APAP Does Not Work As Good as BiPap?

Darth VaderLook said Quote:"Tim, if you purchased an APAP and your doctor prescribed a BiPAP then I wonder who would sell you that with that specific prescription in hand. I am sure CPAP.com or any other online seller of xPAP equipment wouldn't do this at the risk of loosing their business and you can bet that a DME wouldn't do this. Rest assured that your doctor is not going to order a straight CPAP, APAP if a BiPAP is required." UNQUOTE

My Doctor was initially only going to prescribe a CPAP becasue he knew that my insurance/DME would only provide that to me. He was then going to prescribe me an APAP after three weeks, which was the requirement of the DME/INsurance companuy to prove I was "Intolerant" of the CPAP.

But I too, already knew some of the ins and outs of the Insurance coverage and I told him I was just going to go ahead and pay for the machine myself after I became frustrated with the DME.

So he wrote the script for an APAP and that's what I bought from cpap.com.

But then I read this post elsewhere about an APAP not properly treating Hypopneas properly. So that's when I posed the question on this forum.

It would seem as though my APAP will do what it needs to do to treat my Apnea just fine. ( Well at least.... so far... )

Tim

SWS,

A good approach and one I look forward to. I think we have the time and patients (pun) to wait eagerly

Your division of analysis is fine by me.

Cheers

DSM

#2 I'll ad a summary of the points later - I plan to use this exchange to create a question list I would like to put to various manufacturers in the hope they will provide resonably detailed answers. I have one early such interview where the speaker was very open & frank about what their Auto of the day could & couldn't do. I am hoping I can use that as the base by which up-to-date answers will be provided.

D

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CPAPopedia Keywords Contained In This Post (Click For Definition): auto

-SWS wrote:DSM, there are a lot of extremely interesting subpoints in this technical discussion that need to be discussed thoroughly. I intend to delve into each one of those as a matter of interesting subject matter in the upcoming weeks. However, for now I wanted to trade some of my own "in a nutshell" observations.
<snip>

SUMMARY
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As 1 discussion point is the following hypothetical:
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1) User has an AUTO & his supplier sent him out the door with it set 4 - 20 (this happens all the time).
2) User's titration on cpap was say 12 (a seemingly typical number)
3) User is sleeping and the the AUTO has already detected some anomalies and it its intelligent way has boosted the CMS to 9
4) At this point the user rolls onto his back just as the machine hit 9cms and then an OSA incident occurs that in our hypothetical would normally have been prevented had he been on cpap of 12

So what I would like to work through is what does the AUTO do regarding this block and how fast ...
a) Can the AUTO clear this block or will the user have done it long before the AUTO gets to a CMS that will overcome the obstruction
b) Can the AUTO respond rapidly and reinflate the airway
c) Does the AUTO have to go far above our suggested 12 cms


Some givens we can work to
i) That the user's flow limitation is not a central
ii) That the user is a regular user & not someone with unusual breathing patters (unusual for xPAP)



Sub points that will emerge: (really just restating your points in a short summary form)
============================

A) The issues of sending people out the door with AUTO set to 4-20 (4-25 in some cases)
- The design theory that should be supporting using settings of 4-20
- The problems that can occur when using 4-20 settings for everyone

B) AUTO's response to an obstructive apnea
- SWS leaning to view that modern AUTO can clear some sudden OSA events (with qualification)
- DSM leaning to view that modern AUTO is not fast enough to respond to sudden OSA events (with qualification)

C) How AUTOs respond to a set of OSA pre-cursor events (snoring, flow limitations, flow volumes)

D) How AUTOs respond to interpreted flow limitations (hypopneas)

E) The issue of why different brands of AUTO can yield quite different results to some people


DSM

dsm wrote:B) AUTO's response to an obstructive apnea
- SWS leaning to view that modern AUTO can clear some sudden OSA events (with qualification)
- DSM leaning to view that modern AUTO is not fast enough to respond to sudden OSA events (with qualification)

The Remstar Auto records data to a resolution of 30 seconds (correct me if I'm wrong). That should be sufficient granularity to study a sample of qualifying events to learn what really happens. If I recall from the Respironics patent application, at 9 minutes (or thereabouts) something special happens, the machine scratches it's head and ponders "is this maybe a central?", and then waits a while. (Sorry, I can't find the PDF document on Derek's website that describes this). This begs an empirical answer, the data is probably sitting in an SQL dataset already on our computers. Now I'm curious.

-Ric

Ric, I think that any APAP data set is too limited in scope to arrive at any empirical conclusion regarding this particular issue. To arrive at the conclusion that the apnea was cleared by an immediate pressure response, a data set of adequate scope would have to also include PSG cortical arousal information. Specifically, a lack of cortical arousal needs to be present throughout the entire duration of the terminated apnea to prove that an immediate pressure increase was responsible for that cleared the apnea.

To arrive at the converse conclusion that an APAP cannot clear any apneas, we would need to verify (from a statistically robust patient sample) that no apneas are ever "pressure cleared" for all the patients in our sample. Again, for this converse conclusion, cortical arousal data would need to be present to support that cortical arousals occurred for all seemingly terminated apneas and were therefore exclusively responsible.

Ric,

IIRC An average apnea lasts less than 20 seconds (I'll dig up my own sleep lab report).

The issue with sudden apneas is how long the person stops breathing before their brain rings the alarm bells & gets them breathing again.

I can hold my breath for about 50 seconds (on my back, in a very relaxed state). I would be interested to hear how long others can hold theirs (not forced, but either like a simulated block or even a flow limitation similar to a central).

So if in our hypothetical, an AUTO takes longer that 30-60 seconds to shift up 3 CMS then the user will have begun breathing on their own.

I guess as you say, if anyone has stats from their machine that show a pressure rise during their sleep, what is the fastest time anyone can come up with for traversing at least 2 cms.

Such rises are going to be caused by (in general ) ...
- pre-cursor events (snoring choking etc:)
- Apnea patterns (a set of Apneas in a sequence)
- Sudden Apneas (changing sleep poition etc:

I would also be interest if any lab rats among us want to try, to see what you have to do while lying down & say after 30 mins of regular breathing, to get your machine to up its pressure by greater than 2 CMS (I use a CMS guage as it is pretty hard to do it & read the results any other way). Looking at the machine readout panel changes the person's position too much.

Best I could do was with a Resmed Spirit - 2 CMS in about 50 secs (IIRC) - once.

Mostly it took minutes to get a 2-3 CMS rise.

Cheers

DSM

According to my Respironics rep, the Remstar Auto will adjust up 1 cm per minute until it detects that hypopneas and apneas are resolved.

Both my Resmed and Respironics reps don't know why anyone would put an upper limit on their APAPs. They said the algorithm in their machines is such that it's not necessary.

This is a very interesting subject. I have access to the clinical specialist from Resmed. If you have any specific questions on the Resmed auto machines, let me know and I'll ask her.

[quote="DME_Guy"]According to my Respironics rep, the Remstar Auto will adjust up 1 cm per minute until it detects that hypopneas and apneas are resolved.

Both my Resmed and Respironics reps don't know why anyone would put an upper limit on their APAPs. They said the algorithm in their machines is such that it's not necessary.

This is a very interesting subject. I have access to the clinical specialist from Resmed. If you have any specific questions on the Resmed auto machines, let me know and I'll ask her.

DSM wrote: The issue with sudden apneas is how long the person stops breathing before their brain rings the alarm bells & gets them breathing again... [snip] So if in our hypothetical, an AUTO takes longer that 30-60 seconds to shift up 3 CMS then the user will have begun breathing on their own.

DSM, I just did a quick Google search only to see apnea durations mentioned as long as two or three minutes. I don't think that's the upper limit either. However, even these documented apneas of three minute duration imply that it took three minutes in these cases before the cortical arousal process resulted in restored respiration.

How long it takes an APAP to rise 1, 2, or 3 cm cannot definitively answer whether comparatively lighter apneas will fail to be cleared---if the APAP's pressure at that moment of apnea-trigger happens to be within only a half a cm or even a full cm of clearing the airway. Again, I view that the algorithm's precursor-based proactive routines strive for (yet don't always succeed) to place that patient within pressure "striking distance" of clearing many apneas. An example of proactive and responsive routines working hand-in-hand---very heavily leveraged toward proactive pressures.

Thank you DME-guy! We would love to take you up on your offer with our questions. Thank you DSM, Ric, et al for a great discussion!

Ric, here is the link for the US patent document (in pdf format) for the Respironics Auto:

http://lewiston.mit.edu/sleep/Autopatent.pdf

Correct me if I'm wrong but I think that is what you are looking for. You have to be careful with that though as it's description of operation may have changed (ie. any changes to the algorithm will not appear in this document and may affect total operation of the machine).

To DSM:

If you are planning on studying the workings of the Auto you need to get a copy of the latest algorithm or your efforts will be for nothing. Unless you have the equipment to download the 'C' program that is embedded in the microprocessor you will need to get it from Respironics. Unfortunately, I don't think they will be giving that information out any time soon. -SWS is also correct when he states:

Ric, I think that any APAP data set is too limited in scope to arrive at any empirical conclusion regarding this particular issue. To arrive at the conclusion that the apnea was cleared by an immediate pressure response, a data set of adequate scope would have to also include PSG cortical arousal information. Specifically, a lack of cortical arousal needs to be present throughout the entire duration of the terminated apnea to prove that an immediate pressure increase was responsible for that cleared the apnea.

I do want to commend you guys for taking on this task. When and where possible I will help you with any technical knowledge that I can share with you. I do have a couple of comments on your hypothetical discussion but I will post those later.

-SWS wrote:

DSM wrote: The issue with sudden apneas is how long the person stops breathing before their brain rings the alarm bells & gets them breathing again... [snip] So if in our hypothetical, an AUTO takes longer that 30-60 seconds to shift up 3 CMS then the user will have begun breathing on their own.

DSM, I just did a quick Google search only to see apnea durations mentioned as long as two or three minutes. I don't think that's the upper limit either. However, even these documented apneas of three minute duration imply that it took three minutes in these cases before the cortical arousal process resulted in restored respiration.

How long it takes an APAP to rise 1, 2, or 3 cm cannot definitively answer whether comparatively lighter apneas will fail to be cleared---if the APAP's pressure at that moment of apnea-trigger happens to be within only a half a cm or even a full cm of clearing the airway. Again, I view that the algorithm's precursor-based proactive routines strive for (yet don't always succeed) to place that patient within pressure "striking distance" of clearing many apneas. An example of proactive and responsive routines working hand-in-hand---very heavily leveraged toward proactive pressures.

Thank you DME-guy! We would love to take you up on your offer with our questions. Thank you DSM, Ric, et al for a great discussion!

DME_Guy posts:

Both my Resmed and Respironics reps don't know why anyone would put an upper limit on their APAPs. They said the algorithm in their machines is such that it's not necessary.

My understanding of why an upper limit is required is due to mask leakage. If the mask does have leakage beyond the limit set out in the algorithm, it will place dashes in the display and top out the pressure level. By placing an upper limit on the pressure you restrict the runaway condition to that level. There may be other conditions as well that would suggest placing an upper limit on the pressure setting.

It is also my understanding that once 8cms has been reached a flag if you will, is set and the microprocessor makes adjustments to the pressure in half cm levels but will adjust up 3 cm total (to a level of 11cm in this case)to try and clear the apnea. If no noticeable change is detected it will flag this as a central and reduce the pressure down 2 cm where it sits for a period. This is exactly the reason for the 3cm below the patients titrated level so that the apnea can be cleared and not flagged as a central before hand. That is my interpretation of the algorithm. You can correct me if you think I'm wrong. This information can be found starting on page 10 of the pdf file link I provided in an earlier post.

DSM wrote:The duration of an obstrction certainly plays a key role in what an AUTO can do. Am interested in any info on durations. Also as you say if the AUTO is within .5 or there abouts it is better able to respond.

Yes, DSM. I agree. However, how long it happens to take for an APAP to increment 1, 2, or 3 cm says nothing of those apneas getting cleared in a short time window by less pressure. So the 1, 2, or 3 cm time frame question potentially leaves out some if not many apnea-clearing scenarios.

On kind of a funny note it occurred to me that there's an excellent chance we even concur on how an APAP responds to what you refer to as "sudden apneas". To say "an APAP does clear apneas, but with exceptions" versus "an APAP does not clear apneas, yet with exceptions" is much like that proverbial issue regarding whether that glass of water is half empty or half full. Those latter two contentions initially sound contrary, yet they describe the same condition.

I must go. All this typing leaves me half worn out. The good news is I'm half energized.

Darth Vader Look wrote:
<snip>
This information can be found starting on page 10 of the pdf file link I provided in an earlier post.
<snip>

DVL,

This is indeed interesting info but I can't find the link or doc you refer to can you repost tks.

Also another reason for the upper limit is the fact that at least a couple of brands of AUTO will do 'runaways' - I have had this happen myself on 2 occasions. This is where machine goes to its max setting & stays there for some while. I have read reports here from others, of some AUTOs staying at max until stopped by the user.

DSM

-SWS wrote:

DSM wrote: <snip>
To say "an APAP does clear apneas, but with exceptions" versus "an APAP does not clear apneas, yet with exceptions" is much like that proverbial issue regarding whether that glass of water is half empty or half full. Those latter two contentions initially sound contrary, yet they describe the same condition.

SWS,

That registered with me too & I smiled to myself (after I had posted it).

All along we have both been saying that an AUTO is designed to pre-empt OSA events.

The only divergence I still percieve is what type of blockages an AUTO can 'clear' and this really can mean prempt depending on the nature & stage of the 'cleared' block (within a sequence of pre-cursor events).

I think we have both said that some sudden apneas won't be cleared (due to time to get to needed CMS).

The info unfolding is really helping understand this area & its subtlties (ceratinly for me).

DSM