Is ResMed AHI Reporting always correct?

[SJ-Paddler]

Hi Guys:

I have been getting very good AHI averages from my current settings recently, 0.20 for the week. However when looking into OSCAR it does seem ResMed is not detecting all the Hypopneas. I am sure it is a programing thing which is very strict as opposed to subjective by a human.

See below. These look like Hypop events to you? 0.20 sounds great but I think the real number may be higher.

Just wondering what the rest of you think.

Thanks.

(For discussion purposes lets call Top Left #1 - Top Right #2 - Bottom Left #3 - Bottom Right #4)

[Pugsy]

Top left....awake/arousal breathing. Means nothing other than you weren't sound asleep.

As for the others kind of hard to tell with such short snippets BUT I think you are forgetting a very important part of the criteria needed for earning a flag and that's the amount of reduction in air flow or breathing.
That percentage of reduction that is needed along with the at least 10 second duration.
We have zero way to measure the amount of reduction in a percentage or the percentage that the sensors are picking up or not picking up.

I don't remember the minimum percentage of air flow reduction for a definition of hyponea from ResMed.
Back when I help Mark come up with the glossary of terms http://sleepyhead.sourceforge.net/wiki/ ... r_Glossary
It was 50% because I copied it from a ResMed document. This was years ago though and back when the S9 models were the latest and greatest. I don't know if the definition criteria has changed or not.

Also don't forget the requirement for a couple of recovery breaths along with the other criteria.

From eyeballing the other 3 snippets I would say that they don't amount to a 50% reduction (assuming that is still the parameter measurement to earn a flag) but that said....I have personally seen hyponea flags when I sit there wondering how in the hell they came up with that flag when I don't visually see any change in my flow rate.
And I don't see recovery breaths.....

So is the ResMed ALWAYS correct??? I don't think anything is 100% always right. There's always going to be a percent one way or the other for variances. No machine is ever going to be 100% perfect. Even when compared to in lab attended sleep studies there was a very small difference between human scored events and machine scored events....and humans can make mistakes as well.

Hypopnea

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)

[SJ-Paddler]

So is the ResMed ALWAYS correct??? I don't think anything is 100% always right. There's always going to be a percent one way or the other for variances. No machine is ever going to be 100% perfect. Even when compared to in lab attended sleep studies there was a very small difference between human scored events and machine scored events....and humans can make mistakes as well.

Thanks Pugsy, maybe I am just watching too many YouTube experts. I saw one from Australia who seemed to imply these changes were all missed Hypop, sorry forget actual video. Wasn't Lankey. In any case you made me feel better about my results, thought they were too good to be true.

[Pugsy]

maybe I am just watching too many YouTube experts.

Humans have their opinions about stuff...the guy in Australia or Jason (LankyLefty) or our own sleep study retired RT here on the forum who recently has come back here to voice his opinion.... are just humans with opinions that happen to voice them in a manner that alludes to being "expert" but in the end they are just humans voicing their opinion.
They don't walk on water...they possibly could be wrong about something because humans are not perfect either.

I prefer to form my own opinion whenever I can based on my own education and personal experience. Am I always right??
Hell no...and I will be the first to admit it. I am far from perfect.

Let me ask you a question about those (in your eyes or the guy in Australia with the you tube stuff) results that might point to hyponeas not flagged....what are you going to do about them anyway??? Does anything need to be done about them anyway???
We all have arousals in our sleep...it's normal to wake after REM anyway...we may or may not remember those arousals.
What are you going to do about them???
We don't breathe or sleep the same all night long in terms of actual flow rate or breaths. We dream, we change position in bed, we do all sorts of things while in bed that could affect what the flow rate shows but it isn't necessarily related to some sort of apnea event. Yes, sometimes it is but we forget that there's a lot more to sleep quality than just what the airway does or doesn't do. We expect the machine to work miracles and fix problems it simply can't fix.....and forget that nothing is perfect. Nothing is 100% right about everything 100% of the time.

The answer to all our sleep problems (or not feeling the nice low AHI problem) isn't always available by putting each breath under the microscope and blaming the machine for not flagging something.

The reason the machine doesn't flag something is because some part of the criteria for a flag is missing.....at least per what the machine is sensing. Is the machine always right??? Nothing is life is 100% absolute and the quicker we accept that fact the quicker we can reduce or stress load...and the quicker we can learn to roll with the flow and accept that nothing is perfect.

We can see poor sleep quality on the flow rate but we can't always see what is causing the poor sleep quality....no matter how much we might try.

[Dog Slobber]

I don't think you can make the determination that ResMed's reporting of Hyponea's is incorrect, especially based the provided diagrams.

• There isn't a universal definition of what defines hypopnea, a causal google search reveals values between 30-50%
• The drop in flow rate is compared to a previously determined average, but how long is the sample size to determine that average? That too is unknown.
• Your snippets don't show much of the breaths leading up to your alleged missed hypopneas
• With your snippets, there does appear to be a drop in flow-rate. We simply can't determine how much of a flow-rate reduction there is, nor the criteria.
• We also can't easily tell the start/end of the hypopnea period, this is important because the minimum period is 10 seconds.
• OSCAR graphs (dependent on Scale and Size) simply don't have the granularity to eye-ball accurately
• We may be pretty good at comparing relative amplitude of the flow-rate wave, we are not very adept at relative comparisons of the frequency. Breathing frequency as well as force is graphed but that's not easy to visually compare.
• Many of the above mentioned constraints go away with actual numbers to do math on.

Some might argue that there is motivation for CPAP manufacturers to deliberately under report flagged events, so there machines appear to perform better. But given one of the criteria for adjusting pressures is based on these events, the end therapy would be poorer performance and that would show up as well.

[AndyB]

Pugsy -- your last post in this thread is terrific . . . just spot on. Thanks for always thoughtful insights.

[dataq1]

Some might argue that there is motivation for CPAP manufacturers to deliberately under report flagged events, so there machines appear to perform better. But given one of the criteria for adjusting pressures is based on these events, the end therapy would be poorer performance and that would show up as well.

My cynical self would argue the opposite, the manufacturers may have a tendency to over report events, as it supports continued use and sales.

Now there is an interesting discussion over at viewtopic/t184600/New-sleep-study-resul ... 5#p1415025 wherein Rubicon makes the case that

Hypopneas require an arousal and/or a desaturation to be scored as such

and Tec5 points out

As most home equipment (Dreamstation/Airsense) does not identify arousals or desaturations, the scoring of hypopneas as reported in OSCAR reports would not qualify as a hypopnea by AASM standards, Is that correct?

So that thread is waiting for a reply from Rubicon.

Actually there is an accepted definition of a hypopnea:

The “recommended” hypopnea definition (H3A) in the current version of the AASM Scoring Manual defines a hypopnea in adults based on a ≥ 30% drop in airflow for ≥ 10 seconds associated with an arousal or a ≥ 3% oxygen desaturation.(May 1, 2022)

As to Dog's additional point.... a 30% drop in airflow (presumably based on airflow occurring previously over some unknown period of time) I just don't know what period of time Resmed uses, nor have I discovered what time period AASM might suggest.

As to the granularity of the Resmed that is well known, and OSCAR (I believe) plots all the datapoints.

[palerider]

Some might argue that there is motivation for CPAP manufacturers to deliberately under report flagged events, so there machines appear to perform better. But given one of the criteria for adjusting pressures is based on these events, the end therapy would be poorer performance and that would show up as well.

My cynical self would argue the opposite, the manufacturers may have a tendency to over report events, as it supports continued use and sales.

You've got that exactly backwards. The sale has already been made at the time a patient is using a machine at home.

[dataq1]

My cynical self would argue the opposite, the manufacturers may have a tendency to over report events, as it supports continued use and sales.

You've got that exactly backwards. The sale has already been made at the time a patient is using a machine at home.

I did say continued use and sales.
Continued use as seen in some folks who are fixated on chasing “better” numbers. Add on sales as folks look to improve numbers by purchasing alternate masks etc in an effort to move their AHI from (say) 2.5 to some lower self imposed goal .