How to match my numbers to dx?

Assuming that the following is correct (I grabbed it from another thread):

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%.

I'm looking at my sleep study report and trying to figure this out. My oxygen did drop, but it seems to have been not far and not for long. Is there any way to get from my numbers to the resulting diagnosis?

The lab's gonna use the standard the lab's gonna use. And base the diagnosis on the computed AHI and/or RDI using whichever standard the lab's decided to use. And the diagnosis lines seems to be the same regardless of the choice of standard for scoring hypopneas:

AHI/RDI < 5: No apnea
5 <= AHI/RDI < 15: Mild OSA
15 <= AHI/RDI < 30: Moderate OSA
30 <= AHI/RDI: Severe OSA

The report is supposed to indicate which standard is being used to score the hypopneas, but that info may be hard to find (fine print) or simply omitted altogether. And to tease it apart, you need the full data and summary graphs, not just the doctor's dictated interpretation.

Some hints: Are hypopneas split into two types? Those "with arousal" and those "with desaturation"? Is there a written explanation of what goes into the computation of the AHI vs the RDI?

So the bottom line is this: You may have to ask the sleep doc who dictated the interpretation the question directly: Which standard was used to score the hypopneas? And why is that the choice you and your lab make?

Jade wrote:I'm looking at my sleep study report and trying to figure this out. My oxygen did drop, but it seems to have been not far and not for long. Is there any way to get from my numbers to the resulting diagnosis?

How far and how long? Because any drops below 90% are clinically significant if I recall correctly. (Unless it was written off as "bad" data because the O2 monitor came lose on your finger or fell off altogether, which happened a number of times during my four different sleep studies.)

For additional help in parsing the meaning of all those numbers, you might want to read my post Understanding the data in your sleep test report

The hypop. rule is listed as "4B"--is this the standard?

I have what appears to be the full report; over a dozen pages of tables, charts, and graphs.

Hypops are categorized by body position. There's numbers for resp. events, arousals, and oxygen sat's. But I don't see those last three correlated with hypops.

Why do the different standards exist? What does it mean if someone "qualifies" under one standard but not another? I'd like to think there's a non-cynical reason that's the basis for choosing one standard over another.

2% of my total sleep time was apparently between 80-89%; the lowest it went.

Ask the doctor (maybe the DME?) what your diagnosis is. It should be on the doctor's dictated report. I think it would be impossible to figure out from the information from the lab.

I know what my dx is. What I don't understand is how it was arrived at with what seems to me minimal accompanying desat's, though admittedly a high hypop. index (no apneas, apparently).

Do they usually require O2 drop or EEG to score apneas, or simply base them on flow waveforms?

Jade wrote:The hypop. rule is listed as "4B"--is this the standard?

4B is the AASM Alternate Standard for hypopneas. It 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%.

So your airflow dips by 50% or more for at least 10 seconds and then there's an EEG arousal at the same time the reduced airflow ends, that counts as a "hypopnea" under 4B even if there is NO O2 desat at all. If your sleep study shows very few or no O2 desats, then you can pretty much assume that most of your H's on the sleep study were hypopneas with arousal under the 4B rule.

And yes, rule 4B is an accepted standard for diagnosing OSA---except for Medicare patients. Medicare requires the scoring of hypopneas to be done using rule 4A---the "AASM Recommended Standard". In other words, Medicare insists on a 4% O2 desat before a hypopnea can be scored.

Hypops are categorized by body position. There's numbers for resp. events, arousals, and oxygen sat's. But I don't see those last three correlated with hypops.

The hypops should be PART of the resp. events total. Other things that get added to resp. events include OAs and CAs. If the lab measures them, RERAs get thrown into the resp. event totals.

An arousal is any sudden shift in the EEG from a deeper stage of sleep to a lighter stage (or all the way to WAKE). Any hypopnea that was scored under rule 4B because it had a corresponding arousal will be part of the arousal count. OAs and CAs will count towards the arousal numbers---if they ended with an EEG arousal. But resp. events that did not actually trigger an arousal won't count towards the arousal number. The only resp. events that "count" toward the O2 desat numbers are those events that had a clinically significant O2 desat associated with them. Since the lab is using rule 4B, my guess is that a 3% drop in O2 levels counts as an O2 desat. Those hypops scored under rule 4B because they had an associated arousal, but no desat, are not going to be part of the O2 desat numbers.

Why do the different standards exist? What does it mean if someone "qualifies" under one standard but not another? I'd like to think there's a non-cynical reason that's the basis for choosing one standard over another.

I wish I knew for sure. I asked my new sleep doc that in June. She said something along the lines that Medicare requires the rule 4A standard. But since the time Medicare set that standard many years ago, there's been increasing evidence that the repeated arousals associated with SDB are clinically significant all by themselves---i.e. the repeated adrenaline rushes (from each time you arouse) can cause health issues all by themselves and the arousals obviously play havoc with our ability to get into slow wave sleep and REM sleep, both of which are needed for the body to properly repair itself during sleep. In my case, I would NOT have qualified for a CPAP had I been covered by Medicare rules: My Medicare AHI on the diagnostic test was a mere 3.5, well below the required cutoff. But my RDI which included the hypops scored under rule 4B was 23.1, well into the Moderate OSA range. My doc said that had I been covered by Medicare, she would have fought for coverage by filing the necessary paperwork for the appeal since she's one of the docs who does believe that the large number of arousals are problems all by themselves.

My own take from reading what I can at the AASM site is that when the rules were revisited and revised, rule 4B was adopted as a valid standard because so many of the AASM members had been persuaded by the evidence that hypopneas with arousal really are part of OSA and need to be treated, but Medicare was the elephant in the room and would not budge on changing its standards for deciding when to cover CPAP equipment for patients. And the result is the royal mess we have now with two different standards for scoring H's.

2% of my total sleep time was apparently between 80-89%; the lowest it went.

My understanding is that ANY time under 90% is signficant. The lowest my O2 dropped during my diagnostic test was 91%.

archangle wrote:Do they usually require O2 drop or EEG to score apneas, or simply base them on flow waveforms?

I believe that on a NPSG, to score an apnea, they are looking at a FLAT LINE (or very close to a FLAT LINE) on the flow waveform for at least 10 seconds that starts during an epoch scored as SLEEP. So the EEG is used to determine whether you were asleep when you stopped breathing. If the epoch is scored as WAKE, I don't believe it gets counted as an apnea. To distinguish between an OA and a CA, they are looking at the corresponding data from the belts around your chest and abdomen that measure effort to breathe.

robysue, thanks for sharing the efforts of your research. There's not really any reported info about EEG arousals in my report, but my dr did say there were a lot of "alpha intrusions" in my sleep during periods it should have been delta waves.

I read a bit about that. It seems that drs can measure it and see it's a different pattern than "normal" sleep for "normal" people. However, they don't really understand the connection between alpha waves and hypop's (or apneas). And they haven't yet figured out either whether there's any correlation between them. That was my take-away, anyway.

While I recall more brief awakenings when I get up in the morning than most people usually report, it's not nearly so many as the lab measured, of course.

Further, while my subjective experience included slightly more and slightly longer (though still pretty brief) awakenings, it hardly seemed enough to warrant the nose-dive my daytime functioning took. It was not insomnia though I did institute a stricter sleeping regime in an effort to help the situation. This happened during two separate three-month-long periods of 100% cpap adherence. Things were getting steadily worse on a weekly basis, until I was literally becoming a danger to myself and had to cease use.

Since I haven't heard of any medical practitioners who've had reasonably repeatable success reducing alpha intrusions, and cpap itself apparently didn't help that before I reached a critical, deal-breaking point, I'm caught in a Catch-22 circumstance. Although, I don't know for a fact what, if any, role the alpha intrusions play. I could be waking up from the cpap itself, though I tend to doubt that for several reasons.