Question on Pressure - Updated Info.

[dsm]

dsm, what in the world is a "no flow apnea"?
Your posts above are the first time I've run into that term.
An apnea is an apnea = non breathing. Air does not flow during an apnea.

An apnea can be obstructive= air cannot come in or out; or open airway = nothing obstructing the flow, but the brain is not sending instructions breathe.

ReMed assume that a "frank apnea" (ResMed term) above 10 cms has a great probability of being an open airway apnea, and it will not raise pressure when it sees that. It also assumes its response to flow limitations and snoring will create a pressure environment in which frank obstructive apnea will not occur. The assumption holds true for many, but not all.

All autos attempt to distinguish open airway apneas from obstructive apneas. They go about it in different ways, and they all err for lack or enough data.
The question is always: do I fall within this machine's errror group, or do I fall withing that machines error group?

O.

Ozij

I missed this before.

Ozij I am sure we agree that Apnea as used repeatedly here & by vendors can mean a lot of different things - it may technically mean 'no-flow' but common use does not back that up. You introduced (in this thread) 'Frank Apnea', that is a term I haven't seen often not many vendors use it. I used the term 'no-flow' apnea - which is more descriptive ?. What I was trying to convey was at least an apnea that is flow reduced enough to be accepted as an apnea by both Resmed and Respironics & again we both know that each vendor will score their idea of an 'apnea' differently & none that I know of only score 'apnea' as an absolute zero flow.

You really raise a very interesting aspect of meanings of words. I would bet that most people who have heard of sleep apnea, and are told they have an AHI of say 40, will call all those events 'apneas' and would not understand that there are different types of events falling loosely under the umbrella term apnea & to compound that confusion, different vendors and different interested organizations will have different definitions ..

We can have
- apneas - zero-flow - technically the correct term as you have pointed out
- apneas - as scored by Resmed in their data (75% reduced flow ?)
- apneas - as scored by Respironics in their data (80% reduced flow)
- apneas - as scored by any other vendor's software
- hypopneas - which are just a little less than an apnea based on duration & a broader definition of reduced flow. But again with multiple definitions by different vendors and organizations.

Do you agree that most newcomers to this discussion group have to go through a lot of confusion before they eventually begin to grasp the mess of definitions apnea appears to cover ? - I am in no doubt !.

So when anyone of us adds repeatedly to that confusion we are not helping. Because, that is exactly how I feel about the confusing statement "A10 does not respond to Apneas over 10 CMs". Again & again we see people misinterpret that to mean that Resmed A10 does nothing about OSA over 10 CMs and that is because the statement is out of context and that most newcomers do not yet know the variety of different event types that in their minds are all just 'apneas' .

It gets really complicated when one of us is saying apnea but in the mind is meaning no-flow & is debating with someone else who says apnea & means a partial obstruction (partial apnea).

I know this confusion will go on because when we get into these debates the terms as so slippery they won't stay still

Cheers

DSM

Why don't we start a contest, see how many definitions for apnea scoring that we can find I believe it would be very informative

[Husky Lover]

This is all very interesting. I'm learning some limitations on my new ResMed S8 Autoset II. I'm not getting my AHI's below 5 often enough. Correct me if I'm wrong, but whether obstructive or central apneas, isn't oxygen saturation what we are really interested in? If so, why isn't more emphasis placed on recording that during the course of PAP treatment?

[dsm]

Following on this issue of confused meanings ...

The reason it is important to understand the real world difference between a zero-flow (no-flow) apnea and a partial apnea (as scored by Resmed & Respironics etc:) is because each has its own importance.

Most of us use Positive Airway Pressure to splint our airway open. The titration is intended to find for each person where that splinting effect does the most good vs introduces other problems (i.e. mask management problems & possible Complex Apnea (CompSA adds centrals triggered by the cpap therapy)). The intention of titration is to find the *lowest* pressure the lab is satisfied with that reduces the persons scoring of 'events'. Some labs believe they only need to titrate to the point they eliminate or greatly reduce apneas & hypopneas. Other labs argue they should titrate to the point of eliminating apneas, hypopneas and even flow limitations. Bilvel therapy appears to allow a higher level of 'tuning' to these latter labs.

The magic 10 CMs is considered by some to be the point where most airways are normally held open.

If I am the xpap machine & have some intelligence I can try to figure out a few things....

1) If I know your airway is open but there is ZERO FLOW (vs a partial apnea) then I can reasonably confidently say you are having a central apnea
- As Ozij has explained many times, the Sandman listens for cardiac oscillations & if heard says the airway is open
- Weinmann & Resmed experimented with a technique called FOT which sends a burst of oscillating air down the airline (around 3k to 5k hertz),
by monitoring the response they were often able to say the airway is open or closed, but in recent years FOT seems to have been dropped
- Weinmann now use a different technique they label OPP & they claim this allows them to make the right decision. Am not clear yet as to how
this OPP technique works but Weinmann obviously see it as better than the FOT approach.

2) If the airway is open & there is something like 20-25 % flow (of a normal breathing flow) and it lasts longer than 10 secs, then I can consider this
is probably obstructive, but would really need a signature (flow-lims turning into hypopneas turning into a partial apnea and or snores) any groups
of these events can provide a signature that labels the apnea as obstructive. A central is a declining flow, usually with little to no flattening of
the inspiration curve (as being sampled over prior breaths).

A major goal of the Auto designer is to accurately identify the difference between obstructions & centrals. Within the profession, RTs will talk
about partial centrals & partial apneas & as we know the technical definition of an apnea is zero-flow, but as we also no, that is not how vendors
score apneas on their autos. So we have to accept that there are not clear cut definitions of these.

The need for differentiation between central & obstruction is very important as to what action to take. If we have an obstruction & no evidence of centrals, it is a pretty safe bet we can raise the pressure, this can be in steady steps, most Autos raise in 0.5 or 1.0 CMs steps & 'sniff the signals' before raising again. They raise pressure in anticipation of an apnea on the basis they are seeing OSA signatures in the respiration signals been monitored.

NO Auto will adjust pressure whilst an apnea is being scored (apneas as defined by Resmed's 75% reduced flow & Respironics 80% reduced flow &
both using 10 secs as min duration * ) - they wait until after the apnea & as we know Resmed will ignore a scored apnea if pressure has already gone
over the magic 10 CMs and does so on the basis that the majority of users have their airway held open at that pressure. And as we now know, Resmed and Respironics (and the others) continually look for the signatures of obstructive apneas and adjust pressure to pre-empt a scored apnea.

It is worth pointing out that when a central is occurring, raising pressure will normally not get the sleeper to breathe again but may worsen the central BUT, if I as the machine, can cycle between two pressure and with a good gap between them & do this at the sleepers normal or minimum breath rate, I stand an excellent chance of getting the sleeper breathing normally again. Timed bilevels do this. That is how they resolve centrals. The interesting aspect of this is that a bilevel DOES USE PRESSURE to get the central resolved, but not by applying it in a steadily increasing fashion (which is how Autos adjust). The bilevel cycles between exhale & inhale settings.

DSM


* Re vendors reduced flow for scoring, am going from memory & the actual numbers may be just a little different

[dsm]

This is all very interesting. I'm learning some limitations on my new ResMed S8 Autoset II. I'm not getting my AHI's below 5 often enough. Correct me if I'm wrong, but whether obstructive or central apneas, isn't oxygen saturation what we are really interested in? If so, why isn't more emphasis placed on recording that during the course of PAP treatment?

If you AHI score when broken down into AI & HI shows little to no AI then you are doing very well.

Resmed's score HI differently from Respironics - just because the reported score looks different doesn't mean exactly the same respiratory events are not occurring.

The trap here is not to buy the machine that tells you the nicest 'story' when the underlying respiration is identical. That is another area of confusion that occurs in regard to 'must have the lowest AHI'. The AHI score is not really an accurate arbiter of what is happening. But, as poor as it is, it is better than nothing and it provides relativity from night to night as to how good bad your therapy direction is heading. Comparing one brands score against another tends to be very 'iffey'



DSM

[track]

Resmed's score HI differently from Respironics - just because the reported score looks different doesn't mean exactly the same respiratory events are not occurring.

I can only speak from my own experience with the two machines but for ME....I typically have less than .5 HI on my remstar. On the resmed my HI was typically around 4. On the other hand my AI on the resmed was typically about 1.0 whereas on the remstar it is around 2.0. My overall AHI is running less than half what it ran on the resmed and I have actually got below one whereas with the resmed I never got below 3....but most importantly I feel more rested on the remstar.

[dsm]

Resmed's score HI differently from Respironics - just because the reported score looks different doesn't mean exactly the same respiratory events are not occurring.

I can only speak from my own experience with the two machines but for ME....I typically have less than .5 HI on my remstar. On the resmed my HI was typically around 4. On the other hand my AI on the resmed was typically about 1.0 whereas on the remstar it is around 2.0. My overall AHI is running less than half what it ran on the resmed and I have actually got below one whereas with the resmed I never got below 3....but most importantly I feel more rested on the remstar.

Absolutely

How you feel over time is the best arbiter for any of us. Low scores are a helpful guide but don't always go hand in hand with best results we feel.

DSM

[ozij]

I had a clear memory of "frank apnea" used by Resmed - I no longer find it there. It is however prevalent in many medical papers.

I think your attempt to describe similarities between machines, when these do not exits, creates additional confusion.
Confusion is cleared by using the terms the vendors use, and explaining them, not by using new ones.

All the machines have to guess indirectly what distinguishes a central apnea from an obstructive one. Each uses an operational definition - and you seem to be adding one of your own.

An apnea is cessation of air flow.
Nobody waits for a 100% cessation in order to say "that was an apnea, I better do something".

The only machine that attempts to distinguish a central apnea from an obstructive apnea, based on amount of flow is the Devilbiss. They say: if its more than 95% reduction, we won't respond because we know that 85% or the time, those are central apneas, we'd rather err on the side of caution for the other 15%.


Velbor was thorough enough to create and publish this comparison chart, based on the texts published by the vendors.
[/quote]

These are operational definitions used by automatic machines for identifying any apneas. Having discovered an apnea, the machine now has to figure out if that apnea is cause for raising pressure or not.

Respironics, figures out an apnea is central if it has seen a lack of response to rising pressure wihtin 3 minutes.
ResMed figures out an apnes is central if it occurs above 10 cms of pressure - and will not respond to any apnea that appears above that pressure.
Sandman (Puritan Bennett) figures an apnea is central if it hears the heartbeat.

None of the above educated guessing techniques is 100% right.
Because of the above rules, you will find Sandman for instance mistreating a whole bunch of people whose central apnea are not accompanied by the sound of their heartbeat (there is large presonal variation in that).
You will find ResMed ignoring and reporting many obstructive apneas for people who have obstructive apneas unaccompnied by snores and flow limitation above 10c cms for some people.
You will find the pressure being driven much too high by Respironics for some people.
There is no best machine for everyone.

The medical definition of a central apnea has to with its cause: It is breathing cessation as a result a lack of any attempt to breathe. That lack of effort is measured by the sensors on a person's chest and abdomen in a PSG.

It seem to me , dsm, that when explaining, you don't always distiguish between your thinking of what may be happening or even of what you believe should be happening, and what the vendors state clearly. Your "no flow apnea" distinction is a case in point. You have created a plausile scenario -- but it is not what happens in reality. Your basic assumption is wrong. I would rather attempt to help people understand formally published criteria.

O.

[dsm]

<snip>

It seem to me , dsm, that when explaining, you don't always distiguish between your thinking of what may be happening or even of what you believe should be happening, and what the vendors state clearly. Your "no flow apnea" distinction is a case in point. You have created a plausile scenario -- but it is not what happens in reality. Your basic assumption is wrong. I would rather attempt to help people understand formally published criteria.

O.

Ozij,

I do my best to use clarity when describing what I mean (e.g. No-flow apnea) as you agree 'Frank Apnea' means nothing other than to the person who wrote it.

As for me trying to distinguish my meanings - I have concluded it is near impossible because none of us can agree on definitions no matter what labels we use. The bulk of your post is absolute confirmation of the points I was making - no vendor agrees on what apnea means when they come to scoring it & guess what the average person looks to when reading their reports from their machines.

So yes I plead guilty to not always making my points clear - in a sea of mud but I do try - words just don't always work.

Ozij, I have a very high regard for the points you make here at cpaptalk and for your comprehension of xPAP - you rank very highly (with SWS) IMHO so please don't see my points as aimed at you but at the confusion that gets sown even by well meaning folk among us. I do see misconceptions in some points you make & am sure you see similar in mine. But between us we do pretty well at getting general points across.

Cheers & thanks

DSM

[dsm]

Ozij,

One favour I would ask is can you comment on this point that I made as it is a 'hot button' for me & one I believe is repeatedly a cause of confusion. Please analyze what I am saying & give a perspective on the pertinent point made.

>>>
Do you agree that most newcomers to this discussion group have to go through a lot of confusion before they eventually begin to grasp the mess of definitions apnea appears to cover ? - I am in no doubt !.

So when anyone of us adds repeatedly to that confusion we are not helping. Because, that is exactly how I feel about the confusing statement "A10 does not respond to Apneas over 10 CMs". Again & again we see people misinterpret that to mean that Resmed A10 does nothing about OSA over 10 CMs and that is because the statement is out of context and that most newcomers do not yet know the variety of different event types that in their minds are all just 'apneas' .
<<<


Thanks

Doug

[ozij]

Ozij,

One favour I would ask is can you comment on this point that I made as it is a 'hot button' for me & one I believe is repeatedly a cause of confusion. Please analyze what I am saying & give a perspective on the pertinent point made.

>>>
Do you agree that most newcomers to this discussion group have to go through a lot of confusion before they eventually begin to grasp the mess of definitions apnea appears to cover ? - I am in no doubt !.

An apnea is cessation of breathing - that is not difficult to grasp.
A hypopnea is breathing which is too shallow, also not difficult to grasp.
A flow limitation - breathing which stumbles like a stream flowing over stones.

That is all a newcomer has to grasp in order to undrestand the fuctioning of an APAP. The operational definitions collected by Velbor become important only when people want to understand how the machines decide what is what.

So when anyone of us adds repeatedly to that confusion we are not helping. Because, that is exactly how I feel about the confusing statement "A10 does not respond to Apneas over 10 CMs".

You feel the statement is confusing.
I feel that there is nothing inherently confusing about the statement.

Again & again we see people misinterpret that to mean that Resmed A10 does nothing about OSA over 10 CMs and that is because the statement is out of context and that most newcomers do not yet know the variety of different event types that in their minds are all just 'apneas' .

Which is why clarifyign the distiction between the types of events helps.
If a person does not have the right background knowledge (context) for understanding any statement about any APAP's ResMed's respnse rules, I do my best to give the right context.
The right context is maintaining consistently that there are different types of breathing events, and most APAPs are programmed to have a different response to eacht type of event.
I do not agree that a statement describing ReMed's response rules to apneas adds to confusion about the distinction between apnea, hypopnea, and flow limitation.
I do not agree users have trouble understanding the ResMed will respond to flow limitations at any pressure, will respond to snores at any pressure, will not respond to hypopneas at all and will only respond to apneas when the pressure is less than 10 cms.

The doctors who planned the ResMed algorithm based it on non-technical definitions of breathing events, and not on the opertaional ones. It has been stated - again and again that that policy has served ResMed very well in treating the majority of people who suffer from obsturctive sleep apnea.
The technicians had to figure out how the machine will identify each event in the data it gathers - hence the complicated operational definitions - and the different measurements achieved by the machines.

I do think your hot button response adds to the confusion when you start speaking of "OSA patterns" instead of pointing out specifically that the ReMed will respond to snores at any pressure, will respond to flow limitations at any pressure, and those are very good pecursors of obstruction the help the ResMed pre-empt many apneas. The Resmed will not respond to apneas above 10 cms. An apnea is not the disease call "Obstrutive Sleep Apnea Hyponea Syndrome" or OSA for short..

There are different kinds of events. Like other APAPs, the ResMed has a different, distinct response to each type of event.


O.

[DoriC]

Ozij,dsm, you are both so knowledgeable and have helped more people than you'll ever know. This thread makes my brain hurt! Just wanted to give a newcomer's perspective. I started reading this forum 2weeks before my husband was given his RX. He was titrated at 13cms. Very few things made any sense to me at the time but something did jump out at me that I thought I understood perfectly. "Resmeds do not respond to apneas over 10cms". So I thought I was really a hotshot when I told our Internist we wanted only the Respironics Auto, no Resmed for us. It lessened my confusion of choice at the time. I think we have a good machine, thanks to this forum, and my hubby is doing well, but it's only now after 8months that I finally think I understand the A10 algorithim and I read here almost daily and have learned so much. I also just found out that the Resmed was used for his sleep study and he had the best night's sleep of his life. So now there's that little man on my shoulder wondering what results we would have gotten with a Resmed. Again,for all of us, thank you.

[Wulfman]

Ozij,dsm, you are both so knowledgeable and have helped more people than you'll ever know. This thread makes my brain hurt! Just wanted to give a newcomer's perspective. I started reading this forum 2weeks before my husband was given his RX. He was titrated at 13cms. Very few things made any sense to me at the time but something did jump out at me that I thought I understood perfectly. "Resmeds do not respond to apneas over 10cms". So I thought I was really a hotshot when I told our Internist we wanted only the Respironics Auto, no Resmed for us. It lessened my confusion of choice at the time. I think we have a good machine, thanks to this forum, and my hubby is doing well, but it's only now after 8months that I finally think I understand the A10 algorithim and I read here almost daily and have learned so much. I also just found out that the Resmed was used for his sleep study and he had the best night's sleep of his life. So now there's that little man on my shoulder wondering what results we would have gotten with a Resmed. Again,for all of us, thank you.

Kick his butt off your shoulder......your hubby is gonna get jealous!

Trust me......he has the "right" machine.

Den

[dsm]

The absolutely true statement anyone can make about any brand's algorithm is ...
Does the machine's algorithm adequately sense patterns of OSA events and pre-empt them to the point that the user is getting good therapy. !.

And Ozij, I think we will just have to agree to disagree completely over the usefulness of quoting that hackneyed, out of context A10 statement. DoriC understands the point I made, I am really quite surprised that you don't or won't.

Cheers

DSM

[dsm]

Ozij,dsm, you are both so knowledgeable and have helped more people than you'll ever know. This thread makes my brain hurt! Just wanted to give a newcomer's perspective. I started reading this forum 2weeks before my husband was given his RX. He was titrated at 13cms. Very few things made any sense to me at the time but something did jump out at me that I thought I understood perfectly. "Resmeds do not respond to apneas over 10cms". So I thought I was really a hotshot when I told our Internist we wanted only the Respironics Auto, no Resmed for us. It lessened my confusion of choice at the time. I think we have a good machine, thanks to this forum, and my hubby is doing well, but it's only now after 8months that I finally think I understand the A10 algorithim and I read here almost daily and have learned so much. I also just found out that the Resmed was used for his sleep study and he had the best night's sleep of his life. So now there's that little man on my shoulder wondering what results we would have gotten with a Resmed. Again,for all of us, thank you.

Kick his butt off your shoulder......your hubby is gonna get jealous!

Trust me......he has the "right" machine.

Den

Den

If a majority of people say that when using a Resmed that their AI scores tend to be quite a bit lower than when using a Respironics - who is getting the better therapy ?. To be fair, there are many other considerations but the reason I ask is because that is what people generally report. Very low AI score but very high HI score & I think we can agree that as has been said many times comparing AI & HI between brands is very doubtful.

As posted above, the true measure of how good an Auto is, is if it can pre-empt the OSA events that someone is prone to and can do so to the point where the user feels their therapy works well.

Both Resmed and Respironics are proven and successful devices.

The one issue that crops up repeatedly that DOES make a difference for some users, is the different speeds that Resmeds respond to events when compared to how Respironics responds - so this issue is to do with how fast Resmeds respond. The A10 algorithm when under 10 CMs, the further it is below 10 CMs the quicker it will raise pressure when sensing signatures of looming events or when hypopneas / apneas have been scored. The Respironics (as best as I recall from the patent data) works at the same speed of response no matter what the pressure setting & many people have commented that they find the Respironics Autos 'softer'. Some have used the word aggressive to describe the Resmed response. These are people who tend to be in the lower CMs settings (around 6-10).

Cheers

DSM

[Plowboy]

I am so intimidated at this point I think I would rather go back and take calculus again. I am very new here and am still trying to figure out my data. Seems to me from what everyone has talked about in this thread that a person should just try and find their "Ideal Pressure" and say to hell with all this autoadjusting stuff. I am going to try and set mine to a set pressure and see if that makes a differance, and I agree with a previous post, they should set up newbies on CPAP only until an ideal pressure is found.

Phil