Effects of too much pressure

Thanks, Snoredog. I'll have to have a look, but I thought the RemStar settling period was both variable and criteria-driven by the algorithm (sequence-detecting respiratory cycles that were deemed "baseline suitable")--- rather than always using the same fixed settling time-frame that would be either hard-coded within the algorithm or even user specified.

Snoredog wrote: Then again if the machine has some sort of settling built-in, they may need to enable it so it actually works because it clearly didn't work in this case. Looks like there may have been a 10-minute settling period (guessing from the graph) at the very start of the session because it ignored several vibratory snores and hypopnea in the very beginning of the session before applying pressure. Respironics should really look at that graph and determine if they have a problem.

I have to disagree with that. The Respironics VS algorithm calls for a 1 cmH2O increase after 3 snores, with less than 30 seconds between each snore, are detected. A closer examination of the graph shows:



There are only 3 snores.

If you run the Training Program placing the events in the exact order in which they appear on cwsanfor's report (VS, VS, H, VS, H, A)(don't put the hypopneas together, or you get an IPAP increase), you get the same response that cwsanfor did. I question whether the time period for the snores is within a minute, certainly looks longer, but what the hey.
SAG

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CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, Hypopnea

StillAnotherGuest wrote:

Snoredog wrote: Then again if the machine has some sort of settling built-in, they may need to enable it so it actually works because it clearly didn't work in this case. Looks like there may have been a 10-minute settling period (guessing from the graph) at the very start of the session because it ignored several vibratory snores and hypopnea in the very beginning of the session before applying pressure. Respironics should really look at that graph and determine if they have a problem.

I have to disagree with that. The Respironics VS algorithm calls for a 1 cmH2O increase after 3 snores, with less than 30 seconds between each snore, are detected. A closer examination of the graph shows:



There are only 3 snores.

If you run the Training Program placing the events in the exact order in which they appear on cwsanfor's report (VS, VS, H, VS, H, A)(don't put the hypopneas together, or you get an IPAP increase), you get the same response that cwsanfor did. I question whether the time period for the snores is within a minute, certainly looks longer, but what the hey.
SAG

The best thing for me to do in this level of discussion is to Stand Back and Let the Big Dogs Eat, but someone asked me to update you on my progress.

I'm very pleased to report:

1) an AHI=0.0 at 14.0/17.5 cm H2O
http://home.earthlink.net/~wallysanford ... 101506.htm

2) an AHI =0.2 (zero apneas, one hyponea, zero snores) at 15.0/18.0 cm (I was titrated at 15.0 cm)
http://home.earthlink.net/~wallysanford ... 102206.htm

3) And similar numbers during that period. Additional details at the link below. When I filter MyEncore to include just the days after the NR event, I note an interesting convergence to zero at 16.0 cm IPAP on the AHI versus Pressure chart. But that chart seems broken, and not recording pressures above 16.0, although EncorePro indicates I've had higher IPAP pressures. Or maybe that chart should be labelled EPAP? Hmm.

Overall, I say both Woo and Hoo. I increasingly believe that the NR reported earlier was an artifact or an outlier. I thank you all sincerely for this very informative dialog. Please continue to talk amongst yourselves.

cwsanfor wrote:Overall, I say both Woo and Hoo. I increasingly believe that the NR reported earlier was an artifact or an outlier. I thank you all sincerely for this very informative dialog. Please continue to talk amongst yourselves.

ROTFL! That's great news, cwsanfor. Thanks for reporting back!

Thank you so much for that update, Cswanfor! I think I'm also favoring artifact/outlier/false-positive at this point as well.

Also a very big CONGRATULATIONS on your excellent treatment results!

-SWS wrote: SAG, if you ever make it to Chi-town for some post-glacial fish, I'll buy you some Miller just for sharing that 420e graph, but I won't go so far as to buy you an Adapt-ASV.

LOL! Actually, I'm even cheaper than that, a Powerade will do just fine (any flavor except Fruit Punch - YUK!). Say, was that your foot I saw sticking out in front of Cheruiyot on Sunday?
SAG

StillAnotherGuest wrote: Say, was that your foot I saw sticking out in front of Cheruiyot on Sunday?

Shhhh!

...Besides, there's not a single shred of jealousy that might be secretly festering on my part.

So what if my wife and I cherish the notion that we're at the absolute pinnacle of human athletic prowess as we perspire through our two-mile "power" walks???

OK, the Bench Evaluation Studies that came out earlier this year demonstrated a bunch of things, not the least of which was that we really don't know exactly how the APAP algorithms actually work. We can get a clue from some of the patents, demonstrations and descriptions, but whether or not the machines use them in the precise manner in which they are described, or if patients respond the way they are supposed to may be another matter. For instance, a 2004 description of the A10 algorithm discussed addressing "open airway" (central) apneas with FOT and cardiac oscillations, and listed a different Time Constant from what seems to be in ResMed APAPs for pressure reduction following the addressing of snoring and flow limitations:

Paraphrased wrote:The procedure, "measure airway conductance using the forced oscillation method" can be implemented using:
(1) If the current pressure is low and FOT scores the airway as closed, then score the airway as closed.
(2) If the current pressure is high and FOT scores the airway as open, then score the airway as open.
(3) Otherwise, score the apnea as of unknown type.

A further possible arrangement is to substitute the `cardiogenic method` for determining airway patency for FOT.

Pressure reduction time constant due to apnea is 20 minutes, to flow limitation is 10 minutes, and to snoring is 10 minutes

but I don't think these apply to the American machines, this patent may be referring to what is in the "AutoSet II Plus".

Anyway, to revisit the A10 algorithm, with a little emphasis on what happens at pressures >10 cmH2O, I offer the following brief, largely stolen from patents:

The ResMed algorithm is suitable for subjects in whom obstructive apneas are controlled at a CPAP pressure of less than 10 cmH2O. This prevents obstructive apneas in the majority of subjects and avoids undesirable pressure increases due to central apneas.

In most patients, apneas decrease as the pressure increases. Because the pressure due to repetitive apneas cannot exceed 10 cmH2O, and most pressure-induced central apneas occur at high pressures (typically above 10 cmH2O), this algorithm will not falsely or needlessly increase pressure in response to most pressure-induced central apneas, thus avoiding the cycle of high pressure leading to central apneas leading to further pressure increase.

Patients exhibiting continued respiratory events may be addressed by the addition of independent pressure increases in response to partial upper airway obstruction indicated by the presence of snoring or flow-limitations. In the majority of subjects, in whom substantial periods of snoring or flow limitation exist prior to any closed airway apneas, the CPAP pressure will increase to a sufficient level to largely eliminate severe partial obstruction, without any apneas of any kind occurring. In those subjects in whom obstructive apneas appear with little or no prior period of partial obstruction, the first few apneas will produce a brisk increase in CPAP pressure as previously discussed, and in general this will provide sufficient partial support to the airway to permit periods of detectable partial obstruction, preventing any further apneas from occurring. Thus, apneas can only cause the CPAP pressure to rise as far as 10 cmH2O, but indicators of partial obstruction can increase the CPAP pressure to 20 cmH2O, which is sufficient to treat the vast majority of subjects.

The "snore threshold" function makes machine response increasingly less aggressive as the pressure increases >10 cmH2O. The "flow limitation threshold" acts in a similar fashion, requiring more severe flow limitation if the pressure is already high or if there is a large leak.

In the absence of events, pressure reduction will occur after 20 minutes of event-free breathing.

While the title of this thread relates to "Too Much Pressure", perhaps a better way to look at it would be "Do You Have Something That Increasing The Pressure Really Doesn't Help, Either."

Towards that end, I offer the following "Another Good Reason Not To Just Buy An APAP And Think You Can Really Do Anything With It If You Really Have No Idea What The Heck You're Trying To Fix." This is an early version of A10, if in fact, there is such a thing, with high pressure limit set at 20 cmH2O:



In 10 words or less, what you have here is a ton of apneic events that are being ignored. And the reason I think that they are being ignored is that they are largely central (CHF/CSR variety instead of CSDB, but that remains to be seen). The only difference between A10 and the 420E downloads is that this time, the pressure didn't go off the wall. But underlying problems still remain significantly undertreated.
Back to our musing, I imagine a way to suspect that "open airway" apneas are being looked at by FOT or cardiac oscillations would be to see if anyone has an AutoScan graph that has a bunch of apneas that directly result in pressure increases, and they know or at least strongly suspect that they have obstructive apneas at pressures >10 cmH2O. However, since pressure increases also occur because of related snoring or flow limitations (in an obstructive apnea, there's usually a lot of associated snoring around it) that wouldn't be a fail-safe method. The point remains, however, that A10 can at least indirectly address OSA at pressures >10 cmH2O.

A side note, does setting the high limit on a machine that uses A10 really make a hill of beans of difference?

In the Good News, Bad News category, yeah, the example above may show how A10 is supposed to respond (i.e., it did the right thing), but on the other hand, we still got a problem.
SAG

SAG wrote:In 10 words or less, what you have here is a ton of apneic events that are being ignored. And the reason I think that they are being ignored is that they are largely central (CHF/CSR variety instead of CSDB, but that remains to be seen).

I don't think A10 has the embedded program logic to ignore any given apnea based on central-apnea criterion. This may very well be a central apnea patient, or this just may well be a "pressure-anomalous" obstructive apnea case. One epedemiologically atypical presentation of obstructive apnea might be a patient entailing these somewhat "A10-unfriendly" combined SDB characteristics: 1) few preliminary snore or flow limitation event signals (preceding apneas), and 2) obstructive apneas requiring resolution pressures above 10 cm. It's impossible to differentiate this patient's etiology from the above graph. PSG time!

But there is no central apnea differentiation in either the A10 algorithm or on those charts. Rather, A10 is refraining from triggering on each of those "unchallenged" apneas simply because delivered pressure already happens to be 10 cm or above. That's the essence of A10, right? The epidemiological premise of A10's design is that it can prevent apneas by triggering or commanding on snores and flow limitations to its heart's content. But A10's epidemiologically-driven design premise restricts it from responsively commanding to apneas if the delivered pressure already happens to be above 10 cm.

So when we see this patient's "unchallenged" apneas, we see apneas that tend to occur while machine pressure is already above 10 cm. This patient doesn't fit A10's epedemiological design premise very well in my opinion. But this anomalous situation is not too different from that of any given well-respected pharmaceutical solution when you think of it. The world's best pharmaceutical solutions tend to each have less than 100% efficacy rates based on clinical trials and epidemiology. From my perspective achieved efficacy will be less than 100% for any APAP algorithm or even xPAP modality. How much necessary modality-to-modality jockying do we see on all these patient message boards? Even "gold-standard" fixed pressure CPAP modality has refugees (admittedly many or perhaps most of those latter modality changes are elective and uneccesary).

But I absolutely agree that this patient is not at all well-suited for A10. Here's a Resmed factory rep describing where A10 was back when it transitioned from the AutoSet-T platform to S7:
http://www.talkaboutsleep.com/sleep-dis ... itchat.htm

I haven't heard about FOT-based impedence detection hitting any of the American APAP models yet. If FOT impedence detection had deployed on any given North American APAP production model, then I think we would have seen much hoopla and dancing on the marketing literature.

SAG wrote:In 10 words or less, what you have here is a ton of apneic events that are being ignored. And the reason I think that they are being ignored is that they are largely central (CHF/CSR variety instead of CSDB, but that remains to be seen).

Well if I can comment on that poo-poo report SAG, in 10 words or less, I'd say:
"the patient has the wrong machine"
(grin)
My guess is it is probably what you are NOT seeing on that report that tells the story, yes the patient probably has CSA/CSR but WHY did the pressure go above 10cm in response to apnea? Very simple. Snores. Snores NOT seen on the report. Resmed says if I see a snore I'm gonna kill it.

A10 says it won't respond to "apnea" above 10cm. Doesn't say it won't continue to respond to snores, FL's or hypopnea (even though it doesn't trigger on hypopnea). But toss in a few snores and it will chase them until it blows the top of your head off, doesn't matter if a few pressure induced centrals get in the way. Then look at the criteria it looks at to determine apnea, it uses 80%, technically not an apnea but a hypopnea, same thing for hypopnea, it uses 40% reduction in flow, technically a flow limitation. But it doesn't trigger on hypopnea only Flow Limitation, Apnea and Snore. That is a mighty nice lookin report

Snoredog wrote:"the patient has the wrong machine"

Absolutely. Whether a PSG reveals that this patient is of central, obstructive, or mixed SDB etiology, this person is a bad fit for A10's epidemiologically-based design premise.

I am extremely interested in hearing how this case progresses. I also hope this person finds suitable therapy. Some patients are not well-treated by any machine. I hope this is simply a case of required modality or model change.

Thanks for posting it, SAG.

-SWS wrote:

Snoredog wrote:"the patient has the wrong machine"

Absolutely. Whether a PSG reveals that this patient is of central, obstructive, or mixed SDB etiology, this person is a bad fit for A10's epidemiologically-based design premise.

I am extremely interested in hearing how this case progresses. I also hope this person finds suitable therapy. Some patients are not well-treated by any machine. I hope this is simply a case of required modality or model change.

Thanks for posting it, SAG.

Looks like he/she had to get up between 5-6 to take a leak, didn't even bother to turn off the machine Why? probably needed some air!

The patient did do much better after therapy hour 8! The patient would have probably been better off just to have set the maximum pressure to like 8cm or 9cm, would have at least kept the oxygen levels up

Can one have problems with too much pressure? What might be the symptoms?
I had a CPAP machine stop working. It could only go to pressure of 15. I was originally set to be 10. After a few years I was snoring through the 10 and adjusted machine myself to where I could sleep. I started snoring through pressure of 14 and even 15, but the machine could go no higher. Then it died, 7 years, worked great. I did another study and told the tech that I snored at 14 on old machine. Their records showed 10 and I admitted to adjusting it myself. The tech was obviously mad and kept saying it was a prescibed setting, blah, blah.. I should never do that... yada yada. The study was for triation and I got a new machine but pressure set at 11. The first night of use was horrible, my uvala swelled up hanging in my throat and choked me the whole next day. I knew this was a symptom of snoring and I could feel the lack of sleep. I knew how to adjust this machine and bumped it up to 14. I still snored through 14, so I bumped it up to 16. A level I could not achieve with older machine. I feel fine. When I start to fall asleep, I get the ears popping effect, which I conclude to be a good pressure for me. Does that sound right? Should I get ears pop, like if hold nose and blow? Is that too much pressure?
I don't need to hear about how I shouldn't diagnose myself and should go see my Doc. I will do that. But in the meantime, I can't sleep at prescribed pressure. Can too much pressure a problem?

[quote="Guest105"]Can one have problems with too much pressure? What might be the symptoms?
I had a CPAP machine stop working. It could only go to pressure of 15. I was originally set to be 10. After a few years I was snoring through the 10 and adjusted machine myself to where I could sleep. I started snoring through pressure of 14 and even 15, but the machine could go no higher. Then it died, 7 years, worked great. I did another study and told the tech that I snored at 14 on old machine. Their records showed 10 and I admitted to adjusting it myself. The tech was obviously mad and kept saying it was a prescibed setting, blah, blah.. I should never do that... yada yada. The study was for triation and I got a new machine but pressure set at 11. The first night of use was horrible, my uvala swelled up hanging in my throat and choked me the whole next day. I knew this was a symptom of snoring and I could feel the lack of sleep. I knew how to adjust this machine and bumped it up to 14. I still snored through 14, so I bumped it up to 16. A level I could not achieve with older machine. I feel fine. When I start to fall asleep, I get the ears popping effect, which I conclude to be a good pressure for me. Does that sound right? Should I get ears pop, like if hold nose and blow? Is that too much pressure?
I don't need to hear about how I shouldn't diagnose myself and should go see my Doc. I will do that. But in the meantime, I can't sleep at prescribed pressure. Can too much pressure a problem?