Just feel like whining....

[ozij]

If you had no central apneas during your sleep test where they can definitively discern the ones that matter, I would not assume that the apneas labeled as centrals by your home machine are actually significant central apneas. They may be harmless pauses in breathing or they may be obstructive and mislabeled central by your home machine. There is no way to know.

No documented drop below 90% should be ignored as completely insignificant, I don't think, from what little I know. And I don't doubt the reality of the apnea, either. I am only saying that (1) occasional pauses in breathing can occur at changes of sleep stages, and those "centrals" may not be scored as significant during a sleep study, as I understand it, from what I've read by the experts here and elsewhere. I am also saying that (2) the apnea that gets labeled a "central" by a home machine may, in fact, be an obstructive event in some cases. I say that because I, personally, doubt how well the home machines do at discerning the difference between obstructive and central.

Machine makers compare their machines' diagnosis of central apnea with a PSG diagnosis. It's not pure guesswork. What kind of error occurs: obstructive misidentified as central, or central misidentified as obstructive are very much machine dependent and patient dependent. For some people, the machines are right 100% of the time.

While some central apneas may indeed be harmless pauses pauses in breathing, other central apneas may be as harmful as obstructive apneas to both your sleep and to your saturation. Since whatever happens in the sleep lab is no more than one night's snap shot, things may be different at home in many ways. Including the appearance of sleep related central apneas that were not observed (or not properly scored) in the lab.

[jdm2857]

OAs are a bit different because you aren't trying to breathe, but chances are if they are sparstly sprinkled (and short lived) amongst CAs and Hypops, then it could be a stray electron or someting that made the PAP mark them down.

Methinks you reversed OAs and CAs.

[jamieay]

Echo - I'm at 10/6.

Jamie

[jamieay]

OK - PLEASE HELP ME UNDERSTAND THIS!!!

I've just woken (waken? wakened?) from my best night in 6 weeks! My AHI was 4.0 - my best yet! All I did differently was to actually loosen my mask (actually, loosened it all the way and readjusted it from scratch per the manufacturer's instructions). According to the card data, my leakage rate is 2% (well, it show 27%, and the mask leaks 25% per manufacturer's data, so it's 2% above the minimum). Can over-tightening my mask cause CAs or cause the machine to think I'm having CAs?

I feel great but wish to hell I understood what works and what doesn't!

Jamie

[jnk]

Thanks for your comments, ozij. VERY helpful and educational, as always. These are my uneducated reactions, straight from the heart, meant to learn more from you:

Machine makers compare their machines' diagnosis of central apnea with a PSG diagnosis.

And I compare my dashing good looks to a young Robert Redford, but that doesn't make it so. Right?

What kind of error occurs: obstructive misidentified as central, or central misidentified as obstructive.

I agree.

For some people, the machines are right 100% of the time.

How many is "some"? For what percentage of people is the machine wrong and by what percentage? I think I missed that study, if there was one done with all the different masks, for example, that patients use in the real world. Are there any doctors who would take the word of a home machine over a PSG in diagnosing a form of central sleep apnea?

sleep related central apneas that were not observed (or not properly scored) in the lab.

Is your position that home machines are superior to or as good as PSGs when it comes to accuracy in differentiating centrals from obstructives?

[carbonman]

For some people, the machines are right 100% of the time.

Half of the machines can be part right all of the time,
some of the machines can be all right part of the time,
....but, all the machines can't be all right all of the time.

--I said that.

[-SWS]

I am also saying that (2) the apnea that gets labeled a "central" by a home machine may, in fact, be an obstructive event in some cases.

Is your position that home machines are superior to or as good as PSGs when it comes to accuracy in differentiating centrals from obstructives?

Regarding central apnea detection, the home machines fare MUCH better with specificity than sensitivity. That means they are frequently going to misidentify central apneas---and erroneously flag them as obstructive instead; but that when they detect central apneas, those are usually central apneas.

Thus if anyone prolifically scores central apneas on their home machine that somehow didn't manage to present during a one-night snap-shot PSG, then that person has a central apnea issue requiring follow-up by the doctor. Some people are variable regarding how they present their central apneas from night to night: they can present none or few on one night while presenting central apneas more prolifically on other nights.

I agree that it's not uncommon to have a few central apneas. A few here and a few there are not even worrisome. Mine tend to cluster during wake/sleep transitions.

[jnk]

when they detect central apneas, those are usually central apneas.

Interesting. And I believe you. But are there any numbers available on that, collected from real world conditions, and/or comparisons on which FOT machines do better or worse with that?

[jnk]

OK - PLEASE HELP ME UNDERSTAND THIS!!!

I've just woken (waken? wakened?) from my best night in 6 weeks! My AHI was 4.0 - my best yet! All I did differently was to actually loosen my mask (actually, loosened it all the way and readjusted it from scratch per the manufacturer's instructions). According to the card data, my leakage rate is 2% (well, it show 27%, and the mask leaks 25% per manufacturer's data, so it's 2% above the minimum). Can over-tightening my mask cause CAs or cause the machine to think I'm having CAs?

I feel great but wish to hell I understood what works and what doesn't!

Jamie

I don't think those are percentages your machine is reporting. I think it is actual leak. I don't own that machine though.

I wish I understood more, too, jamieay. For example, the valuable posts made here by ozij and -SWS are making the point, as I understand them, that if your machine is calling those apneas "centrals," than they are very likely centrals, and you would want to mention that to your medical team, just in case they may be significant in relation to some other condition.

As -SWS points out, a few centrals are generally no big deal. A lot of centrals, even if they come and go night to night, may very well be worth looking into. So my efforts to be calming in my earlier post may have gone too far, in that it might make you ignore something that could be significant in the sense of there being a need to keep an eye on it, depending on what your docs say. (Is that closer, O&S?)

It is great you are finding something that is helping how your therapy is going. What a good proof of the value of patients' seeing their data! (That gives you something to judge your mask-adjustment experiments by, for example.) And I hope it continues to go well and that you keep learning, just as we all are here.

[jamieay]

I don't think those are percentages your machine is reporting. I think it is actual leak. I don't own that machine though.

On the PR System One REMStar with Bi-Flex my understanding (and please someone - correct me if I'm wrong here!) is that the leak rate is the GROSS leak rate - it doesn't account for the type of mask you use. On other machines you can enter the mask type so that the machine subtracts off the normal leakage that the mask is designed for (the vent holes and all that) so all it reports is the net leakage due to adjustment issues, etc.

Is that correct? I'm still very new to this.

Jamie

[ozij]

OK - PLEASE HELP ME UNDERSTAND THIS!!!

I've just woken (waken? wakened?) from my best night in 6 weeks! My AHI was 4.0 - my best yet! All I did differently was to actually loosen my mask (actually, loosened it all the way and readjusted it from scratch per the manufacturer's instructions). According to the card data, my leakage rate is 2% (well, it show 27%, and the mask leaks 25% per manufacturer's data, so it's 2% above the minimum). Can over-tightening my mask cause CAs or cause the machine to think I'm having CAs?

I feel great but wish to hell I understood what works and what doesn't!

Jamie

Overtightening your mask can cause pain.
Pain can cause tossing an turning, arousals and sighs. During those times, you may stop breathing, even though your airway is unobtructed -- and the machine will record a breathing stop that is not obstructive, i.e. a central apnea.

O.

[M.D.Hosehead]

jamieay, you are correct that the leak shown on the report is the total of the mask's ventilation (they all vent some air) plus whatever is leaking from around the seal on your face.

So you have to look up the vent rate for your mask, which you will find in the literature that came with the mask. There will be some kind of chart that shows the normal vent rate at each pressure; because as your machine's pressure increases, the holes in the mask vent more liters per minute. When you subtract the mask's vent rate from the total leak rate, the remainder is the amount of air leaking from where the mask seals to your skin. Ideally that would be zero.

The problem is that with BIPAP, the pressure doesn't remain constant. Bi-flex and auto introduce even more pressure variation. You simply pick a number from the chart in the mask's literature that seems to approximate your average pressure, and use that figure to subtract from the total leak rate that's reported. Obviously the result can't be more than a ballpark estimate. I have tried getting a leak reading after turning off both the flex and the auto, but it doesn't seem to be that much more accurate.

[ozij]

Thanks for your comments, ozij. VERY helpful and educational, as always. These are my uneducated reactions, straight from the heart, meant to learn more from you:

Machine makers compare their machines' diagnosis of central apnea with a PSG diagnosis.

And I compare my dashing good looks to a young Robert Redford, but that doesn't make it so. Right?

I have no idea how you look. However, you can bet that if you put on a wig in a Robert Redford look alike competition, the other competitors would snatch it off your head in a second. And they would love doing it - it would make the competition so much easier for them. All APAP companies have great stakes in looking good -- they are not going to fake things that can be checked and disproved by their competitors.

What kind of error occurs: obstructive misidentified as central, or central misidentified as obstructive.

I agree.

For some people, the machines are right 100% of the time.

How many is "some"? For what percentage of people is the machine wrong and by what percentage? I think I missed that study, if there was one done with all the different masks, for example, that patients use in the real world. Are there any doctors who would take the word of a home machine over a PSG in diagnosing a form of central sleep apnea?

If I know a machine uses a technique that can identify central apneas perfectly in some people, and I had a machine identifying central apnea in my breathing, then I would take notice of that -- since, as -SWS said - there is very little misidentification there. Machines (and internet forums) should never be used for diagnosis. That does not mean their data is to be discarded or ignored. My blood tests don't give me a diagnosis -- they give me and my doctor valid information to go on.

If you had no central apneas during your sleep test where they can definitively discern the ones that matter, I would not assume that the apneas labeled as centrals by your home machine are actually significant central apneas. They may be harmless pauses in breathing or they may be obstructive and mislabeled central by your home machine. There is no way to know.

So my efforts to be calming in my earlier post may have gone too far,

I agree. I would say that statement came from your kind heart, but is rather shaky as far as facts are concerned.

in that it might make you ignore something that could be significant in the sense of there being a need to keep an eye on it, depending on what your docs say. (Is that closer, O&S?)

Yes, that is closer.

sleep related central apneas that were not observed (or not properly scored) in the lab.

Is your position that home machines are superior to or as good as PSGs when it comes to accuracy in differentiating centrals from obstructives?

Do you happen to have studies showing perfect inter-scorer reliability in PSG? Do you happen to have studies showing that no matter what the lab, and no matter what the technicians' accreditation, scoring remains reliable and valid? Ditto for studies showing there is no night to night variablility in PSG results - is you trust of one night's PSG results based on any of those? It is my position the humans make mistakes, some are incompetent and a PSG is a snapshot of one night. It is also my position that - within know limitations - the machines report reliable data, that is quite valid as well. Therefore, I would not pooh pooh discrepant results from a machine at home by saying "nah, that's just a stupid machine, the PSG must have been right". I would take the discrepant result seriously, and have them investigated by a competent doctor. A diagnosis of a condition, and a prescription for therapy both entail far more than the counting and characterization of apneas, these functions should not be confused.

I would be very interested in discussing the studies on which you base your statements.

[LoQ]

Thanks for the insight jnk! I do wonder if those centrals are really centrals or are obstructive. Here's another data point - From my first sleep study -

"The patient had no obstructive apneas and 92 hypopneas, resulting in AHI of 19.6 / hr."

then later

"Impression - Moderate obstructive Sleep Apnea worse during REM sleep and in supine position"

How can I has "no obstructive apneas" AND "moderate obstructive sleep apnea"? Doesn't make sense to me.

Argh. I want a freaking nap.

Jamie

That is confusing, I admit. I think what you have to realize is that "obstructive sleep apnea" is the title of a disease. It is an umbrella term for lots of different variations. It's the diagnostic term, regardless of what your variation is. For that reason, I sometimes use sleep-disordered breathing, which I think isn't as confusing to people who do not have apneas. It may be that the term sleep-disordered breathing also covers other things besides OSA, but in any event, it's just a diagnostic term, not a description.