Hypopnea Scoring - The Difference Between This and That

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Hypopnea Scoring - The Difference Between This and That

Postby themonk » Wed Aug 08, 2012 10:15 am

I am prepping for an ENT surgeon visit this week by reviewing my two sleep studies from earlier this year in detail. I have the raw data from the Rembrant Analysis Management tool so I can see essentially what the doc sees.

Some very interesting data sprinkled throughout. One thing that I glossed over when I initially reviewed them a few weeks ago is a field that lists the number of desats >=4%.

Quick background: I was listed at 74 total hypopneas, no apneas, no snoring, no limb movement. My O2 avg was 95.x% w/ the lowest reading at 90.x%. For some reason, the number of desats >=4% is listed at 11 for the night.

For reference, I had no apneas during my titration study either, only a few hypopneas.

I was working under the assumption that hypopneas had to have a desat of 4% to be counted, which I thought was the 'recommended' method. It actually says that on the sleep tech check-in sheet, which I also have. It appears from the report that the lab used the 'alternative' or perhaps both to get to the 74 number. I am not sure how to reconcile the two numbers - 74 vs 11.

This is actually pretty important in my case because it means the difference between and AHI of 24 (which is what was reported) and an AHI of 4.3.

Anyone have any insight into why these numbers would vary so widely? Shouldn't the number of desats roughly match the number of hypopneas?
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Re: Hypopnea Scoring - The Difference Between This and That

Postby robysue » Wed Aug 08, 2012 5:50 pm

Scoring of hypopneas on NPSGs is, unfortunately not uniform. The sleep docs diagnosing us with SDB all believe hyponeas should be counted---or at least some hypopneas should be counted, but which ones should count still seems to be a bone of contention. Which is why we've got the confusing mess of the American Academy of Sleep Medicine (AASM) having two official definitions for scoring hypopneas: The AASM Recommended Standard and the AASM Alternative Standard for hypopneas. See http://www.ncbi.nlm.nih.gov/pubmed/19238801 and http://www.journalsleep.org/ViewAbstract.aspx?pid=27368 for a scholarly discussion of how and when these two standards affect a patient's diagnosis of OSA as well as the formal definitions of the two standards:

AASM Recommended Standard: A hypopnea requires at least a 30% reduction in airflow for at least 10 seconds AND a corresponding O2 desaturation of at least 4%. Such a hypopnea does NOT require an EEG arousal

AASM Alternative Standard: A hypopnea requires at least a 50% reduction in airflow for at least 10 seconds AND one or both of the following conditions: A EEG arousal OR a corresponding O2 desaturation of at least 3%.

Of course, under both standards, the hypopnea has to occur during an epoch when the patient is ASLEEP according to the EEG evidence.


It's my understanding that Medicare requires hypopneas to be scored under the AASM Recommended standard, but that the folks working in sleep medicine are increasingly leaning towards believing that the arousals triggered by large numbers of "Alternative Standard hypopneas" can be just as damaging to the body as the O2 desats triggered by the hypopneas scored under the Recommended Standard. And it's also my understanding that some sleep doctors (such as mine) are deeply concerned that Medicare insists upon a 4% desat to score an hypopnea.

So my best guess is that your lab, like the lab where my diagnostic PSG was done, uses both rules, but distinguishes between them in the data. I've never seen my raw data--I had no luck in getting that released to me. But on the full summary report all of my hypopneas were listed as "hypopneas with arousal" (i.e. Alternative standard) and did not got into the computation of my (Medicare) AHI. In my case, I had a handful of OAs on that study, so my AHI was listed as 3.5, not enough to get an OSA diagnosis by Medicare standards. But with the 75+ hypopneas with arousal, my RDI = 23.1, and that got me formally diagnosed with moderate OSA because either the RDI or the AHI can be used to diagnose OSA. And my insurance company was perfectly willing to cover the cost of my treatment based on that study.
current settings Min EPAP = 4, Max IPAP = 8 and Rise time = 3

8/1/2010 sleep study results:
AHI = 3.9 [AHI = (#OA +#CA + #H w/desat) per hour]
RDI = 23.4 [RDI = (#OA +CA + #H w/desat + #H w/arousal) per hour]
Dx: Moderate OSA
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Re: Hypopnea Scoring - The Difference Between This and That

Postby themonk » Thu Aug 09, 2012 8:28 am

Thanks RobySue! Great information and very helpful. You are correct, my lab uses essentially both. Had they selected the recommended alone, I wouldn't have apnea. It sure seems the world of hypopneas needs to be thoroughly researched and some kind of determination needs to be made.

Just seems a shame to saddle people with a life-long disorder when you actually may or may not have it.
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Re: Hypopnea Scoring - The Difference Between This and That

Postby robysue » Thu Aug 09, 2012 1:21 pm

themonk wrote:It sure seems the world of hypopneas needs to be thoroughly researched and some kind of determination needs to be made.

Just seems a shame to saddle people with a life-long disorder when you actually may or may not have it.

From what I've read and from my conversations with my sleep doc, the problem seems to be Medicare's insistence on using the "old" standard that treats arousals as "unimportant." But there's increasing evidence that the repeated arousals (and the adrenalin and cortisol that gets pumped into the body with each arousal) are as damaging to the body as the O2 desats from the older "Recommended" standard. And those repeated arousals are certainly as disrupting to the sleep cycles as the O2 desats are.
current settings Min EPAP = 4, Max IPAP = 8 and Rise time = 3

8/1/2010 sleep study results:
AHI = 3.9 [AHI = (#OA +#CA + #H w/desat) per hour]
RDI = 23.4 [RDI = (#OA +CA + #H w/desat + #H w/arousal) per hour]
Dx: Moderate OSA
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Re: Hypopnea Scoring - The Difference Between This and That

Postby themonk » Fri Aug 10, 2012 9:46 am

It almost seems they need another metric added to the analysis - one that considers the length and depth as part of the official diagnosis. Arousals happen for any number of reasons. I actually had many more arousals unrelated to breathing during my extremely horrible sleep study. I also had more RERA's than hypopneas.

If they could narrow down the diagnosis, it might give people more tailored treatment options than basically giving 100% of people PAP machines. They very well may not be the most optimal treatment for some.

I guess that might be too much to ask at this point. Much easier for the doc to let Rembrant score the sleep study with no additional evaluation, assign a PAP machine, rinse, repeat and hope that the patient either gets lucky w/ a PAP machine or gives up and just goes away.
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Re: Hypopnea Scoring - The Difference Between This and That

Postby a.b.luisi,d.m.d. » Sat Aug 11, 2012 2:47 pm

themonk wrote:Thanks RobySue! Great information and very helpful. You are correct, my lab uses essentially both. Had they selected the recommended alone, I wouldn't have apnea. It sure seems the world of hypopneas needs to be thoroughly researched and some kind of determination needs to be made.

Just seems a shame to saddle people with a life-long disorder when you actually may or may not have it.

You see, part of the problem is that you can't just focus on the number of oxygen desaturations. Any time you get an EEG arousal, that can break up your sleep cycle. You can feel lousy because you have a fragmented sleep cycle even when your oxygen desats. aren't that bad. That is why people with UARS can be symptomatic, even though they have no official apneas or hypopneas.
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Re: Hypopnea Scoring - The Difference Between This and That

Postby themonk » Mon Aug 13, 2012 9:36 am

a.b.luisi,d.m.d. wrote:You see, part of the problem is that you can't just focus on the number of oxygen desaturations. Any time you get an EEG arousal, that can break up your sleep cycle. You can feel lousy because you have a fragmented sleep cycle even when your oxygen desats. aren't that bad. That is why people with UARS can be symptomatic, even though they have no official apneas or hypopneas.


Thank you Doc. Arousals happen for any number of reasons, especially in the atypical night of sleep in a sleep lab, but your ponit is well taken and I truly appreciate your involvement on this forum.

Sleep medicine is still an emerging science and should be treated as one in my opinion. Sleep docs may present the results as unequivocal, but they should be questioned heavily. A PSG is not perfect and there are any number of reasons to respectfully ask deep questions to fully understand your very unique set of health issues and determine the proper treatment. Anyone who believes their doctors to be perfect or working in their best interest deserve what they get, I am afraid. You must become an expert. This goes for anything where your well-being is secondary to some competing factor (such as a doctor's time, patience, money, greed, incompetence).
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