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General Discussion on any topic relating to CPAP and/or Sleep Apnea.
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barry15
 
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Clear Airway Apnea = Central Apnea?

Postby barry15 on Thu Dec 31, 2009 1:15 pm

I recently got a Respironics System One Auto machine, and I notice that in the daily report, AHI is composed of three things – Obstructive Airway Apneas (OA), Hyponeas (H), and Clear Airway Apneas (CA).

My first question is this – is Clear Airway Apnea just another term for Central Apnea? I don’t see anyone except Respironics using the Clear Airway Apnea terminology, even with a Google search. I like the fact that this machine claims to be able to distinguish CA’s from OA’s, which is something that my old Resmed Autoset II didn’t do. They say that they don’t make any change to the pressure due to CA’s, but they do report them and they are included in the AHI.

I have been varying various factors, including the “flex” settings (A-Flex, C-Flex, and no Flex) and the pressure limits (slightly). I have also been trying both my Ultra Mirage nasal mask and my Ultra Mirage II full face mask. The preliminary data seems to show that my OA index is more or less the same under any scenario (about 0.5 on average), my H index is about the same also (about 1.7 on average), but my CA index is higher with the full face mask (about 2.3 rather than about 0.5 for the nasal mask.

My second question is this – is this significant? Does it matter? To look at it more broadly, my AHI is about 2.5 with the nasal mask and about 5 with the full face mask. I plan to continue to collect data, to separate all the various variables, but can anyone give me any insight about this seeming difference between the full face mask and the nasal mask? Is there some reason that the full face mask should cause more CA’s, or is it likely just the effect of how the machine distinguishes a CA (by sending out several puffs of air when it detects an apnea)? Even if it is the latter, the AHI is still almost twice as high with the full face mask, so it makes me wonder. I have nasal issues, and the full face mask is more comfortable for me, but I don’t want to compromise my therapy if it matters.

This might sound like a very picky, technical question, but I have noticed that there are some very knowledgeable people here, and I thought I would see if I could gain some insight.

Before anyone asks, I don’t have the Encore Pro 2 software yet, but my sleep doctor’s office is very cooperative and less than five minutes away. They will gladly print me out my data every week at no charge, so I have been getting the information that way.

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Re: Clear Airway Apnea = Central Apnea?

Postby BleepingBeauty on Thu Dec 31, 2009 1:59 pm

Hi, barry, and welcome aboard. :)

barry15 wrote:I recently got a Respironics System One Auto machine, and I notice that in the daily report, AHI is composed of three things – Obstructive Airway Apneas (OA), Hyponeas (H), and Clear Airway Apneas (CA).

My first question is this – is Clear Airway Apnea just another term for Central Apnea? I don’t see anyone except Respironics using the Clear Airway Apnea terminology, even with a Google search. I like the fact that this machine claims to be able to distinguish CA’s from OA’s, which is something that my old Resmed Autoset II didn’t do. They say that they don’t make any change to the pressure due to CA’s, but they do report them and they are included in the AHI.


I believe so, yes. My understanding is that the new PR One does report central apneas. Do you know if your sleep study indicated that you experienced centrals? Some people with Complex Sleep Apnea need a far more sophisticated machine (adaptive servo ventilation, or ASV) to treat centrals.

I have been varying various factors, including the “flex” settings (A-Flex, C-Flex, and no Flex) and the pressure limits (slightly).


You should only change one thing at a time, and give that change at least a few nights before you change anything else. (If you change two things at the same time, you won't be able to determine what helped and what didn't.)

I have also been trying both my Ultra Mirage nasal mask and my Ultra Mirage II full face mask. The preliminary data seems to show that my OA index is more or less the same under any scenario (about 0.5 on average), my H index is about the same also (about 1.7 on average), but my CA index is higher with the full face mask (about 2.3 rather than about 0.5 for the nasal mask.


Sorry, but I have no idea why a different mask would cause your centrals to either increase or decrease. Could simply be night-to-night variation in quality of sleep, which we all experience, in which case more data collection is needed to make any reliable observation. Hopefully, someone more knowledgeable than me will address this question.

My second question is this – is this significant? Does it matter? To look at it more broadly, my AHI is about 2.5 with the nasal mask and about 5 with the full face mask. I plan to continue to collect data, to separate all the various variables, but can anyone give me any insight about this seeming difference between the full face mask and the nasal mask? Is there some reason that the full face mask should cause more CA’s, or is it likely just the effect of how the machine distinguishes a CA (by sending out several puffs of air when it detects an apnea)? Even if it is the latter, the AHI is still almost twice as high with the full face mask, so it makes me wonder. I have nasal issues, and the full face mask is more comfortable for me, but I don’t want to compromise my therapy if it matters.


As long as your AHI is under 5, you're considered to be effectively treated; what really matters is how you feel. As to the FFM causing more CA's, that's a mystery to me. I would think a FFM might produce a higher AHI if the design of the mask is pushing your lower jaw further back, so as to obstruct your airway. But CA's aren't obstructive, so I'm stymied.

How's your leak rate with each mask? If your leak is under control, you can trust the other data; if you're experiencing too much leak, the data is suspect, because your machine isn't able to give you effective therapy if the air is escaping your mask.

This might sound like a very picky, technical question, but I have noticed that there are some very knowledgeable people here, and I thought I would see if I could gain some insight.


Have no fear in asking questions here. We're a helpful and understanding group. :)

Before anyone asks, I don’t have the Encore Pro 2 software yet, but my sleep doctor’s office is very cooperative and less than five minutes away. They will gladly print me out my data every week at no charge, so I have been getting the information that way.


That's great. :D EncorePro 2 isn't yet available to any patients; there's talk of end-user software for the PR One machines becoming available sometime in 2010, but that's just hearsay.
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Re: Clear Airway Apnea = Central Apnea?

Postby rested gal on Thu Dec 31, 2009 2:21 pm

I think Respironics is calling it "clear airway apnea" because the machine is making an educated guess about what kind of apnea it may be. Without the chest and abdomen "effort" belts that are used in a PSG sleep study, the machine has no way of knowing if the the sleeper is unsuccessfully trying to breathe or not.

Cessation of airflow with no blocked airway and no effort to breathe are the hallmarks of a central apnea...in a live person, anyway!

As I understand it, the PR System One machine tries to determine if the airway is closed or open, by analyzing little pulsing pressures it sends during cessation of airflow from the person. I don't know how consistently or accurately it can distinguish which type of apnea it is... but as far as I know, sans "effort belts", it cannot absolutely, truly measure know whether the sleeper is making an "effort" to breathe.

Since the machine can't absolutely say, "it's a central, without knowing if there was no effort to breathe on the part of the sleeper, I'd say that's why Respironics chose to use another term...clear airway apnea...for what probably was a central. They are carefully (and wisely, imho) not flat out characterizing such an event as a central. They're strongly implying it is, though. :D
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Re: Clear Airway Apnea = Central Apnea?

Postby Doze on Thu Dec 31, 2009 2:23 pm

I recently became interested in that same question, and after a small amount of digging, concluded the same thing: that Clear Airway == Central Apnea.

I've only just become interested in this and could easily be wrong so don't count my vote for too much, but I found some forum posts indicating that Central Apneas are named as such because they are thought to be related to Central Nervous System issues, rather than Airway issues.

The SystemOne definition for Clear Airway is paraphrased (source undisclosed) as:
During an apnea, test pulse(s) are sent and the patient response determines if the apnea occurred while patient has a clear or obstructed airway. If a test pulse creates significant (detectable) flow, the airway is considered to have been clear and it marks the event as Clear Airway (CA). If the test pulse does not create detectable flow, the airway is considered to have been obstructed and an OA is recorded.

So it appears that rather than actually define and report "Central Apneas" which a flow-based device maybe can't be expected to do with certainty (guessing here?), that System One attempts to indicate events it could only explain otherwise as Central Apneas by using the term Clear Airway Apnea, which seems reasonable enough and has the handy side-effect of condensing to the same two-letter acronym "CA" as Central Apnea. Cute. And apparently PR is so confident in the association that they directly include it in their AHI calculation. For all days I've looked at, CA + OA + H = AHI



As a side note, looking at my waveform data from last night, I see a small handful of CA reported, and in each case there is a Pressure Pulse that did not result in a restoration of normal flow. Scattered elsewhere, I see a few other Pressure Pulses that did seem to restore flow, and in one of those cases, a Hypopnea was marked shortly thereafter. This fits exactly with the definition I've paraphrased above. I had no OAs last night; yay for me!

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Re: Clear Airway Apnea = Central Apnea?

Postby GumbyCT on Thu Dec 31, 2009 2:52 pm

Welcome Barry, it is nice you can get printouts from your doc. It is difficult being the 1st one on the block to have a new machine with new terms even you doc doesn't have any experience with. I think for that reason I would have stayed with the Autoset II.

As already pointed out your leak info would be helpful but that means nothing without knowing the pressure. So in short AHI, pressure, and leak data are most meaningful together and with mask make/model.

If possible posting a daily chart showing your CAA's would go a long way to getting the most help for you.

I am also wondering if you have any trouble exhaling or any other medical issues which could play a role? GERD, asthma?? What position are you normally sleeping in?
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Re: Clear Airway Apnea = Central Apnea?

Postby barry15 on Thu Dec 31, 2009 3:16 pm

Wow, great info, people. Thanks very much. This forum is amazing.

Beauty,

I have been using CPAP for 12 years and haven't had a sleep test for about 8 years. I plan to get one in the spring, but I have been losing significant weight, and the doctor and I thought it would be better to wait until my weight stabilizes to have a new one. My Autoset machine was 8 years old, and I wanted to try the updated technology, and the doctor recommended this System One machine, so I got one.

I understand about changing only one variable at a time, and I know I need much more data before drawing conclusions, but I have two weeks of data with the nasal mask and a week with the full face mask, and this difference just jumped out at me, so I thought I would ask the question.

My leak rate has been very consistently about 30, with a range from about 28 to about 37. As I understand it, that is fine. If not, please let me know.

rested gal,

Thanks for the detailed explanation. I hadn't thought of some of those things, but it makes perfect sense to me. I am going to assume that my Clear Airway Apneas are indeed Central Apneas.

Doze,

I'm looking forward to getting the software to actually look at the waveform data for each day. At this point, the printed data that I get from my doctor's office doesn't contain that information.

Gumby,

I am not aware of any issues that would explain the Clear Airway Apneas, and I don't know if the numbers are significant or not. I sleep on one side or the other, waking every hour or so to turn over. I'll continue to gather data and see what develops. I'm very happy with the machine so far, especially the small size compared to my 8 year old model of the Autoset.

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Re: Clear Airway Apnea = Central Apnea?

Postby rested gal on Thu Dec 31, 2009 3:32 pm

Before people with PR System One machines start becoming alarmed (OMG, my brain forgot to tell me to breathe!! :shock: ) if a handful of "clear airway apneas" appear on their data, check out some of the discussions at the "Links to Centrals" threads:

Links to Central Apnea discussions
http://www.cpaptalk.com/viewtopic.php?p=22702

Particularly keep in mind (no pun intended) the comments from sleepydave and christinequilts:

http://www.apneasupport.org/viewtopic.php?p=24677

In a reply titled "Nope" sleepydave (RRT, RPSGT and manager of an accredited sleep center) responds to honda's question:

honda wrote:

Thanks for the comments, one other question though, do the 4 central apneas have any significance ?


None whatsoever.
sleepydave


sleepydave's nickname on cpaptalk is "StillAnotherGuest" (SAG)

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http://www.cpaptalk.com/viewtopic.php?p=47781#p47781

christinequilts (who was diagnosed with almost pure Central Sleep Apnea -- severe case) wrote:

6 centrals is not a lot- less then 1 per hour, and is perfectly normal. Everyone has central apneas- take 3 or 4 very slow & deep breaths right now, then count how many seconds after the last inhale until you feel the need to inhale again. Was it more then 10 seconds? If it was, you just had a central apnea. Next time you sigh take note how long before you inhale again....yep, another central apnea. Yawn? same thing can happen. Pick up a heavy box or weight- did you remember to breath? if you didn't, then you had another central apnea. Think of what you hear exercise trainers lecture about breathing while exercising- its human nature to not breath when we exert themselves.

Of course all of these are awake apneas- but any time you don't breath for 10 seconds, you technically have an apnea. While sleeping, you can have similar things happen- you can take several deep breaths and not need to breath for several seconds. During transitions between sleep stages, it is common to have central apneas because the acceptable levels of O2/CO2 are different for each stage...sort of like when you're still going 55MPH as you enter the 35MPH zone. When you turn over at night, it is common to not take a breath- just like when you lift something or exercise when awake. In people with OSA, they don't consider centrals a problem until they are well above 5 per hour- central apneas can be a symptom of OSA, just like snoring, arousals, etc. A few centrals are nothing to worry about- most sleep labs don't get concerned about centrals unless there are a lot of them.

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More wise words from that very intelligent lady -- christinequilts:

Having CENTRAL SLEEP APNEA, as a diagnosis, is rare. Having a few central apneas during the night isn't, its very common & is completely NORMAL.

http://www.cpaptalk.com/viewtopic.php?p=179463#p179463
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Re: Clear Airway Apnea = Central Apnea?

Postby GumbyCT on Thu Dec 31, 2009 3:52 pm

barry15 wrote:My leak rate has been very consistently about 30, with a range from about 28 to about 37. As I understand it, that is fine. If not, please let me know.
Without knowing your pressure those numbers mean nothing. Leak and Pressure should always be used together. Including which mask make/model is even more, even more ;) meaningful.

EDIT: a detailed graph of the pressures and leak are even more, even more meaningful. A graph will show spikes you won't see looking at just numbers, spikes can lead to events when the pressure drops due to leaks. Leaks and pressure should always be used together.
Last edited by GumbyCT on Thu Dec 31, 2009 4:01 pm, edited 1 time in total.
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Re: Clear Airway Apnea = Central Apnea?

Postby rested gal on Thu Dec 31, 2009 3:55 pm

More of christinequilt's well informed comments:

http://www.cpaptalk.com/viewtopic.php?p=15061#p15061
christinequilts wrote:
THink about when you exercise or concentrate hard- if your not aware you can hold your breath which is essentionally central apnea. Turning over in your sleep is basically like an exercise- you go from doing nothing to moving. If you were to have your breathing monitored while you are awake you would see a lot of 'central' events.

----

and here, where Christine was accidentally "guested":
http://www.cpaptalk.com/viewtopic.php?p=6176#p6176

christinequilts wrote:
Most people- even those without sleep disorders- have a few central apneas while sleeping. A common cause is when you roll over...have you ever noticed when you're exercising or lifting something heavy that you hold breath unless you actually think about your breathing? The same thing can happen at night as you toss and turn. THere are other things that cause centrals too- there is a certain amount of variance in our breathing patterns when we sleep just like there is when we're awake.

I wouldn't worry about central events unless there were a significant number per hour
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Re: Clear Airway Apnea = Central Apnea?

Postby FeistyWifey on Thu Dec 31, 2009 4:57 pm

Barry, there is no insignificant question. Ask, ask, ask. (Besides, nobody can ask more teeniney questions than I do, and I can't articulate the way you do). People on this Forum have been wonderful to us. You will be very happy here. Congratulations on the weight loss -- that's tough to do in my experience!

I'm just throwing this question out there to all the guys with beards (and my husband has a beautiful beard so I'd like to know for myself as well): could it be that the beard is affecting the seal of the full face mask when it might not do that with the nasal mask? If so, what methods could be used to deal with any possible leaks -- taping, Pap Cap, any other tips?

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Re: Clear Airway Apnea = Central Apnea?

Postby FeistyWifey on Thu Dec 31, 2009 4:59 pm

P.S. Great beard, Barry! My husband has Centrals, so we'll be pulling for you to get your perfect set-up.

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Re: Clear Airway Apnea = Central Apnea?

Postby barry15 on Thu Dec 31, 2009 5:18 pm

GumbyCT wrote:
barry15 wrote:My leak rate has been very consistently about 30, with a range from about 28 to about 37. As I understand it, that is fine. If not, please let me know.
Without knowing your pressure those numbers mean nothing. Leak and Pressure should always be used together. Including which mask make/model is even more, even more ;) meaningful.

EDIT: a detailed graph of the pressures and leak are even more, even more meaningful. A graph will show spikes you won't see looking at just numbers, spikes can lead to events when the pressure drops due to leaks. Leaks and pressure should always be used together.


Good points, thanks. My pressure has been set in the range from 6.5 to 9, and mostly it is about 7.5 on average. Looking at the graphical representation of leak rate on the Daily Details report, it looks like it gets up to about 50 from time to time, and has averaged about 30 most nights. The daily reports have always indicated 0.0 minutes in Large Leak, for whatever that is worth. My nasal mask is an older Ultra Mirage one, and my full face mask is a new Ultra Mirage II one.

One setting I have not messed with yet is the System One resistance setting (intended for Respironics masks). I have it set at X1, but perhaps it should be off, since neither of my masks is a Respironics one. I will try turning it off eventually, to see if that makes any difference. Does anyone have any insight to offer with respect to this setting on the System One?

I'll look more closely at the daily reports to try to understand the timing of the CA's. I have a feeling that they are mostly happening when I am awake, trying to fall asleep. I haven't kept a detailed enough sleep log to really be able to tell, but when I manage to get hold of the software, I will be able to look more effectively, as I will have a better memory of the night before when I can look at the data each day, rather than once a week. I can see the times I get up to pee (2 or 3 times a night, usually) by the break in the lines, so I can look to see what events happen soon after one of those breaks. My initial impression is that many of my CA's and many of my H's happen at those times, while trying to get back to sleep, which can sometimes be a problem. Often I will be awake for an hour in the middle of the night, and if I am looking at my data the next day, I can look specifically at those times to see if there are any "events" reported.

As rested gal has indicated, my rate of CA's is probably not high enough to be concerned about, but there is a definite difference between the nasal mask and the full face mask (based on my preliminary data), and I thought it would be worth asking about it. I have learned some things from this thread already. It is amazing to me how quickly and how thoroughly people respond on this forum. Thank you all, with a special thanks to rested gal for the links to threads on Central Apneas.

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Re: Clear Airway Apnea = Central Apnea?

Postby barry15 on Thu Dec 31, 2009 5:37 pm

FeistyWifey wrote:Barry, there is no insignificant question. Ask, ask, ask. (Besides, nobody can ask more teeniney questions than I do, and I can't articulate the way you do). People on this Forum have been wonderful to us. You will be very happy here. Congratulations on the weight loss -- that's tough to do in my experience!

I'm just throwing this question out there to all the guys with beards (and my husband has a beautiful beard so I'd like to know for myself as well): could it be that the beard is affecting the seal of the full face mask when it might not do that with the nasal mask? If so, what methods could be used to deal with any possible leaks -- taping, Pap Cap, any other tips?


Thanks for your kind comment on my beard. In that picture it is at one of its "short" points. I only trim it every 5 or 6 weeks, so it gets longer and curlier eventually. I read some of your posts about your husband's Central Apneas with interest, as I didn't know anything about the ventilator machines (and I still haven't researched them). I hope that your husband's upcoming sleep test helps and that he can get a new machine, in the hopes that it will make things better. All of us here know how awful it is not to be able to sleep.

My weight loss has been nothing short of amazing to me. So far I am down almost 70 pounds, in about 8 months, but I have a long way to go, if I can keep it up. It has actually not been difficult, only tedious, as it has required a lot of discipline to control exactly what I eat. If I eat "right", I am actually less hungry than when I was eating almost twice the calories, and it was my insatiable hunger that caused me to gain so much weight.

As for your question, I haven't ever noticed a problem with mask seal because of my beard. Up until now, I have used either a nasal mask or nose pillows, and this new full face mask is the first time I have tried that approach. I like it because I have nose issues (long, long story), and breathing through my mouth when awake in the night gives my nose a chance to settle down a little. I can't tell if I am actually doing any mouth breathing when I am asleep or not. I breathed exclusively through my mouth for most of my life, until I had to learn to breathe through my nose when asleep, so I could use CPAP, and now I think I have forgotten how to breathe through my mouth when I am asleep. I'm not sure I want to relearn to do that, either, as it is a problem with the nasal mask or nose pillows.

I put some additional leak information in a post above, and at this point, I see no difference in the data for the nasal mask or full face mask, so I don't think that leaks are the reason for the increase in CA's, but it is early days yet, and I will keep it in mind.

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Re: Clear Airway Apnea = Central Apnea?

Postby Muse-Inc on Fri Jan 01, 2010 1:54 am

While I had no centrals noted during my PSG, when I got my AutoSet II, my doc and I discussed them when talking about what pressure range to set given ResMed's A10 algorithm. He said centrals are common when falling asleep and often occur when one changes sleep stages.

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Clear Airway Apnea = Central Apnea? NO!!!!

Postby Muffy on Fri Jan 01, 2010 4:30 am

rested gal wrote:In a reply titled "Nope" sleepydave (RRT, RPSGT and manager of an accredited sleep center) responds to honda's question:

Oh, that guy thinks he's so smart.

"IMHO", PR SystemOne will perform no better that the ballistocardiography of PB420E (which, when you think about it, really isn't all that hot):

It's a 50-50 Shot

And I believe that neither ballistocardiography, pressure pulsation nor FOT will accurately identify central apneas because

The pathophysiology of obstructive sleep apnea and central sleep apnea overlap considerably. During normal inspiration, neuronal discharge to the diaphragm and dilator muscles of the pharynx increases. Failure to achieve pharyngeal dilatation in the presence of diaphragmatic contraction results in an obstructive apnea. If the diaphragmatic contractions are diminished, a central sleep apnea occurs. The hypopharynx may or may not be open during a central apnea. Studies have shown considerable narrowing of the hypopharynx during a central apneic event. If the hypopharynx is closed during central apnea and diaphragmatic activity resumes before pharyngeal dilator muscle tone is restored, a mixed apnea results.

Good A Reference As Any

Anyway, they call it a "Clear Airway" event because the airway is "Clear", it probably is, in fact, a central, but chances are there will be tons of 'em that will be missed.

Muffy
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