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Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
#71
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
(11-24-2017, 09:46 PM)Sleepster Wrote:
(11-19-2017, 07:54 PM)Sleeprider Wrote: What all this means is you need to be aware of the impacts of using EPR or Flex.  Expect that with auto pressure, the pressure will be higher than your titrated CPAP pressure without pressure relief.

In my case and I suspect a lot of, if not most, others the pressure doesn't go up. I rarely if ever go above my titrated pressure of 13 cm regardless of how large I set my pressure support. Expect something to happen if you know for sure it doesn't happen?!

You're not using a Resmed AirSense 10 machine.  You're using a VPAP machine.  It correctly discloses the EPAP pressure, unlike the AirSense 10 which only displays the IPAP pressure.  I would not expect you to see any difference in the auto-titrated EPAP as you adjust pressure support on the VAUTO.
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#72
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
Reznik,
Let me try one more time. It doesn't take as much pressure to hold your airway open when your breathing out because the air your breathing out helps keep your airway open. The amount of pressure needed on exhale may vary but the fact is the air you breath out does assist in keeping the airway open. If you don't agree with that than I just have to say we disagree and I'll move on.
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#73
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
(11-24-2017, 11:22 PM)Walla Walla Wrote: Reznik,
             Let me try one more time.  It doesn't take as much pressure to hold your airway open when your breathing out because the air your breathing out helps keep your airway open. The amount of pressure needed on exhale may vary but the fact is the air you breath out does assist in keeping the airway open. If you don't agree with that than I just have to say we disagree and I'll move on.

No, that's not correct.  It takes the same amount of pressure to hold your airway open at all times.  Your effort in breathing out (and in breathing in) may provide some of the force that is necessary to maintain that pressure, but the amount of pressure required to hold your airway open is the same.

Let's try to understand this using an analogy.  Suppose you have in inner tube, with three holes in it.  At atmospheric pressure, the innertube is flat.  No air passes through it.  Suppose that you need 15 units of pressure to open it up so that air can pass through it.  Less than 15 and it collapses, more than 15.5 and it explodes.

So, you connect a fan to one of the holes of the tube.  It blows just the right amount of air to generate 15 units of atmospheric pressure inside the tube, which opens it up and allows some air to come out of the second and third hole in the innertube.

Now imagine that you put your mouth on one of the two open holes.  As soon as you do that, you block the flow of air through that hole.  Now, only one of the holes in the innertube is opened.  The fan must immediately reduce the amount of air that it is pushing into the system. Otherwise, the pressure will start to go up dramatically and the tube will explode.

Now imagine that you start sucking air out of the tube from hole that your mouth is on.  When you do that, the pressure inside the tube is going to go down below 15 and the tube is going to collapse.  In order to keep the innertube open, the fan will have to increase its speed just to keep the pressure at 15.  However, you don't need to increase the pressure.  15 units is still enough, but the fan has to work harder, i.e., put out more force, to keep the pressure at 15 since you're sucking air out of the tube while it's working to put air into the tube.

Now, let's say that you reverse course and start blowing into the hole in the innertube.  When you do that, the pressure inside the innertube is going to go up.  As it goes up higher and higher, it will be harder for you to breath into the innertube.  And if you get to 15.5 pressure units, the tube will fail.  Fortunately, our fan at the other end is smart.  As it sees the pressure start to go up above 15, it reduces its effort and lowers the CFM, but keeps the pressure at 15.  In doing so, you can easily breath into the tube, and the pressure remains at 15. 

That's how a CPAP works!  The fan is the CPAP machine.  The hole you put your mouth on is where your mask hits your face.  The third hole is the mask exhaust.  The tube is your airway.
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#74
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
I'm moving on.
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#75
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
Now, this is where BiPap comes in:

Suppose that in addition to keeping the tube open, you also want to make it larger so that it will hold more air.  That's what we do when we breath in.  Our lungs expand and take in more air.  There are two ways to accomplish that.

First, you can physically grab the tube from the outside and stretch it.  As you do that, the inside will expand, the pressure will drop, and the fan will have to work harder to keep the pressure at 15 units.  If the pressure goes below 15 units, the tube will collapse, even though you're stretching it.  As long as the pressure remains at 15 units, the tube will expand as you stretch it and it will fill with air.  That's how lungs normally work.  The chest cavity lifts up, and the lungs fill with air.  The pressure, however, will remain the same.

But, suppose you cannot stretch the tube far enough, and you want to get even more air into the tube (i.e., a person is not breathing deeply enough and you want to increase tidal volume and prevent hypopnea)?  Well, then you can increase the fan speed enough to increase the pressure, and the innertube will start to expand beyond the amount by which you stretched it.  That's what a BiPap machine does with IPAP.  It forces the lungs open without regard to the effort of the chest muscles.

I hope this clarifies things..
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#76
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
(11-19-2017, 05:32 PM)Reznik Wrote: In Bi-level mode, it is accepted that the EPAP is what prevents obstructive events and the pressure support (the difference between EPAP and IPAP) is what helps to prevent central apneas and hypopnea.

What I've read is that the EPAP component is thought to be effective in suppressing frank obstructive apneas, while IPAP primarily acts to prevent obstructive hypopneas, respiratory effort related arousals, and snoring. I suspect this often stated information may be an oversimplification based more in “expert opinion” than in hard data. Or if there are data to support it, I couldn’t find them.  If you have a reference showing otherwise, please share it!

This is a good review of modern device technologies and settings: https://www.ncbi.nlm.nih.gov/pmc/article...po=39.5833

Quote:Because of the delay in detecting the onset of inspiration and delivery of the pressure adjustment, it is common for the inspiratory pressure needed for BiPAP settings to prevent obstruction during early inspiration to be higher than the CPAP pressure needed to prevent the same. For example, a patient requiring CPAP 8, may require BiPAP 10/6 so that a pressure of 8 is reached early enough in the inspiration to keep the airway open.

As you can see, those particular authors aren’t making a distinction between the types of obstructive events that occur due to inadequate positive pressure prior to inspiration and types of obstructive events that occur due to inadequate positive pressure in early inspiration.  It seems that many members here find the same thing: namely that their Resmed expliratory pressure using EPR or BPAP does not have to be quite as high as their prior CPAP pressure to get equivalent prevention of obstructive events including obstructive apneas.
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#77
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
(11-24-2017, 11:01 PM)Reznik Wrote: You're not using a Resmed AirSense 10 machine.  You're using a VPAP machine.  It correctly discloses the EPAP pressure, unlike the AirSense 10 which only displays the IPAP pressure.  I would not expect you to see any difference in the auto-titrated EPAP as you adjust pressure support on the VAUTO.

I'm talking about the IPAP pressure.
Sleepster

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#78
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
(11-25-2017, 07:20 PM)Shin Ryoku Wrote: What I've read is that the EPAP component is thought to be effective in suppressing frank obstructive apneas, while IPAP primarily acts to prevent obstructive hypopneas, respiratory effort related arousals, and snoring.  I suspect this often stated information may be an oversimplification based more in “expert opinion” than in hard data.  Or if there are data to support it, I couldn’t find them.  If you have a reference showing otherwise, please share it!

Hi Shin,

First, thanks for joining the discussion.

Second, I want clarify something here.  I'm not telling you my opinion or "expert opinions."  I'm telling you what the American Academy of Sleep Medicine and the American Academy of Sleep Technologists believe.  The publications that I referenced are the titration protocols that those organizations have published.  So, this isn't my "expert opinion," it is evidence-based science.

You can read the AASM's clinical guidelines here:

https://aasm.org/resources/clinicalguide...040210.pdf

You can reach the AAST's summary of the clinical guidelines here:

https://www.aastweb.org/hubfs/Technical%...6163811483

I've also told you how Resmed and Respironics machines actually work, based upon the contents of their provider guides and other publications that are available to me.  Again, this isn't me telling you what I think.  I'm telling you what Resmed and Respironics appear to think, as evidenced by how their machines actually work today.  

Among other things, the machines appear to respond to central events in a way that isn't currently supported by the AASM/AAST guidelines.  As has been noted, the guidelines do not mention the use of Pressure Support to respond to central apneas.

However, both ResMed and Respironics appear to be using adjustments to Pressure Support in an effort to reduce central apneas, as evidenced by the behavior of their machines.

You can read the ResMED AirCurve 10 ASV Clinical Guide by requesting it by email from Apneaboard.  On Page 4, it explains how that machine increases and decreases IPAP in order to respond to central apneas.  Specifically, it says that the machine "treats central sleep apnea and/or mixed apnea and periodic breathing by automatically adjusting the pressure support (PS) in a defined pressure range to maintain Minute Ventilation at the target."  This makes clear that ResMed thinks that adjusting pressure support is an appropriate response to a central apnea.

Instructions on how to obtain your own copies of the provider guides can be found here:

http://www.apneaboard.com/adjust-cpap-pr...tup-manual

holden4th has jumped in and told us how his DreamStation Auto BiPap appears to respond to central apneas by adjusting IPAP by itself (without adjusting EPAP), although the Provider Guide makes no mention of that behavior.  That evidences that Respironics also believes that adjusting IPAP alone (i.e., changing pressure support) is an appropriate response to a central apnea.

Third, I make absolutely no claim that the AASM, the AAST, ResMed, or Respironics are actually correct on any of these issues.  Science and medicine are constantly evolving, and so it is quite likely that AASM and AAST will change their titration guidelines at some point in the future as more evidence becomes available.

Typically, these guidelines develop after people try various things for several years, and either a consensus develops about what works or what doesn't, or a study comes out proving that something does or does not work.

Once more evidence comes in, the AASM may well take what ResMed and Respironics machines are actually doing, i.e. adjusting pressure support to respond to central apneas, and adopt it as a guideline.  Or they may do just the opposite, and say that it doesn't work.  

The human body is infinitely complex, and so it is not surprising that some individual will not respond in the way that the AASM/AAST protocols suggest, or that those individuals will not respond the way that the Respironics or ResMed machines are programmed to expect humans to respond.

For example, when ResMed introduced the AirCurve 10 ASV, they specifically marketed it for patients who have Cheyne Stokes Respiration caused by heart failure.  During actual usage, however, they found that some people with certain types of heart failure actually died at a greater rate on ASV than they did on conventional BiPap treatment.  As of 2015, ResMed no longer recommends the ASV machine for those patients.  Presumably, they will go back to BiPap treatment, which can also be effective for patients with CSR, though not as effective as ASV machines, as evidenced by the fact that Respironics DreamStation Auto BiPap will adjust Pressure Support in response to central apneas.  You can read the AASM's take on this matter here:

https://aasm.org/special-safety-notice-a...t-failure/
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#79
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
(11-25-2017, 09:44 PM)Sleepster Wrote:
(11-24-2017, 11:01 PM)Reznik Wrote: You're not using a Resmed AirSense 10 machine.  You're using a VPAP machine.  It correctly discloses the EPAP pressure, unlike the AirSense 10 which only displays the IPAP pressure.  I would not expect you to see any difference in the auto-titrated EPAP as you adjust pressure support on the VAUTO.

I'm talking about the IPAP pressure.

Once again, on the VAUTO machine, EPAP and IPAP are locked together.  If one goes up, the other goes up.  You cannot infer from that behavior whether the IPAP is dragging up the EPAP or the other way around.  

But, on the Aircurve 10 ASV, Resmed allows the EPAP and IPAP to adjust independently of one another.  In the provider guide for that device, Resmed makes clear that which conditions IPAP addresses and which conditions EPAP addresses.
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#80
RE: Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??
Here are the titration protocols for Central Sleep Apnea from the AASM..

https://j2vjt3dnbra3ps7ll1clb4q2-wpengin...07/CSA.pdf
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