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Limitations of AHI as a diagnostic tool
#1
Limitations of AHI as a diagnostic tool
This is partially a protest.

Theoretically, I have moderate OSA. My AHI number was 18 during the sleep study, although only 5 of the AHI qualified per Medicare.

Here's my kvetch:

Qualifying for diagnosis, treatment mode, etc. depends on AHI.

Every event (O, C, H) gets one point on the sleep study when AHI is being calculated.

That would be fine and dandy were it not that I have events that string themselves across my screen and disappear. I had 8 events at 40+ (42-48) last night. At that rate, another sufferer could have qualified 3-4 events for one of mine, and scored a whole lot higher AHI as a result.

Then there were many at 30+.

I've had events of 77 seconds, including in the sleep study. My median length was 40, yes, during the sleep study. Yeppers, someone could have 6-7 events, while i'm still working on 1.

This distorts the AHI number. In my case, it is not representative at all of the degree of apnea.

In my sleep study, almost all events were classified as hypopneas (even the 77), except 1 OA (as I recall). Few centrals. Yep!

This is my protest. I'm alot more disordered sleep-wise than my AHI suggests. This is going to make it hideously hard to score a more helpful machine, although I'm working on it.

I have scored a titration study for B-PAP soonish, but I can see I have some major convincing to do or a long time to wait before I get significant improvement in my treatment. I object to this artificial classification of my apneic events per AHI, and it's working against my treatment. Boohoo!  Annoyed-and-disappointed 

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PS My numbers don't need analyzing in this thread. I have another thread for that. I just need knowledgeable empathy.


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Incidentally, has anyone noticed that SleepyHead always classifies super-long events as OSA's? Hypopneas are always 10. CA's are < 40. UA's can be any length 10+. So, there's an event length evidently worked into the algorithm.

I would guess this increases the likelihood that I have absolutely no idea what kind of events I have.
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#2
RE: Limitations of AHI as a diagnostic tool
Did CPAP make your apnea worse, or did your test under-score your severity? If I was in your place, I would get the detailed sleep study charts and see what was going on.

In PSG, AHI should be interpreted as one of many issues, particularly sleep disruption and oxygen desaturation. It is really up to the doctor and technicians to make a case for what their professional judgement indicates is the correct diagnosis and treatment. Too few actually practice this way, but the best ones do.

Sleepyhead does not score or classify the events. It reports the machine's data and event scores.
Sleeprider
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#3
RE: Limitations of AHI as a diagnostic tool
(11-20-2017, 10:11 PM)Sleeprider Wrote: Did CPAP make your apnea worse, or did your test under-score your severity?  If I was in your place, I would get the detailed sleep study charts and see what was going on.  

In PSG, AHI should be interpreted as one of many issues, particularly sleep disruption and oxygen desaturation.  It is really up to the doctor and technicians to make a case for what their professional judgement indicates is the correct diagnosis and treatment.  Too few actually practice this way, but the best ones do.

Sleepyhead does not score or classify the events.  It reports the machine's data and event scores.

My protest is about AHI being a gross underscore in my case (whether sleep study or SleepyHead), which makes it difficult to get the sleep center's attention because they're AHI focused.

It's possible CPAP is making my apnea worse, but I dunno. Dont-know  Maybe "even Steven". I have never had that many ultra-long events in one night on the CPAP as I did last night, but that might be random. It's also only one of two nights I've slept through while on CPAP.

My sleep study did chart desat, and that figured into my CMS AHI. Extra info: My lungs are tested annually for entirely other reasons: I have 100% use of my available lung volume and good desat recovery, so it could be inferred that lung capacity and capability is not a significant factor here. 
Sleep disruption in my sleep study? I had to change beds and rooms, get re-plugged in, and move my stuff in the middle of the night. Oh-jeez Minor disruption noted on the PSG. Right-y-ho.

It's a thought, but a new sleep study—for BPAP titration—is coming soon, so I don't think I'm going to delve into my first sleep study unless I need to get into more elaborate data to present my case to the Sleep Center.

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I wasn't thinking SleepyHead "score[s] or classifi[ies] events, just that I've noticed long events (data in seconds) always end up being OA's. I've thought this was odd, since you could presumably have ultra-long CA's, and it's not always clear looking at the flow rate line what label my events should have.

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PS You can latch this thread onto my data thread if it would be better placed there..
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#4
RE: Limitations of AHI as a diagnostic tool
Well, the problem is that you want Medicare to pay for your machine. The doc can only jump so many hoops. They fudged my stuff just a bit to avoid paperwork. All my events clustered around REM and Near REM, so having a 5 was a fudge as Medicare doesn't count RDI. However, I WOULD have qualified for the low oxygen level alone BUT that required the sleep doc to file an exception. More paperwork they don't want to deal with because well, they don't get paid for all that extra. It's not Medicare's fault. This was the data that the Sleep Doctor Association (whatever they are called) considered diagnosed even though a lot of people who benefit fall outside that zone.

Others have suggested that I would do better with a Bipap. Given that my AHI is under 1 ALWAYS with my current unit, that isn't going to fly with Medicare. So, I'm saving so that I can be ready to score a good deal on a Resmed bilevel in the next year. What I'm working with works for me mostly, but I'm still waking up in the middle of the night. Sadly, this suggestion came right after a good deal on a Resmed bipap disappeared off Craigslist, so the search continues. The reason why I didn't want a Respironics machine is because the apap didn't work for me, I doubt the bipap would work much different.
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#5
RE: Limitations of AHI as a diagnostic tool
as long as it's got a sd card, you could grab a manual and not wait for a Vauto, I would guess they would be at least half the price, probably less. There are enough people here to help you titrate it. I wouldn't worry about brand for a manual either.
mask fit http://www.apneaboard.com/wiki/index.php...ask_Primer
For auto-cpap, from machine data or software. You can set the min pressure 1 or 2cm below 95%. Or clinicians commonly use the maximum or 95% pressure for fixed pressure CPAP, this can also be used for min pressure.
https://aasm.org/resources/practiceparam...rating.pdf
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#6
RE: Limitations of AHI as a diagnostic tool
All I can say is good old NHS (National Health Service) they try their best, however, there is one problem we do have, they will NOT normally treat MILD Sleep Apnea (Apnoea).  This is due to N.I.C.E. (The National Institute for Health and Care Excellence) says it is not worth treating mild sleep apnea due to them saying it can't be treated successfully?
However, some doctors will look at other things in your sleep study and evaluate it on that basis.  Counting the amount of Apneas is not everything, it is the time the apnea lasts and how much the oxygen levels drop, centrals are counted in as well and so is anything else that will affect the patient.  However, there is still doctors here that will just look at the apneas, count them and if you are classed as mild you are out of luck, however, some will refer a patient for a MAD device (suppose that is better than nothing) but usually there is more going on than just Obstructive Apneas, there are centrals and sometimes other things that all make the bigger picture, that is how some of the bigger Sleep Clinics are now beginning to look at things in another light,  They are not just counting the Obstructive Apneas the patient has, but looking at the bigger picture, however, having said that, not all follow this, just the bigger clinics with more knowledgeable doctors that have studied Sleep Apnoea since I was diagnosed.
The was no argument when they looked at my sleep study, he looked at it and showed me, he said every one of these spikes is an apnea (Apnoea = British spelling) and the printout was a mass of black spikes!
He said it was so serious that I needed a machine home now, but if there was any it would be second hand and would have been back from a repair, however, as it happened when he rang through there had been three new machines just delivered.
So I was sent to see the Sleep Nurse and was given a box with a white machine inside, it was an early Sullivan.  Invented by Colin Sullivan PH.D.  Well done that man.  It was a noisy machine (boy was it noisy) but after two nights I felt so much better, in fact I felt I had so much more energy the first night I used it.  I can't remember there being a ramp on the first machines (can anyone remember?) but I was so grateful for it.  The machine was fine, though noisy, but the masks were dreadful with with bit and pads to put on your forehead and air came out everywhere!

I feel sorry for those that are told they are mild and to go loose some weight.  I was anything but big at the time I was diagnosed, okay, I had a few extra pounds, but not that you would notice.  That was one of the comments the doctor said when we had our chat before I got the machine.
It must be soul destroying when you have little energy and told you only have mild sleep apnoea and told you do not qualify for treatment over here, so I suppose, that is in effect what they are trying to say over there as well, unless you fall into a certain category you do not qualify.  It is a bit short sighted though, the patient is only going to get worse and is some bad cases might even die in their sleep.

If I were told that I didn't meet the criteria for a CPAP/APAP machine now I would just go get one by hook or crook and set it up myself.  However, if I needed some of the other more sophisticated expensive machines I don't know what I would do.  They are so expensive and complicated and it does not end there, there is the breakdown to deal with and the cost of that.  I have had eight machines to date, they couldn't keep up with me and packed in Big Grin I would not be able to keep paying out for new machines and masks (I had a big cupboard full) I would maybe be dead now due to a heart attack or something.

So, Halfasleep, you keep pushing for what you need and make a noise.  Go see someone in power or write to them, there is always a politician wanting to flex their muscles and say "Look what I can do".  We used our politicians to push against Government policy when they said they were going to cut funding for Sleep Apnea and everyone would have to pay for their own equipment.  I got a letter from the House of Commons (The Government) saying it was not true, but we all know it was, but it woke the Government up to just how many people out there was prepared to stand up and fight.
If was so effective that people in England got their machines for free (they had to pay for the machine before that, though they got everything else) and clinics started appearing in most hospitals of any size.

So Halfasleep, go stir it up until someone listens.  I know it is insurance companies over there, but they do not like bad publicity either.  Get the pen out and start writing to everyone explaining your problem to them is a language they can understand.  Remember, they may not be medically minded so need it explained in simple form.
Give it a go, you have nothing to loose and everything to gain.

I know politics work in strange ways and even stranger over there, but someone might take up your fight.

Good luck with it.
I am NOT a doctor.  I try to help, but do not take what I say as medical advice.


Every journey, however large or small starts with the first step.

Sleep-well
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#7
RE: Limitations of AHI as a diagnostic tool
Oh, and if you have data already from a machine, send them that as well.
I am NOT a doctor.  I try to help, but do not take what I say as medical advice.


Every journey, however large or small starts with the first step.

Sleep-well
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#8
RE: Limitations of AHI as a diagnostic tool
Thanks, Sleep2Snore.
 That does seem like encouragement to be a sqeaky wheel...

My sleep apnea is rated moderate. I’ll be it would be diagnosed at a higher AHI if I spent the same amount of time in apnea, but with shorter events.


I maintain my protest that diagnosis revolves around AHI.
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#9
RE: Limitations of AHI as a diagnostic tool
What an interesting observation.

Although my empathy for your situation does not count as knowledgeable, I do empathize.

It is frustrating to have a problem that is uncommon, and be lumped and squished into the common mold without regard for the very thing that makes your case worthy of a little analytical thought. Even a moment of individualized attention has the potential to make a world of difference.

I am equally frustrated that my questions about the take home test ODI of 63.1, plus a rare-for-me breathing pattern (in which I wake up to discover that inhalation is not occurring automatically) happened to occur again earlier this month and is being completely disregarded as if it had not even occurred. When I mentioned that it was recorded by the machine, I got a dressing down about looking at the graphs. The response to the ODI was that the monitor must have fallen off; it was taped on! For all the freaking concern about the 'dangers' of adjusting my own machine, there has been NO concern whatsoever for the fact that a lack of inhalation woke me up. Um, helloooooooo. Are we unaware that No Air = No Life? Ugh. Sorry for the rant. I've been wanting to write and ask about these issues, but have had difficulty speaking to people ever since seeing that 2nd doctor for the first time. And now it just comes spilling out.
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#10
RE: Limitations of AHI as a diagnostic tool
(11-23-2017, 12:24 PM)kiwii Wrote: I am equally frustrated that my questions about the take home test ODI of 63.1, plus a rare-for-me breathing pattern (in which I wake up to discover that inhalation is not occurring automatically) happened to occur again earlier this month and is being completely disregarded as if it had not even occurred. When I mentioned that it was recorded by the machine, I got a dressing down about looking at the graphs. The response to the ODI was that the monitor must have fallen off; it was taped on! For all the freaking concern about the 'dangers' of adjusting my own machine, there has been NO concern whatsoever for the fact that a lack of inhalation woke me up. Um, helloooooooo. Are we unaware that No Air = No Life? Ugh. Sorry for the rant. I've been wanting to write and ask about these issues, but have had difficulty speaking to people ever since seeing that 2nd doctor for the first time. And now it just comes spilling out.

Kiwii, rant away!

Does your ASV address that issue, the one about involuntary breathing working incorrectly? I'm curious. That would no doubt make your AHI not reflect your degree of sleep disturbance.

Yeah, no fun at all to wake up not inhaling. I seem to have some apneas on inhale, but haven't at all addressed that concept yet. I have more of a problem not being able to exhale and then hyperventilating.

Anyway, my policy is to challenge assumptions no matter what the field, and linking AHI number with degree of sleep disturbance, IMO, is a troubling assumption, especially if you don't get taken seriously.

You are encouraged to share! You always provide insightful comments, and I'm sure many posters will want to reciprocate and offer support. I'm sorry your new sleep doc is being such a prig. You'd think you're saving him/her a whole lot of time, since you're willing to educate yourself and participate knowledgeably in your treatment.

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