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APAP Discussion
#21
RE: [split] APAP Discussion
These are the plateaus I'm referring to. My machines consistently raise treatment pressure in the presence of these (note the increase in the pressure graph) and I'm assuming it is in response to them (as these pressure increases occur well removed from any events). I could be wrong, but my understanding is that these plateaus represent a pause in flow during inhale (about mid-way) rather than a pause between inhale and exhale. I have rationalized this as representing a limitation in flow during inhale causing a cessation of the inhale (at the plateau) which leads to greater respiratory effort in order to resume the inhalation (the slope in the leading edge between the plateau and crest).

It is my understanding (I could be wrong here too) that this pattern is seen as in indicator of flow limitation that is used as a signal in the advanced algorithms to initiate a pressure increase (among other signals such as vibratory patterns). I think this is one of a few ways the advanced algorithms try to prevent events (obstructive A/H) rather than just responding to them. I also think this is one reason why the AutoSet algorithm is sometimes accused of "running away" with the pressure (a bad rap in my opinion, except possibly for the very few people who actually have RAS), as the algorithm reportedly attempts to defeat these FL patterns more aggressively than other advanced algorithms. I'm pretty sure that ResMed sees these patterns as being disruptive to sleep even in the absence of what would technically be called events. In their papers and also in the excellent SDB video Zonk has linked a few times (one of the sources I've used to draw the conclusions I've made above) they often seem to indicate that these plateaus stimulate respiratory effort and possibly a certain level of arousal as well as indicating a progression toward an actual event in the event an arousal state sufficient to normalize breathing is not reached.

It could be wrong, but that's my incomplete understanding of it.
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#22
RE: [split] APAP Discussion
The "plateaus" first mentioned by jgjones1972 are NOT part of the inspiration (inhalation). Those "plateaus" are just a normal pause in airflow between the end of the exhalation and the start of the next inhalation. They are NOT flow limitations and they are NOT the reason the S9 is increasing the pressure on this stretch of breathing.

Flow limitations are changes to the normal shape of the inspiratory part of the wave flow. While I can't find anything quickly on Resmed's web pages about how the S9 scores flow limitations, PR does have this information on its web pages at http://sleepapnea.respironics.com/techno...ation.aspx :
Quote:Flow Limitation
While other devices typically respond only to flatness and shape, our auto algorithm analyzes changes in flatness, roundness, peak and shape. This precise recognition of unique patient flow patterns is the reason why the REMstar Auto reacts better than any other device on the market.

More technical information about what flow limitations look like in the wave form have been published in a number of medical journals over the years. The following chart of typical flow waves indicating flow limitations of various forms is from Chest Journal and the original paper ("Performance of Nasal Prongs in Sleep Studies: Spectrum of Flow-Related Events") is available on line at http://journal.publications.chestnet.org...id=1079501
The figure is Fig. 2 in the article.
[Image: flow_limitation_images.jpg]

Here's another chart of just the inspiration part of flow waves demonstrating flow limitations can be found in " Analysis of Inspiratory Flow Shapes in Patients With Partial Upper-Airway Obstruction During Sleep" also published in Chest Journal and available at http://journal.publications.chestnet.org...id=1079416
[Image: MoreFlowLimitations.jpg]
On this chart, Type 1 is the "normal" shape for an inhalation. The authors include a table titled Table 4. Characteristics and Suggested Interpretation of the Various Inspiratory Waveforms if you are interested in the authors interpretation of the other wave forms on this table.

Now to get back to jgjones1972's particular example of a breath sequence where his S9 decided to increase the pressure even though there were no OAs or Hs to be found. As jgjones1972 says, a picture is worth a thousand words. I've taken the image posted by jgjones1972 and have marked it up just a bit:

[Image: Plateaus_zps0d16fe2d.jpg]

In the edited image I have circled the inhalations (the inspiratory parts) of the wave flow. Now recall that flow limitations are based on the shape of the inspiration part of the wave flow. When we compare this series of breaths to the two previous charts, we see that many of these inhalations show some of the classic "flow limitation" shapes in those inhalations. Some of the more obvious changes in shape from a normal inhalation include:
  • the double peaks on the first and last circled inhalations in this set of data.
  • the sharp triangular "peak" followed by an almost linear decrease that is present in almost all of the circled inhalations as opposed to a more "rounded" normal inhalation.
  • a "chair" pattern that is subtly present in circled breaths #2, 4, 5, and 12 (especially 12) where there is a (very) short plateau during the inhalation before the large, normal exhale dip starts.

This series of breaths is clearly demonstrating enough characteristics of "flow limitations" that an S9 AutoSet or a PR System One Auto would definitely be increasing the pressure during this time---if the pressure is not already at max pressure. And sure enought, if we look very closely at the pressure curve, we can see the beginning of the pressure increase about halfway between 04:02:40 and 04:02:50.



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#23
RE: [split] APAP Discussion
(12-14-2013, 01:26 PM)jgjones1972 Wrote: These are the plateaus I'm referring to. My machines consistently raise treatment pressure in the presence of these (note the increase in the pressure graph) and I'm assuming it is in response to them (as these pressure increases occur well removed from any events). I could be wrong, but my understanding is that these plateaus represent a pause in flow during inhale (about mid-way) rather than a pause between inhale and exhale.
The only plateaus I see are the normal slight pause between the end of the active part of the exhalation and the beginning of the active part of the inhalation. Those plateaus are NOT what's triggering the pressure increase. What's triggering the pressure increase is the ragged shape of the inhalations themselves. In this stretch they have all the hallmarks of flow limited inhalations: they are not smooth round humps---instead they have jagged corners, flat sloping edges, and sometimes two peaks. It's the shape of these inhalations that are triggering the pressure increase.

Quote:I have rationalized this as representing a limitation in flow during inhale causing a cessation of the inhale (at the plateau) which leads to greater respiratory effort in order to resume the inhalation (the slope in the leading edge between the plateau and crest).
No. The problem is NOT the momentary pause---that's a perfectly normal part of sleep breathing. The flow limitation is showing up in the inhalation itself: The airway is just barely compromised---not enough to warrant being flagged as a hypopnea, but it is requiring extra effort to get the air in through the narrowed airway. And it's that extra effort that shows up in ragged shape of the inhalations.

Quote:It is my understanding (I could be wrong here too) that this pattern is seen as in indicator of flow limitation that is used as a signal in the advanced algorithms to initiate a pressure increase (among other signals such as vibratory patterns). I think this is one of a few ways the advanced algorithms try to prevent events (obstructive A/H) rather than just responding to them.
This breath sequence does show evidence of flow limitation, but it is the ragged shape of the inhalations themselves and NOT the pauses between the exhale and the inhale that are evidence of the flow limitation and it is the ragged shape of the inhalations that is triggering the pressure increase.


Quote:I also think this is one reason why the AutoSet algorithm is sometimes accused of "running away" with the pressure (a bad rap in my opinion, except possibly for the very few people who actually have RAS), as the algorithm reportedly attempts to defeat these FL patterns more aggressively than other advanced algorithms.
Resmed's algorithm is far more aggressive than the PR algorithm in treating FLs. And that can contribute to some people complaining that the AutoSet has a tendency to have the pressure "run away."

Quote:I'm pretty sure that ResMed sees these patterns as being disruptive to sleep even in the absence of what would technically be called events.
Yes, there is some evidence that FL can be disruptive to some people's sleep. In fact the whole problem that folks with UARS have is that the flow limitations tend to trigger EEG arousals well before a clinical H can be scored.

And so it's all well and good to try to eliminate the FL. But---and this is an important but: Some people find those rather rapid and significant increases in pressure more disturbing to their sleep than the FL themselves. Sharp increases in pressure can and do wake some people up. And if you're prone to aerophagia all that extra pressure to eliminate the last of the FL can increase the aerophagia, which can increase the arousals, and lead to even more swallowing. Sharp significant increases in pressure can also lead to additional problems with mask leaks and also under some circumstances trigger mouth breathing in a person who otherwise breathes exclusively through their nose. And those things can cause problems with both the quality of the therapy and the quality of the sleep. And finally there's the fact that about 10% of PAPers do have some problems with pressure induced centrals.

So when a CPAP maker is designing an auto algorithm, how they decide to respond to FL is almost by definition a series of compromises. You want to increase the pressure (at least some) and see if that helps stabilize the shape of the inhalations, but you don't want the pressure increase to be so rapid and so great as to cause as many problems as it solves for the vast majority of users.

I think that's part of why PR has taken a very different route in dealing with FL. The PR machines do respond to FL by increasing the pressure by 1 cm and then they wait for about a minute, if I recall correctly. If the breathing stabilizes in that minute, there's no further increase. If more FL are detected, the machine raises the pressure another 1cm and waits another minute. It's slower to respond, but that means the pressure increase by itself is less likely to wake up or arouse the user. And PR also attempts to proactively find the best pressure even before the inhalations in the wave flow have become ragged enough to trigger a FL flag. And that proactive "search" algorithm also prevents the PR System One from lowering the pressure too far, too quickly.
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#24
RE: [split] APAP Discussion
I stand corrected. It makes much more sense now, as well as what Sleepster was saying.

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#25
RE: [split] APAP Discussion
I have a Respironics Bi-pap Auto Bi-flex with 6-16 pressure settings. The Bi-flex setting is 3. In looking at my Sleepyhead data, I can see that my inhale Pressure is sometimes as high as 10 while my exhale is always a constant 6. I may be getting too picky here, since I would very much like to more fully understand the treatment, but I can only seem to grasp a somewhat vague, fragmented, understanding of all this. I do notice that when I begin each night, it seems that my inhale pressure is inadequate. Not enough to keep me awake, but it still seems that I am sucking in air, and that doesn't seem right.

On the exhale side of things, I notice that in the last two weeks (new equipment) most of my inhale pressures are graphically "spiked" 15 minute periods, and there has been only one period of sustained (2+ hours) higher exhale pressure. Not a problem, I suppose, but puzzling. I also notice that the pattern of Event Breakdown Statistics varies greatly from day to day.

So what does this mean, if anything?

Phil

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#26
RE: [split] APAP Discussion
(12-14-2013, 06:45 PM)pdeli Wrote: I have a Respironics Bi-pap Auto Bi-flex with 6-16 pressure settings. The Bi-flex setting is 3. In looking at my Sleepyhead data, I can see that my inhale Pressure is sometimes as high as 10 while my exhale is always a constant 6.
Some clarification is needed here.

It's clear that your minimum EPAP = 6 and your maximum IPAP = 16. There are one or two other settings that we need to know about in order to fully understand how your machine is going to behave during the night.

On bi-level machines, the pressure support (PS) is defined to be the difference between IPAP and the EPAP. In other words, PS = IPAP - EPAP. On the PR System One BiPAPs, the PS is allowed to vary based on the PS settings that are set inside the clinical set up menu.

If you have a newer PR Series 60 System One BiPAP Auto, we need to know what your minimum PS and maximum PS settings are. These settings control how far apart the IPAP and EPAP can be from each other.

If you have the older PR Series 50 System One BiPAP Auto, there won't be a minimum PS setting, but there will be a PS setting. The minimum PS = 2 on the Series 50 machines and the PS setting gives the maximum PS setting.

Some things to keep in mind about the PR BiPAP Auto machines: The PR BiPAP Auto algorithm is split between the things that affect the IPAP pressure and the EPAP pressure. The short version of how things work on the PR BiPAPs is this:

EPAP is increased only when the machine detects
  • a clusters of two or more OAs (A cluster of events are two or more events that occur within about 5 minutes of each other.)
  • a cluster of events made up of both OAs and Hs.
  • snoring
  • the IPAP needs to be increased and the current PS = maximum PS setting.

IPAP is increased when the machine detects
  • a cluster of two or more Flow Limitations
  • a cluster of two or more RERAs
  • a cluster of two or more H's
  • the proactive "search" algorithm's test increase of IPAP pressure results in an improvement in the shape of the inhalations in the wave flow
  • the EPAP needs to be increased and the current PS = minimum PS setting.

NOTE: The Auto algorithm on the Resmed S9 VPAP Auto is very different. On the Resmed VPAP Auto, the IPAP and EPAP pressures are increased by the same amount in response to any event that triggers a pressure increase. In other words, the PS = IPAP - EPAP is a fixed number and does not vary on S9 VPAP. The PS is set in the clinical menu, but once it's set, at any point during the night, IPAP = EPAP + PS.


Quote:I may be getting too picky here, since I would very much like to more fully understand the treatment, but I can only seem to grasp a somewhat vague, fragmented, understanding of all this. I do notice that when I begin each night, it seems that my inhale pressure is inadequate. Not enough to keep me awake, but it still seems that I am sucking in air, and that doesn't seem right.
Do you know what your starting IPAP pressure is???

Since your min EPAP = 6, your starting IPAP should be equal to 6+minPS. If you are using a Series 60 System One BiPAP, the minPS is probably set to something between 0cm and 4cm. You can increase the starting IPAP pressure by increasing the minPS setting. But if you are using the Series 50 BiPAP Auto, your starting IPAP will be 6+2 = 8cm, and the only way to increase the starting IPAP is to increase the min EPAP.

Quote:On the exhale side of things, I notice that in the last two weeks (new equipment) most of my inhale pressures are graphically "spiked" 15 minute periods, and there has been only one period of sustained (2+ hours) higher exhale pressure. Not a problem, I suppose, but puzzling.
If the machine is NOT scoring a lot of snoring and the recorded OAs are isolated---i.e. pretty far away from other OAs and Hs, then that EPAP line is going to sit at your min EPAP regardless of what the IPAP graph is doing---unless you happen to reach a point where IPAP - EPAP = maxPS and IPAP needs to be increased. If you post the wave flow, event, and pressure curves that show the period of sustained higher exhale pressure along with the 15-20 minutes before the EPAP pressure was increased, I'll be happy to look at it and see if I can tell what triggered the EPAP increase and why it stayed elevated as long as it did.

But on the inhalation side of things, IPAP curve is going to have some real variation in it even if there are very few events recorded because of the PR proactive "search" algorithm that is applied only to the IPAP pressure in the System One BiPAP Auto algorithm. Even if absolutely NOTHING is going on in your breathing, the "search" algorithm will periodically kick in and you'll see a test increase of 2cm in IPAP pressure followed by a decrease back down to the current "baseline" IPAP pressure. In other words, the IPAP curve will have a sawtooth appearance to it when there's no evidence of sleep disordered breathing going on in the wave flow. And from your description, that may be what you are noticing in your IPAP curve. Again, if you post a picture of your typical IPAP data, I'll be happy to look at it and determine whether the "spikes" are just the test pressure increases in the "search" algorithm being applied to the IPAP pressure.

Quote:I also notice that the pattern of Event Breakdown Statistics varies greatly from day to day.
Our sleep is not the same each night and our (untreated) OSA varies from night to night. Hence there are going to be some nights where the machine's Auto algorithm may have a more difficult time prenting almost all events. And then there's the fact that on some nights we have more wake after sleep onset (WASO) time and whenever there's a lot of WASO, there's the possibility that the AHI will be different (possibly very different) from a night where you sleep soundly. The reason why is that wake breathing is very different from sleep breathing and there are patterns in normal wake breathing that can fool a machine into scoring "false" events.

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#27
RE: [split] APAP Discussion
(12-14-2013, 06:45 PM)pdeli Wrote: I have a Respironics Bi-pap Auto Bi-flex with 6-16 pressure settings.

Do you have a BiPAP or a REMstar?

Sleepster

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#28
RE: [split] APAP Discussion
(12-15-2013, 12:22 AM)Sleepster Wrote:
(12-14-2013, 06:45 PM)pdeli Wrote: I have a Respironics Bi-pap Auto Bi-flex with 6-16 pressure settings.

Do you have a BiPAP or a REMstar?
Do you know if you a Philips Resprionics Series 60 System One BiPAP Auto or a Philips Resprionics Series 50 System One BiPAP Auto? If your machine is less than 3 years old, it will be one of these two. If you have an integrated heated hose, you've got the Series 60 machine.

If you are unsure, you can take the humidifier tank out of the humidifier unit and turn everything over and look for the model number. It will likely be something like: DS750S or DS760S. The letters are not as important as that three digit number in the middle. If the middle digit is a 6, you've to a Series 60 System One BiPAP Auto. If it's a 5, you've got a Series 50 System One BiPAP Auto.

If your machine was manufactured before 2009, then you probably have a Respironics M-Series BiPAP Auto.

And can you tell me what the PS setting or settings are? That's an important part of describing your pressure settings when using a BiPAP.
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#29
RE: [split] APAP Discussion

Robysue,

Thanks for your detailed response. Let me see if I can sort through all this.

- Other Settings : the bottom of my (month old) machine says "760P". The humidifier says "D86HFLG" and they both say "IP22" as well. Does that help?

- Min/Max PS: is this the 6-16 pressure range that I mentioned?

- Starting IP pressure: that would be 6 (as is the starting EP) and they both remain at 6 for at least an hour or more. In fact, 6 seems to generally be the night long default. It seems to me that there is some sort of sensitivity issue here that delays the machine from going into the prescribed 6-16 range.

- Setting the starting IP: this isn't something that I can do, is it?

I'm not sure that I covered everything, but I think so.

As an aside, I emailed the Doc last week (who I've never actually met) about the apparent delay in the pressure response and have not heard back from him. That's kind of unusual, but he may be tired of me bugging him with questions. It took a year before I convinced him to get me a Bi-Pap, and so now I have a C-Pap and a Bi-Pap.

Phil On



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#30
RE: [split] APAP Discussion
(12-15-2013, 12:42 PM)pdeli Wrote: - Other Settings : the bottom of my (month old) machine says "760P". The humidifier says "D86HFLG" and they both say "IP22" as well. Does that help?
You have a PR System One REMStar 60 Series BiPAP Auto with Bi-Flex.

Quote:- Min/Max PS: is this the 6-16 pressure range that I mentioned?

- Starting IP pressure: that would be 6 (as is the starting EP) and they both remain at 6 for at least an hour or more. In fact, 6 seems to generally be the night long default. It seems to me that there is some sort of sensitivity issue here that delays the machine from going into the prescribed 6-16 range.
Sounds like min PS = 0. That would encourage the machine to keep both EPAP and IPAP as close to 6 as possible all night long. Also sounds like the ramp may be on since you say that there is "some sort of sensitivity issue here that delays the machine from going into the prescribed 6-16 range". When you first put the mask on and start using it, the LCD should be showing two numbers, one on inhale and one on exhale. The numbers will be labeled IPAP and EPAP. Can you tell me what those numbers are when you first mask up and turn the machine on?

Quote:- Setting the starting IP: this isn't something that I can do, is it?
Depends on how comfortable you are with the idea of changing your own pressures. The DME will tell you, "You can't do that." If you get the Clinician's Manual from apneaboard, you can get into the clinical set up menu and change the min PS setting which will change your starting IPAP pressure. All you need to know is:

Starting IPAP = min EPAP + min PS

Whether your doc will fuss at you depends on the doc. Some docs will whip you with a wet noodle and say, "You can't do that". Others will be realistic and say something more along the lines of "Check with us before you change the pressures," or "Don't make any really large changes without getting the doc's approval."

Quote:It took a year before I convinced him to get me a Bi-Pap, and so now I have a C-Pap and a Bi-Pap.
Do you know what your CPAP settings were, including the Flex or EPR setting? That might give some insight into what a good starting point for setting the min PS setting on your BiPAP


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