AirFlow reduction ???

[Bobo97272]

90% of my AHI events are hypopneas. So I'm trying to understand how hypopneas are detected in my Airsence11 Autoset.

According to this:

The American Academy of Sleep Medicine (AASM) recommends that hypopneas be identified using a definition that is based on a ≥ 30% decrease in airflow,,,, ]

I'm feel sure that this is also the basis of Resmed's identification.
BUT a decease or reduction has to be measured by comparing, in this case, current airflow versus ..... what?
Is it the airflow of the breath immediately before the current breath, or some baseline value.
If it is some baseline, if so, how is that baseline determined or calculated?
Is it the previous 10 breaths or the breaths over some period of time?
Or something else?

*Understanding this would aid in evaluating a Hypopnea as a "real" or a false positives.

[ChicagoGranny]

*Understanding this would aid in evaluating a Hypopnea as a "real" or a false positives.

Unlikely.

Have a look at Figure 7 in Rubicon's comment on the first page of this thread - viewtopic/t186479/It-knows-when-you-are ... l-you.html It's an example of awake (or awakefulness) breathing.

There is another example in Pugsy's comment here --> viewtopic/t183656/DoeS-OSCAR-have-data- ... night.html

[Bobo97272]

*Understanding this would aid in evaluating a Hypopnea as a "real" or a false positives.

Unlikely.

Have a look at Figure 7 in Rubicon's comment on the first page of this thread - viewtopic/t186479/It-knows-when-you-are ... l-you.html It's an example of awake (or awakefulness) breathing.

There is another example in Pugsy's comment here --> viewtopic/t183656/DoeS-OSCAR-have-data- ... night.html

Thanks, but those comments seem to be addressing whether a person is awake (or semi-awake), aroused or not.
I'm interested in the identification criteria when asleep is sure and there are no abnormal breaths prior to the supposed hypopnea. (an example would be during a period of "periodic breathing")

[Bobo97272]

For example:

[palerider]

For example:

If that's one of yours, you've got way more problems than trying to figure out if a hypopnea is 'legit' or not.

[ChicagoGranny]

I wonder if Rubicon is interested in commenting?

[Bobo97272]

As an example: This Airflow identified, as a >30% reduction is compared with what segment of the preceding breaths

[palerider]

As an example: This Airflow identified, as a >30% reduction is compared with what segment of the preceding breaths

I don't see a tidal volume chart there.

[Bobo97272]

As an example: This Airflow identified, as a >30% reduction is compared with what segment of the preceding breaths

I don't see a tidal volume chart there.

Ahah, have I been looking at the wrong plot ?
Once I get a chance to , how far back do I need to look for the comparison segment?

[Bobo97272]

Do you see what I mean?
Is the comparison segment the prior 10 seconds, or 20 seconds, or 30 seconds or something else?

I'm assuming that the segment marked as hypopnea is averaging the volumes measured in that segment. In this case it would be max =477, min = 361 and the 2 sec average = 419

[Rubicon]

*Understanding this would aid in evaluating a Hypopnea as a "real" or a false positives.

Unlikely.

Agree, but WTH, suppose we need to talk about something (briefly anyway-- we should really be cooking or shopping!)

Anyway, and TTBOMK, the long-term (baseline) window is 100 seconds (excluding any apneas or hypopneas); the short-term window (event) is 8 seconds; the reduction criteria for a hypopnea is 50%; and flow imitation must be present in order to score a hypopnea.

[ozij]

*Understanding this would aid in evaluating a Hypopnea as a "real" or a false positives.

Unlikely.

Agree, but WTH, suppose we need to talk about something (briefly anyway-- we should really be cooking or shopping!)

Anyway, and TTBOMK, the long-term (baseline) window is 100 seconds (excluding any apneas or hypopneas); the short-term window (event) is 8 seconds; the reduction criteria for a hypopnea is 50%; and flow imitation must be present in order to score a hypopnea.

Rubicon is describing the real Resmed rules of identifying events.

They are not based on the latest AASM recommendations. Can't be - because of the long process of planning a machine, programming it and getting it certified.
Add to that the fact that the AASM is describing a sleeping person's breathing, and the machines don't take that into account.

[Bobo97272]

Anyway, and TTBOMK, the long-term (baseline) window is 100 seconds (excluding any apneas or hypopneas); the short-term window (event) is 8 seconds; the reduction criteria for a hypopnea is 50%; and flow imitation must be present in order to score a hypopnea.

Rubicon is describing the real Resmed rules of identifying events.

The "real" rules that Resmed applies is exactly what I was looking for. I'll have to go back to Oscar to collect the tidal volume values during the windows.

Parenthetically, I'd guess that the Resmed rules maybe more liberal* to account for the inability of Resmed machine to detect if the person were truely sleeping or not.
*liberal 50% versus 30% with respect to AASM guidance. But I never expected the Xpap device to ridgidly conform to AASM guides.

[Rubicon]

Parenthetically, I'd guess that the Resmed rules maybe more liberal*

Requiring 50% instead of 30% is actually "less" liberal.

[Bobo97272]

Yeah, I debated about “more restrictive” and “more liberal”, and decided it depended on the point of view. Regardless, we are understanding each other.
Per your suggestion, I’d best be doing some shopping and or cooking.
So…… Merry Christmas for now.