Question about hypopneas

[Timur]

I'm very confused about the different standards used to identify hypopneas.  

Apparently different labs use different criteria and this is permitted under AASM guidelines.

http://www.aasmnet.org/articles.aspx?id=4203

I was very surprised to learn this, and saw one example on another forum where someone had an AHI of less than 5 under one set of guidelines (used by Medicare) and yet was scored as having moderate OSA according to the recommended AASM guidelines. Quite a difference!

Then, I recently found out that two of the biggest makers of XPAP devices base their determination of an hypopnea on different criteria as well:

"An hypopnea is indicated if there is approximately 40% reduction in airflow for a duration of between 10 and 60 seconds, compared to the average airflow over an extended period of several minutes. Following a reduction in airflow, the therapy device must see two recovery breaths in order to label the event as a potential hypopnea. (Respironics detection is 40% reduction and ResMed detection is 50% reduction)"


So their standards are different and lower than those used the AASM requiring a 30% reduction in airflow to qualify and be scored as an hypopnea. 

For those of us who have been diagnosed using the 30% definition if these events are not being reported, are they being adequately treated? 

Thanks for any input on this, and i am hoping that I have misunderstood something in all of this that can easily be clarified. 

I have to report that CPAP has worked wonders for me so whatever it is doing, it is working in my case, but I am curious about this.

[HalfAsleep]

I was the one diagnosed with moderate SA with an AHI of 18, but an AHI of 5 on the Medicare standard.

The Medicare rules are not very straightfoward, but have to do with oxygen desat and co-existing conditions. I believe I posted the Medicare rules. If not, I can fish them out.

I had a lot of hypopneas....

[Timur]

Thanks for your reply! I must say that reading about your results was quite a surprise and even a bit of a shock. I thought there would be a uniform standard when it comes to diagnosing and treating SDB/OSA. 

I was diagnosed in Canada in an overnight sleep study  and all my events were hypopneas. 

My sleep study simply states that  "AASM Version 2.2 (adopted in 2015) was used for scoring events. Who knows if they used the "recommended" or the "acceptable" standard set out by AASM. To me the two are worlds apart and as a patient I would like to know which interpretation was used.

I have to say that reading all of this has made me a bit jaded about the "science" of sleep medicine. 

The definition seems to change depending on who is financing the treatment. This seems so wrong to me. How can it even be called science?

[Margali]

Nevermind, I need more coffee.

[PaytonA]

If I remember correctly the definition for a hypopnea stipulates flow reduction between 30% and 50%. The sleep test scoring has chosen 30% but could choose 50%.

[Timur]

I found a rather interesting article discussing the definition of hypopneas published in the December 2015 issue of the journal "Sleep" 

https://www.ncbi.nlm.nih.gov/pmc/article...;=activity

"The classification of obstructive sleep apnea (OSA) severity in a population of more than 6,400 individuals was affected by the metrics employed for estimating hypopneas. Indeed, among the individuals classified as suffering OSA (AHI ≥ 5 per hour) the distribution among severity categories (mild, moderate, or severe) varied considerably. Most strikingly, however, is that the percentage of individuals classified as normal were 48%, 30%, or 17% of the population under study, depending on the hypopnea metrics employed. In other words, almost one-third (31%) of the investigated subjects could be moved from normal to OSA labels or vice versa. Moreover, the proportion of moderate (15 ≤ AHI < 30 per hour) and severe (AHI ≥ 30 per hour) OSA changed as much as 13.5% and 10%, respectively, depending on the hypopnea definition used."

[Crimson Nape]

Timur,
If you wish to see what is occurring at a 50% reduction rate, or any value you wish. go to File->Preferences->CPAP. Place checkmark in the Custom CPAP User Event Flagging. In Events tab check the UserFlag1 and UserFlag2. You can change the display name for these by changing the Label entries.

[Timur]

Thanks Payton and Crimson Nape for your replies.

I changed my User Event Flagging in SH to reflect a 50% and  a 30% airflow reduction rate, and am very pleased to see that my hypopnea index is just fine. A bit higher than reported but way, way less than 5, usually closer to 1. 

 I must admit that I figured this would be the case because I feel absolutely wonderful on CPAP. It has transformed my life.

[HalfAsleep]

Thanks for your reply! I must say that reading about your results was quite a surprise and even a bit of a shock. I thought there would be a uniform standard when it comes to diagnosing and treating SDB/OSA. 

I was diagnosed in Canada in an overnight sleep study  and all my events were hypopneas. 

My sleep study simply states that  "AASM Version 2.2 (adopted in 2015) was used for scoring events. Who knows if they used the "recommended" or the "acceptable" standard set out by AASM. To me the two are worlds apart and as a patient I would like to know which interpretation was used.

I have to say that reading all of this has made me a bit jaded about the "science" of sleep medicine. 

The definition seems to change depending on who is financing the treatment. This seems so wrong to me. How can it even be called science?

I'm glad for your follow up (I had to go to work, so I couldn't give a more lengthy reply above).

After I got my AHI numbers, AHI=18 and CMS AHI=5, I couldn't make any sense of it either. Any of it, the diagnosis, the non-Medicare coverage...

So I started digging. Now it makes a lotta sense.


These are the definitions, right off my sleep test report...

AHI: Includes all apneas & all hypopneas associated with an arousal or a ? 3% desaturation. 
CMS AHI: Includes all apneas & only hypopneas associated with a ? 4% desaturation. 

Almost all of my events were between 3% and 4% O2 desat.
5 per hour were > 4% desat

So, I have significant apnea, just not a large dip in O2 per event. As a footnote here, my O2 went as low as 85%.

In other words, the classification of hypopneas is in fact data-driven.

Here are the Medicare specs:
https://www.cms.gov/Outreach-and-Educati...905064.pdf

I've attached a screen shot of the section where the Medicare guidelines specific to AHI are. For Medicare, the operative numbers are what my sleep study categorizes as CMS AHI.

I hope this helps sort out the hypopnea definitions, AHI determination, and how treatment is qualified.

And yes, per discussion with the sleep doc after my original post, I qualify for Medicare coverage for treatment (the specs cited above are 2016, and Medicare lowered the AHI bar by .1).

[PaytonA]

It may be my failing eyesight but I could not find any Medicare specs for scoring hypopneas at that link.

Best Regards,

PaytonA