Question on Pressure - Updated Info.

My sleep study resulted in a CPAP pressure of 13.

The doctor prescribed a 10 minimum for my APAP.

The pressure displayed for the past nine nights is: 15.2 / 17 / 16.6 / 14.6 / 19.2 / 16.2 / 18.8 / 17.6 / 19

I am wondering if these numbers seem to be excessive for my "ideal" 13 prescription pressure from the sleep study. The leak rate for the same period runs from a low reading od 0.18 to a high of 0.46.

I have lifted the mask off my face, during the night, to adjust it when it started to leak and I am wondering if this "free flow" of air would result in the high pressure reading. I am currently using a large mask but should be medium. The new medium should arrive next week.

For what it is worth my wife's sleep study said 9.0 and she had terrible sleep at that pressure. She is now at a average of 11.8 with a AI of .1 to .2 and a HI of 2.3 to 3.0 on a Resmed S8 Autoset Vantage. YMMV.

JRI wrote:My sleep study resulted in a CPAP pressure of 13.

The doctor prescribed a 10 minimum for my APAP.

The pressure displayed for the past nine nights is: 15.2 / 17 / 16.6 / 14.6 / 19.2 / 16.2 / 18.8 / 17.6 / 19

I am wondering if these numbers seem to be excessive for my "ideal" 13 prescription pressure from the sleep study. The leak rate for the same period runs from a low reading od 0.18 to a high of 0.46.

I have lifted the mask off my face, during the night, to adjust it when it started to leak and I am wondering if this "free flow" of air would result in the high pressure reading. I am currently using a large mask but should be medium. The new medium should arrive next week.

If you don't have the software to tell you what's happening during the night, you're "flying blind". In other words, you don't know WHY the pressures are increasing. Since the ResMed Autos use the A10 algorithm and normally don't pursue apneas above the pressure of 10 cm., the reasons for the pressure numbers are quite probably something besides apnea events.

You also didn't say how your your machine is configured......like, the pressure range. And, you didn't report what your AHI numbers were, either.

Yes, mask removal (in any form, while the machine is blowing) will affect the numbers.

Set your machine in CPAP mode at either the minimum pressure your doctor prescribed or what your sleep study pressure indicated (recommended) and then tweak from there. This is yet another example of why beginning users should avoid Auto settings until they determine whether the titrated pressure is correct. In CPAP mode, your LCD figures MIGHT be a little easier to figure out and be more dependable.

Den

Wulfman wrote:Since the ResMed Autos use the A10 algorithm and normally don't pursue apneas above the pressure of 10 cm., the reasons for the pressure numbers are quite probably something besides apnea events.

I'm not sure I understand what you're saying. The machine will deliver pressure within the range of 4 to 20. Why would it not address apneas above 10?

Wulfman wrote:You also didn't say how your your machine is configured......like, the pressure range. And, you didn't report what your AHI numbers were, either.

The minimum pressure is set at 10 and the maximum is 20.
The pressure numbers were: 15.2 / 17 / 16.6 / 14.6 / 19.2 / 16.2 / 18.8 / 17.6 / 19
The Leak numbers were: .40 / .32 / .18 / .42 / .46 / .40 / .32 / .20 / .24
The AHI numbers were: 14.7 / 10.8 / 8.9 / 9.8 / 13.9 / 10.8 / 10 / 13 / 17.2
The AI numbers were: 2.1 / 2.2 / 1.7 / 2.8 / 2.5 / 2.2 / 1.3 / 1 / 2.7
The HI numbers were: 12.6 / 8.6 / 7.2 / 7.0 /11.4/ 8.6 / 8.7 / 12 / 14.5

Wulfman wrote:Yes, mask removal (in any form, while the machine is blowing) will affect the numbers.

This is what I was thinking might be the problem but I wasn't sure if a brief "free flow" would be recorded as the pressure. I believe that the statistics are good overall but was simply concerned about the pressure reading. My post was to solicit opinion on wether or not the pressure reading seemed to be high considering my sleep study result of 13.

[quote"Wulfman"]Set your machine in CPAP mode at either the minimum pressure your doctor prescribed or what your sleep study pressure indicated (recommended) and then tweak from there. This is yet another example of why beginning users should avoid Auto settings until they determine whether the titrated pressure is correct. In CPAP mode, your LCD figures MIGHT be a little easier to figure out and be more dependable.Den[/quote]

As stated previously I was given a large mask, instead of the medium per the ResMed fitting template, and will be getting the medium mask soon. If that does not clear up the problem I may try the CPAP mode per your suggestion.

Go up to the Search line and type in "A10" and start reading. I just did and it shows 20 pages of posts containing that search criteria.

Here's a quote from a moderated chat on TAS (following link). It may be some years old, but the A10 algorithm has apparently not changed in their current machines.

http://www.talkaboutsleep.com/sleep-dis ... itchat.htm

"6. Why does AutoSet Spirit (and AutoSet T™) have the A10 algorithm?

ResMedSimon answers: The A10 algorithm increases pressure in response to Flow Limitation, Snore, and Apnea up to 10cm H2O. Above 10cm H2O, pressure response to Flow Limitation and Snore continues, but there is no response to Apnea. AutoSet Spirit and AutoSet T do not differentiate between obstructive and central apneas. Increasing pressures above 10cm H2O in response to apnea can lead to "runaway" central apneas."


Unfortunately, too many doctors or DMEs don't know diddly squat about the machines they're pushing. Not all APAPs are created equal.

When using a ResMed Auto with a titrated pressure above 10 cm., the person is probably better off using CPAP mode at their titrated pressure.

When you get your new mask, let us know how your numbers look. Right now, they're pretty bad.

Den

Wulfman wrote:When using a ResMed Auto with a titrated pressure above 10 cm., the person is probably better off using CPAP mode at their titrated pressure.

While I personally don't share that particular view of Den's, I agree with two of his other points in this thread: 1) the machine is responding (perhaps even "over-responding" ) to you snores and/or flow-limitations above 10 cm, and 2) you're pretty much flying blind without the software to tell you what's happening.

Another of Den's frequent points on the message board that I happen to agree with, is that some people just do better with straight CPAP pressure rather than dynamically-adjusting APAP pressures.

-SWS wrote:

Wulfman wrote:When using a ResMed Auto with a titrated pressure above 10 cm., the person is probably better off using CPAP mode at their titrated pressure.

While I personally don't share that particular view of Den's, I agree with two of his other points in this thread: 1) the machine is responding (perhaps even "over-responding" ) to you snores and/or flow-limitations above 10 cm, and 2) you're pretty much flying blind without the software to tell you what's happening.

Another of Den's frequent points on the message board that I happen to agree with, is that some people just do better with straight CPAP pressure rather than dynamically-adjusting APAP pressures.

The basis for my logic is that when dealing with "leaking", it can become a runaway with an Auto......and the higher the pressures (and pressure ranges), the worse it can be. Too many new Auto users seem to fall into this conundrum. Too many masks are handed out that don't fit properly, mouth-leaking is a problem with nasal masks and the pressure changes can lead to disturbed sleep.

Other than that, I don't have any problems with Autos......

Edit: After re-reading my own quote, maybe instead of "titrated pressure", I should have said "the pressure that shows the best results". However, I've always believed that a person should at least start out with their titrated pressure before experimenting with others.


Den

I personally think there are an entire variety of things that can go wrong with APAP. And truth be told I was initially very surprised that APAP worked even better for me than CPAP---albeit they both work well.

Rather than go to the trouble of typing, I'll just cite one of ozij's recent posts. This study shows that for most people, Resmed's algorithm works just as well above 10 cm as Respironics'.

ozij wrote:Titration Efficacy of Two Auto-Adjustable Continuous Positive Airway Pressure Devices Using Different Flow Limitation-Based Algorithms
Katrien B. Hertegonne Bart Rombaut Philippe Houtmeyers Georges Van Maele Dirk A. Pevernagie
Respiration 2008;75:48–54

BACKGROUND: Auto-adjustable continuous positive airway pressure devices are widely used in titration procedures to determine therapeutic pressure levels in obstructive sleep apnea patients. However, differences in operational characteristics may influence the effect on the apnea-hypopnea index (AHI). OBJECTIVES: We compared the titration performance of two devices based on detection of inspiratory flow limitation, i.e. the Respironics REMstar Auto (RR) and the ResMed Spirit (RS). METHODS: Fifty obstructive sleep apnea patients were recruited for a double-blind randomized crossover trial. Both devices were employed overnight by means of split-night polysomnography. The primary outcome was the AHI. Secondary outcome measures were the snoring index, pressure profiles and subjective appraisal of sleep quality assessed the morning after the sleep study.

And I personally believe those results.

But again, IMO since each algorithm is unique, I personally believe that algorithm-unique failure patterns are inevitable for each model. So there are very logically going to be some above-10cm failures with the Resmed implementation. But those are the exceptions rather than the rule. And I can just as easily dig up failure-pattern exceptions for the other algorithms too.

But even CPAP has some drawbacks or failures that get nicely served by APAP or other modalities. I personally do much better with APAP or CPAP than BiLevel regarding aerophagia. And there are white papers supporting BiLevel failure patterns (central induction for instance) in a minority of BiLevel cases as well. The old saying "One size does not fit all" applies with xPAP modalities IMO.

-SWS wrote:The old saying "One size does not fit all" applies with xPAP modalities IMO.

My sentiments exactly.

And, repeating my previous statement......

Wulfman wrote:Not all APAPs are created equal.

And, as I've said many times.....
A person needs to determine what works best for them. Just because they have an APAP doesn't mean they have to USE it in a range of pressures if a single pressure works better.


Den

Wulfman wrote:And, repeating my previous statement......

Wulfman wrote:Not all APAPs are created equal.

And, as I've said many times.....
A person needs to determine what works best for them. Just because they have an APAP doesn't mean they have to USE it in a range of pressures if a single pressure works better.

Well, I'll quote it again since I wholeheartedly agree with that, Den. Patent protections require that the algorithms each be very unique to avoid legal infringements. And as you very well point out, that uniqueness can sometimes yield very different treatment results. It occasionally happens.

I am going to weigh in on this "A10 doesn't respond to Apnea over 10 CMs issue" as it is a cause of so much misinformation.

Over 10 CMs, the A10 algorithm responds to signals from the sleeper that indicate an apnea is looming. It looks for the classic pre-cursor signals incl Snores & analyzes flow limitations looking for flattening of the INSP curve that are typical before an OSA event (hypopnea or apnea). If it detects these it raises pressure. No Auto raises pressure when an Apnea is in progress. They all are designed to look for pre-cursor signs and raise pressure in advance in order to pre-empt an apnea THEY DON'T CHANGE PRESSURE ONCE AN APNEA IS IN PROGRESS.

1) Look for signs of an obstructive Apnea
2) Raise pressure if the signs are detected
3) All going well, the apnea was prevented before it could strike

If A10 detects a NO FLOW APNEA without any pre-cursor signals, yes it will ignore it (but it won't ignore any pre-cursor signals).
Autos, when a NO FLOW APNEA occurs, will stop responding whilst the apnea is in progress. Respironics will stop changing pressure if a no-flow (obstructive or central) Apnea is in progress. Respironics also look for pre-cursor signals in order to PRE-EMPT obstructive apneas, but they do go about it slightly differently to how Resmed do.

DSM

Am waiting with 'baited breath' for someone to ask what must be a very obvious question

Seeing no one else has I'll pose it myself ...

Q. If the A10 algorithm won't respond to apneas when over 10 CMs, & DSM says that Autos stop varying pressure when an Apnea is in progress, then what was A10 doing when below 10 CMs and an Apnea occurred ? - why did Resmed say A10 won't respond to apneas over 10 CMs when it seems they don't do anything when one is in progress no matter if under or over 10 CMs ?

DSM

If you understand this then you most likely understand Autos & the difference between Respironics & Resmed's algorithmic approaches

dsm wrote:Am waiting with 'baited breath' for someone to ask what must be a very obvious question

Seeing no one else has I'll pose it myself ...

Q. If the A10 algorithm won't respond to apneas when over 10 CMs, & DSM says that Autos stop varying pressure when an Apnea is in progress, then what was A10 doing when below 10 CMs and an Apnea occurred ? - why did Resmed say A10 won't respond to apneas over 10 CMs when it seems they don't do anything when one is in progress no matter if under or over 10 CMs ?

DSM

If you understand this then you most likely understand Autos & the difference between Respironics & Resmed's algorithmic approaches

I was just going to respond to your previous post when you threw in this monkey wrench. Your defense of the A10 algorithm casts it in a different light than that posted by Wulfman. The point being while it does not and is not designed to respond to an active apnea, it is designed to "predict" onset of the apnea and thereby avoid it.

In response to this post I offer the following from the S8 Auto Set II clinical guide:

An apnea is defined as a greater than 75% decrerase in ventilation. The AutoSet algorithm scores an apnea if the 2-second moving average ventilation drops below 25% of the recent time average (time constant 100 seconds) for at least 10 consecutive seconds. Treatment pressure increases based on the duration of the apnea. The pressure will not rise above 10 cm H2O when an apnea is detected, to prevent an inappropriate response to central apneas. Initial pressure increases are rapid, but the rate of increase diminishes as the pressure approaches 10 cm H2O. When no further apneas are detected, therpy is reduced towards the minimum pressure with a 20-minute time constant

So it seems that the non-response is a safety measure, built in to prevent the overpressure possible in the event the apnea is caused by a central apnea.

JRI wrote: it is designed to "predict" onset of the apnea and thereby avoid it.

Right. That part is done the same way above 10 cm and below 10 cm. This is where the above and below 10 cm difference lies:

JRI citing the Resmed manual wrote: The pressure will not rise above 10 cm H2O when an apnea is detected, to prevent an inappropriate response to central apneas.

So above we can see Resmed trying to prevent apneas above 10 cm, but not directly responding to them as they would have below 10 cm. That response occurs after the apnea in all cases, as dsm pointed out. The idea is to try and prevent subsequent apneas by getting the patient to a hopefully safer pressure zone.

Wulfman wrote:If you don't have the software to tell you what's happening during the night, you're "flying blind". In other words, you don't know WHY the pressures are increasing. Since the ResMed Autos use the A10 algorithm and normally don't pursue apneas above the pressure of 10 cm., the reasons for the pressure numbers are quite probably something besides apnea events.

I can't agree more. I have had a Uvulopalatopharyngoplasty, I have allergies, I mouth breath, I snore, and my mask is the wrong size. There also may be other factors that I am not aware of.

The software and card reader are the next items on my list after the mask. I can say that I do feel better in the morning and despite the statistical data, feel like I am sleeping better. My biggest complaint, at this point, remains the mask fit and leaking.