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Rubicon wrote: ↑

Sat Dec 03, 2022 11:39 am

robysue1 wrote: ↑

Fri Dec 02, 2022 9:14 pm

That the big one or the little one?

The little one.

Clearly gonna need the big one:

pfft, that thing ain't gonna do it. you need something bigger



(might need to go with the 10 pounder, on second thought.

Perhaps a Tombstone Piledriver would help...

Wondering1 wrote: ↑

Sat Dec 03, 2022 11:31 am

robysue1 wrote: ↑

Sat Dec 03, 2022 8:04 am

Whew, back after several grueling days at hospital, worked like a rented mule!

Data is pretty much spot on in assuming that my thought is that tidal volume plays a significant role in detecting a hypopnea.

Take a look at the OSCAR chart that I posted way-back:

Since you won't take the time to draw the horizontal lines that Rubicon and I both suggested that you need to draw, I've taken the time to download your image and edit it by putting in the appropriate horizontal lines that indicate the baseline amplitude in the flow graph and the amplitude of the breaths that triggered the hypopnea being scored. I've also added vertical lines that indicate the beginning and end of the event.

Here's the edited image, slightly blown up to show both the scale in the y-direction and the hypopnea in a bit more detail:



That baseline amplitude is about 28 L/min. That's the blue dotted line at the tops of the regular sleep breathing before the big breath that ends at 5:55:40.

The amplitude of the breaths that caused the machine to flag a hypopnea shown by the red dotted line: The amplitude of those breaths in the hypopnea are at 14 L/min. Last time I checked, a decrease from 28 L/min to 14 L/min is in fact a 50% reduction in the amplitude of the flow graph---which meets (just barely) the first part of the criteria for a Resmed machine to score a hypopnea.

As for the length of the event: The start of the hypopnea is around the green vertical line at approximately 5:55:50. The end is the purple line that I've extended over the purple line with the H that Oscar drew for you. It's at 5:56:11. That means this event lasted about 21 seconds, which is more than enough to meet the part of the definition that says the reduced flow has to last at least 10 seconds.

The final criteria that a Resmed machine uses to decide when to score a hypopnea is evidence of a flow limitation. You have not included the flow limitation graph in your screenshot. But if you look very carefully at the shapes of the inhalations in the hypopnea, there is some evidence of flow limitation in 1st, 3rd, and 4th breaths of the hypopnea. It would not surprise me at all if there was a minor flow limitation visible in the flow limitation graph that lines up precisely with this hypopnea.

It's no surprise that your machine flagged this as a hypopnea: It meets all the criteria Resmed uses to decide something is worth flagging as a hypopnea.

You don't need the tidal volume graph to understand why this got flagged as an H. You do need to take the time to do what Rubicon suggested that you do on page 1 of this thread and that I suggested way back on page 2 of this thread.

There doesn't appear to be much change in the peak amplitude of the inhalations before the big breath and after, at not so as to be immediately discernable.

But there is: As I've shown with my horizontal lines, there is a reduction in flow that is right around 50% for those flagged breaths. If you changed the y-axis on the graph to go from -36 to +36, the reduction in height would be much, much clearer. The distortions in the shape of the inhalations (i.e. the flow limitations) in the flagged breaths would also become much clearer if you use -36 to +36 for the y-range of this part of the flow graph.

However, looking at the TV chart, a significant change is clear (before big breath and after).

The big bump up in the TV graph is a temporary increase caused by the large inhalation that ends at 5:55:40. That one breath does not substantially change the baseline amplitude of the normal sleep breathing before that breath occurred. But the size of that one breath does cause the bump in the much lower resolution TV graph. In other words, the "decrease" in TV that you are so attached to thinking is relevant is made much larger because TV is dropping from the amount of air you inhaled in the big breath that ends at 5:55:40 to the much smaller inhalations in the hypopnea. You should also notice that the TV graph "lags" the flow graph: In other words, there appears to be some "averaging" going on in that graph. It would not surprise me if what that graph was actually plotting was the average TV calculated over a running 2 minute window rather than the actual TV for each individual inhalation.

But more importantly, the evidence that your airway might be partially collapsed is drawn from the decrease in the amplitude in the flow graph combined with the distortions in the small inhalations that are flagged as the hypopnea.

I will add: If this were in my data, I'd be inclined to think this was a post arousal event specifically because it follows a big breath of the sort that is often, but not always, associated with an arousal. If this were my data and I was really, truly interested in trying to figure out whether this event could/should/would have been scored on a PSG, I'd be cross checking this with my FitBit data to see if there was a red dot "wake" relatively around 5:55:30-5:56:00. If there was, that would be enough to convince me this was a post arousal hypopnea that most likely would not "count" on a PSG. If not, I'd be writing this off as a possible arousal or possible marginal H or a possible "false negative" and I would not lose any additional sleep over it.

In other words, you have spent an enormous amount of time trying to use this example to prove an idea (that TV is relevant to scoring Hs) that the entire world of sleep medicine long ago decided was not relevant at all.

Frankly, I don't know if the Resmed engineers only look at the peak height of an inhalation and use that as the yardstick to evaluate subsequent breaths for possible hypopneas.

They don't. They also look at flow limitations. And to get technical, they more than likely are using something called "root square mean" analysis for analyzing a whole bunch of things connected to the idea of "peak-to-peak" differences in amplitude. But informally and for a non-math audience, all that fancy numerical stuff boils down to what's happening to the amplitudes of the peaks over time.

And they focus on the peak-to-peak differences in amplitude and a drop from the running baseline amplitude specifically because the sleep medicine community community long ago decided that a sudden decrease in the flow of air into the lungs, along with with appropriate other data channels on a PSG, indicates the airway is partially collapsed and that while the person continues to make an effort to breathe, the air flow into the lungs is compromised.

But it would appear that the TV of subsequent breaths is a clearer indication that the patient has "diminished" ventilation.

Ventilation is not what sleep disordered breathing is all about. Flow and flow limitation are the name of the game because that's what the sleep medicine community decided was important many decades ago.

Rubicon wrote: ↑

Sat Dec 03, 2022 4:32 pm

Perhaps a Tombstone Piledriver would help...

Yep. That's what I need with these critters that refuse to accept they're arguing against the entire sleep medicine community.

Either that or the explicit threat to a freshman level Calculus class: This will be on the final exam that you are taking!

robysue1 wrote: ↑

Sat Dec 03, 2022 5:15 pm

they more than likely are using something called "root square mean"

Normally when I encounter RMS, it's in the context of alternating current voltages

Keep up the good work! As painful as it must be. You might make more progress trying to teach calculus to a cat.

robysue1 wrote: ↑

Sat Dec 03, 2022 5:18 pm

Either that or the explicit threat to a freshman level Calculus class: This will be on the final exam that you are taking!

I'd be willing to bet that there's a long history of failed exams with that crowd.

robysue1 wrote: ↑

Sat Dec 03, 2022 5:15 pm

Actually here's where I have some advantage, I can numerically pick off the peaks for the two minutes prior to the "big breath" and average those.
Likewise I can pick off the peaks for the breaths after the big breath.

(My advantage is that I don't have to rely on eye-balling the data)

Here's what I found: The average PEAK for the 30 breaths prior to the big breath was 24.68.

The peaks for the breaths following the big breath were 24.90 , 21.58, 15.17, 16.38, 17.75, 19.57, 20.99

so, for each of the breaths following the big breath, the % reduction from prior peak average was:
0.89 , 12.56, 38.53, 33.63, 29.09, 20.70, 14.95

It looks like only two breaths crossed the 30% threshold. (and none were even close to the 50% you suggested)

With regard to the TV graph, the two minutes prior to the big breath the TV ranges from 462 to 495 ml.
The moment that the Hypopnea is marked, the TV is 306 ml (between 34 and 38% decrease in the TV

Wondering1 wrote: ↑

Sat Dec 03, 2022 7:20 pm

robysue1 wrote: ↑

Sat Dec 03, 2022 5:15 pm

Actually here's where I have some advantage, I can numerically pick off the peaks for the two minutes prior to the "big breath" and average those.
Likewise I can pick off the peaks for the breaths after the big breath.

(My advantage is that I don't have to rely on eye-balling the data)

Here's what I found: The average PEAK for the 30 breaths prior to the big breath was 24.68.

The peaks for the breaths following the big breath were 24.90 , 21.58, 15.17, 16.38, 17.75, 19.57, 20.99

so, for each of the breaths following the big breath, the % reduction from prior peak average was:
0.89 , 12.56, 38.53, 33.63, 29.09, 20.70, 14.95

It looks like only two breaths crossed the 30% threshold. (and none were even close to the 50% you suggested)

With regard to the TV graph, the two minutes prior to the big breath the TV ranges from 462 to 495 ml.
The moment that the Hypopnea is marked, the TV is 306 ml (between 34 and 38% decrease in the TV

Well why didn't you say so in the first place?

That would have cleared everything up 50 posts ago!

Rubicon wrote: ↑

Sun Dec 04, 2022 5:13 am

Well why didn't you say so in the first place?

That would have cleared everything up 50 posts ago!

Actually, Wondering did say that last Wednesday

dataq1 wrote: ↑

Sun Dec 04, 2022 8:42 am

Rubicon wrote: ↑

Sun Dec 04, 2022 5:13 am

Well why didn't you say so in the first place?

That would have cleared everything up 50 posts ago!

Actually, Wondering did say that last Wednesday

Well not really.

Wednesday opened the floodgate of stupid that began gushing over the dam:

Wondering1 wrote: ↑

Wed Nov 30, 2022 9:41 pm

What I noted there was that it said respiratory flow, but it did not say respiratory flow rate
That's a clue that that it's the volume of air, not the flowrate, that is determinative.

That's what leads me to speculate that it's the tidal volume graph (representing the volume) that needs to be examined

and

Wondering1 wrote: ↑

Wed Nov 30, 2022 2:19 pm

Since 330 ml is just 70% of the 470 (baseline?) it meets the criteria of hypopnea, and was so flagged.

which is irrelevant because ResMed calls hypopneas at 50%, not 30%.

So OK let's put Wonderbrain's Theory to the acid test...

Here's a pile of Tidal Volumes that drop 70%, carefully selected to allow easy maffification:



So where's the hypopnea?

Hmmm?

Rubicon wrote: ↑

Sun Dec 04, 2022 8:56 am

Wednesday opened the floodgate of stupid that began gushing over the dam:

Yeah I know the stupid would actually be gushing out the floodgate but over the dam sounded better.

robysue1 wrote: ↑

Sat Dec 03, 2022 5:15 pm

they more than likely are using something called "root square mean"

palerider wrote: ↑

Sat Dec 03, 2022 5:22 pm

Keep up the good work! As painful as it must be. You might make more progress trying to teach calculus to a cat.

Rubicon wrote: ↑

Sun Dec 04, 2022 8:58 am

Here's a pile of Tidal Volumes that drop 70%, carefully selected to allow easy maffification:



So where's the hypopnea?

Hmmm?

Is that supposed to be an example of stable breathing.?

Wondering1 wrote: ↑

Sun Dec 04, 2022 10:06 am

Is that supposed to be an example of stable breathing.?

On what planet are hypopneas part of of stable breathing?

IOWs, ya got nothin'.