Baseline for Desaturations and Flow rates

robysue1 wrote: ↑

Thu Dec 08, 2022 5:01 pm

Yes, Wondering is talking about oxygenation.

Firstly, I want to say that I am interested in this topic of hypopneas and desaturations, and I really appreciate that you have taken the discussion seriously (not resorted to cartoons and drive by cryptic comments).

When I began this topic my interest was on hypopneas and desaturations, but it seems it has now evolved into a discussion of respiratory effort and how that is measured, particularly with home XPAP machines. I did read the article that you posed to Wondering, and it was all about flow limitations and proposed methods to "measure" flow limitations. (Short of the gold-standard esophageal pressure - UGH- not in my bed). So it was interesting, and pertinent to an overall discussion of sleep disordered breathing, but not necessarily to oxygenation, the original topic of this thread.

Regardless, there was one thing that did catch my eye and that was the assertion that Resmed requires a flow limitation to be observed in order to flag a hypopnea. So I looked through last night OSCAR to find that association.


Well not only did I not find a flow limitation associated with the H flag, I suspect that PR would classify these breaths as being dogsh*t because of their shape. I can see why PR might see these shapes as taking extra "effort", BUT that "extra effort" does not seem to be detected by the Flow Limitations chart. BTW, I also checked the 0-1 scale just to be sure that the flow limitation wasn't greater than 0.25, and nope, nothing there.

Well, this is a bit off track from the original thread topic,

Tec5 wrote: ↑

Thu Dec 08, 2022 10:16 pm

robysue1 wrote: ↑

Thu Dec 08, 2022 5:01 pm

Yes, Wondering is talking about oxygenation.

Firstly, I want to say that I am interested in this topic of hypopneas and desaturations, and I really appreciate that you have taken the discussion seriously (not resorted to cartoons and drive by cryptic comments).

When I began this topic my interest was on hypopneas and desaturations, but it seems it has now evolved into a discussion of respiratory effort and how that is measured, particularly with home XPAP machines.

Home xPAP machined do not, cannot measure breathing effort.

Regardless, there was one thing that did catch my eye and that was the assertion that Resmed requires a flow limitation to be observed in order to flag a hypopnea. So I looked through last night OSCAR to find that association.

Severe limitations in flow limitations can be observed in the image you uploaded.

Well not only did I not find a flow limitation associated with the H flag,

I wonder why you didn't observer how badly limited the flow was in those hypopneas.

zonker wrote: ↑

Thu Dec 08, 2022 5:07 pm

Rubicon wrote: ↑

Thu Dec 08, 2022 4:42 pm

Rubicon wrote: ↑

Thu Dec 08, 2022 4:31 pm

zonker wrote: ↑

Thu Dec 08, 2022 3:59 pm

Rubicon wrote: ↑

Thu Dec 08, 2022 3:33 pm

But after a while--

the comments just beat you down...

which is the whole point.

That it's all hopeless?

And the terrorists won?

No really, what's your point?

ozij wrote: ↑

Thu Dec 08, 2022 10:49 pm

Severe limitations in flow limitations can be observed in the image you uploaded.

TTBOMK, the algorithm only needs one FL to score a hypopnea.

And there is, in fact, one scored FL in that image.

At the very beginning:

robysue1 wrote: ↑

Thu Dec 08, 2022 5:01 pm

Yes, Wondering is talking about oxygenation.

Not finding that. Only Tec5 mentioned it in Post #1 and then things took a different direction.

Rubicon wrote: ↑

Fri Dec 09, 2022 12:17 am

ozij wrote: ↑

Thu Dec 08, 2022 10:49 pm

Severe limitations in flow limitations can be observed in the image you uploaded.

TTBOMK, the algorithm only needs one FL to score a hypopnea.

And there is, in fact, one scored FL in that image.

Bad editing on my part.

I meant to say

severe limitations in flow can be observed

Rubicon wrote: ↑

Fri Dec 09, 2022 12:23 am

At the very beginning:

Are you referring to the 4% (0.04) that was reported 20 seconds before the H flag.

Firstly, a 4% (of some undefined scale) maybe background noise, and secondly it's occurring well before the hypopnea evaluation interval (10 seconds).

ozij wrote: ↑

Fri Dec 09, 2022 5:13 am

Rubicon wrote: ↑

Fri Dec 09, 2022 12:17 am

ozij wrote: ↑

Thu Dec 08, 2022 10:49 pm

Severe limitations in flow limitations can be observed in the image you uploaded.

TTBOMK, the algorithm only needs one FL to score a hypopnea.

And there is, in fact, one scored FL in that image.

Bad editing on my part.

I meant to say

severe limitations in flow can be observed

I'd agree, that flow disturbances are clearly observable, but Resmed algorithm apparently did not see those disturbances, so they did NOT report them as being flow limitations.

Rubicon wrote: ↑

Fri Dec 09, 2022 12:33 am

robysue1 wrote: ↑

Thu Dec 08, 2022 5:01 pm

Yes, Wondering is talking about oxygenation.

Not finding that. Only Tec5 mentioned it in Post #1 and then things took a different direction.

You're right about that. Wondering1 hasn't been talking about oxygenation. He's been pushing using TV as a criteria for scoring hypopneas.

I shouldn't have conceded that point to Tec5.

As for:

Tec5 wrote: ↑

Thu Dec 08, 2022 10:16 pm

Regardless, there was one thing that did catch my eye and that was the assertion that Resmed requires a flow limitation to be observed in order to flag a hypopnea. So I looked through last night OSCAR to find that association.


Well not only did I not find a flow limitation associated with the H flag,

As others have pointed out, there's a flow limitation scored right at that first breath and the shapes of all three of these breaths leaves one wondering why there is not more activity in the flow limitation graph. And, my guess is the breath that immediately precedes the first breath in the snippet is not only flow limited, but also quite likely part of the hypopnea. There's got to be a reason Tec5 didn't include a few more breaths that are clearly before the beginning of this hypopnea.

Finally I want to address this comment of Tec5's:

Tec5 wrote: ↑

Thu Dec 08, 2022 10:16 pm

Well, this is a bit off track from the original thread topic,

I answered your question about baseline oxygenation with respect to scoring on formal sleep tests in this post way back on page 1.

Since xPAPs do not measure oxygenation, they cannot use O2 desats as a scoring criteria for flagging a stretch of breathing as a hypopnea.

Yes, this thread has gotten off the original topic. That's specifically because of questions posed by Wondering1 early in the thread:

• Back on page 1 Wondering1 in this post, Wondering1 posted a hypopnea with the question, "So how is this a hypopnea"?
• Wondering1 then posted the data a second time in in this post along with introducing his/her pet idea that "But my main question is this..... when examining these charts for hypopneas, should the tidal volume chart be used for guidance?" At this point I and Rubicon answered his basic question of why the hypopnea had been scored. And I made the argument that TV is simply not used by the professionals in sleep medicine.
• Rather than accepting that TV is not used by the professionals as a criteria for defining hypopneas, Wondering1 has continued to chime in on why TV should be used. Along the way, he also posted misleading information about what flow is and he questioned whether the data presented in the graph Oscar labels Flow Rate is the "flow" used in the ResMed definition for scoring hypopneas.
• Actual screen shots of Resmed documents that specify the criteria for flagging events was posted by Rubicon back on page 3. And yet, Wondering1 has continued to claim that TV should be used when looking at hypopneas scored by xPAP machines.
• And now Tec5 has also chimed in that "flow limitation" is not used as part of Resmed's algorithm for scoring hypopneas, when in fact it is and Resmed specifically says that it is used.

robysue1 wrote: ↑

Fri Dec 09, 2022 10:19 am

And, my guess is the breath that immediately precedes the first breath in the snippet is not only flow limited, but also quite likely part of the hypopnea.

The breath that was snipped (that apparently is associated with the a 0.04 flow limitation occurred 20 seconds before the hypopnea flag.
It's quite reasonable to use all the data in the 10 second interval for evaluating a hypopnea event, but to go back to an observation of data well in advance is unreasonable.

How far back in time do you folks want to go?

The the period this hypopnea flag should be examining should be from 01:09:10 to 01:09:20, not something that happened ten seconds sooner. (or do you disagree?)

(I guess an alternative theory might be that the hypopnea detecting algorithm takes more than ten seconds to decide)

ozij wrote: ↑

Thu Dec 08, 2022 10:49 pm

Home xPAP machined do not, cannot measure breathing effort.

I quite agree, however the focus of the paper that robysue1 posted quite a while back was to the effect that "flow limitations" can/might be used in lieu of belts or esophageal sensors to detect effort.

Correct or not, it seems that Resmed's "flow limitations" grading is being used to monitor or indicate breathing effort.

robysue1 wrote: ↑

Fri Dec 09, 2022 10:19 am

Resmed specifically says that it is used.

OK, I missed where Resmed specifically says that FL is used to establish a hypopnea.
Is that somewhere in this thread ?

All I can see looks like a hiccup.

Tec5 wrote: ↑

Fri Dec 09, 2022 10:11 am

Firstly, a 4% (of some undefined scale) maybe background noise, and secondly it's occurring well before the hypopnea evaluation interval (10 seconds).

After careful consideration, I have come to the conclusion that you are so fucking stupid as to boggle the imagination.