteReport This Post
<respkid>
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I have not read your previous post since they have not been posted yet, but I will continue with what we have found. We actually have the michigan test lung that measures actual volume, pressure and flow seen by the lung and at the proximal airway as well as the proximal pressure manometer and graphics package. With bilevel set at PEEPH 20 PEEPL 0 THIGH 6 Tlow 0.7 with a pressure support of 30 and an 6.0 ETT. We are seeing intrapulmonary pressures 10 above the PEEPH or 30 cmH20 with spontaneous effort during THIGH. This corresponds with flow going into the lung and not the recoil of our test lung. In fact our PB Rep has told us that if we use Bilevel with PS to lower the PEEPH by the amount of pressure support set above the PEEPH. In other words in the test described above we should set the PEEPH at 10cmH20 with a PS of 20cmH20. Obviously this makes no sense to the clinician but perfect sense to a sale rep Smile
 
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<rtnovice>
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Wow, this discussion has taken on a life of its own. Is there a PB Rep or other clinician on the board that can confirm the findings of either Light or respkid?
 
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I am still waiting for some of my previous post, but here goes anyways. Respkid, using you michigan place the patient on Bilevel with tube comp on and then have the Michigan trigger breaths at volumes of 250-300ml. You will see raises in the intrapulmonary pressures, are you then going to tell me not to use tube comp? This raise in intrapulmonary pressure with raises in volume make sense. if you add volume to the lung it must make a pressure, right. What I am looking at is the pressure at the bottom of the ETT, when michigan is intubated with a ETT. We are not seeing rasies in pressure at spontaneous breaths of 250-300ml when compared to no PS at all, untill we reach PS of >10 (depending on the size of the ETT)

I will state it another way. Before tube comp, at what PS would you be willing to extubate someone? Why is this so? Is it because you knew that pressure on average was only overcoming the Raw of the ETT?

How does ATC overcome the Raw of a ETT? By adding pressure and flow at a rate that only overcomes the Raw. If you do not have tube comp why can you not add Low levels of support to do the samething?

As far as the Rep saying the drop the Phigh, that is plain stupid!

What I ask again, is what are Servoi users supposed to use to overcome the Raw of the ETT and decrease the WOB of their patients that are in BIvent?


Light
 
Posts: 104 | Location: Springfield, MO | Registered: March 08, 2004Reply With QuoteReport This Post
<brandx>
posted
I think one of the biggest differences between PS above PEEPH and TC above PEEPH is pressure support provides a fix pressure/flow whereas TC provides a dynamic pressure and flow based on the patients demands.

There are countless articles out there discussing the advantages of spontaneous breathing over pressure support as it relates to cardiac output and recruitment. I guess if you don't have the ability to use TC at PEEPH you purchased the wrong vent..ha ha
 
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<respkid>
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Light,

Excellent points my friend. However we are forgetting to mention intrapleural pressure which depends on a variety of factors; body position, the heart, chest wall and most importantly with our discussion the position of the diaphragm. Unfortunately our test lung can not simulate the movement of the diaphragm; a crucial component when discussing PS and ATC on top of PEEPH. Also PS supplies a fixed pressure/flow; ATC applies a pressure/flow based on patient effort and that flow is distributed to the dependent, posterior lung segments while the pressure supported flow will be delivered to the anterior less dependent areas of the lung leading to overdistension.

I'll you this question; what did you do to overcome RAW with Bilevel/APRV for ATC?
 
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What do you mean "What did you do to overcome Raw with Bilevel/APRV for ATC"? ATC's Job is to overcome Raw associated with the ETT.

I am not wanting to look at intrapleural pressures becasue it depends on some many different factors, but here goes. If we are only delivering enough flow to overcome the Raw associated with the ETT then the diaphram is still going to have to move to pull in the vollume of gas that the patient needs. However I still am NOT saying in anyway that PS is better than ATC. If you have ATC or AAC use them and not PS, they are better solutions to the problem of Raw (for the reasons that were mentioned by Respkid). But I ask again what is a therapist using the Servoi supposed to do to overcome the WOB caused by the RAW of the ETT in Bivent?

Believe it or not I am actually a Drager user and a gun put to my head I would rather use a Drager than the Servoi, but my hospital has both and when article came out and said not to PS because of the "possibility" of alveolar overdistenstion it made me think.

This message has been edited. Last edited by: light,


Light
 
Posts: 104 | Location: Springfield, MO | Registered: March 08, 2004Reply With QuoteReport This Post
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Respkid
and whoever else. My posts that had posted are now posted, but they are further up in the postings. They are from October 9th


Light
 
Posts: 104 | Location: Springfield, MO | Registered: March 08, 2004Reply With QuoteReport This Post
<respkid>
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Light,

I apologize, my thumbs got in the way on an earlier post. My question to you is this; what did you do to overcome the resistance of the artificial airway duirng APRV before ATC?
 
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