general question about flow limitations

I have been watching youtube videos about OSCAR, trying to figure out how it works. I came across 2 videos on flow limitations. They seem to contradict each other or maybe I just don't understand what they are saying. (I suspect the latter.) Could someone explain this to me? Thanks.

CPAP Friend
https://www.youtube.com/watch?v=LwOjeESNGIY

LankyLefty
https://www.youtube.com/watch?v=7W_9u1hEum4

Flow limitations, or UARS, are partial blockages in your upper airway that are too low to be considered a hypopnea but can still affect the quality of your sleep.

Something most experts agree need to be watched and accounted for when optimizing therapy. The best way seems to be by increasing the difference between inhalation pressure and exhalation pressure by using PS (AirCurve)., EPR (AirSense) or softPAP (Lowenstein).

If I recall correctly, LeftyLanky at one point said Flow Limits didn't matter. That is when I stopped watching his videos because they clearly do matter.

OSCAR shows flow limits for ResMed devices. I believe, from my earlier research, that your 95% value for FL should be 0 or very very close to it. And the 99% be less than 0.15. If higher then you would benefit from a greater pressure supprt / EPR.

ResMed AirSense devices max out at EPR of 3. If you need a greater pressure support, then you would need a Bi-Level like the AirCurve 10.

Note: on ResMed, if you increase your EPR, you need to raise your pressure by the same amount. i.e. if you are at IPAP of 10cm and change your EPR from 0 to 1, then you would need to increase your IPAP to 11cm. Each EPR level, lowers your EPAP and that is where obstructive apneas occur, at the end of the exhalation cycle. If you go from EPR of 1 to 3, then you would need to add 2 cm to your IPAP pressure and so on.

Phillips and Lowenstein do not need to have their pressure increased when using pressure relief as they use a different algorithm

Hope this helps.

And here is a good write-up about Flow Limitations:

https://www.apneaboard.com/wiki/index.p ... limitation

SakimaStorm wrote: ↑

Tue May 07, 2024 12:45 pm

If I recall correctly, LeftyLanky at one point said Flow Limits didn't matter. That is when I stopped watching his videos because they clearly do matter.

Oh really?

In what way?

SakimaStorm wrote: ↑

Tue May 07, 2024 12:45 pm

If I recall correctly, LeftyLanky at one point said Flow Limits didn't matter. That is when I stopped watching his videos because they clearly do matter.

In the LL video, I think that is what he is saying. He looks at something else? I didn't quite get it, but then all these graphs just make me confused.

CPAP Friend is saying the opposite. I think. He cites some research.

Possibly flow limitations matter to some people but not to everyone. Wish I could figure that one out because I seem to have them and have not had good numbers recently.

I like LL because he is funny and seems knowledgeable, but the cost of his consultation....$400??!! Oh. My. God. If these things (flow limitations, for example) are open to disagreement, and he is sure he is right, which it seems he is very sure of himself, then that's not how I would spend $400, if I had it, which I don't, so no skin off his nose.

If you can, post an OSCAR screen capture showing your breaths in about 3 second spacing (go under events and select 3). And also your summary on the left side showing your FL numbers.

Posting images here is problematic due to space so if you can post them elsewhere and link that would be great. Or else attach them in a PM to me and I'd be happy to take a look.

Also you can compare your inhalation waveform to those on this page:
https://www.apneaboard.com/wiki/index.p ... limitation

And if you see the top of your inhalation wave is flattened, that's a good indication you are having disrupted sleep due to FL, and of course possibly other things.

I'm certainly no expert, but I may be able to spot some things that might be worth trying and/or looking into.

What are your settings on your Autoset? Using EPR?

SakimaStorm wrote: ↑

Tue May 07, 2024 4:51 pm

If you can, post an OSCAR screen capture showing your breaths in about 3 second spacing (go under events and select 3). And also your summary on the left side showing your FL numbers.

Posting images here is problematic due to space so if you can post them elsewhere and link that would be great. Or else attach them in a PM to me and I'd be happy to take a look.

Sorry, I'm not sure what you mean. I clicked on events, but I'm not sure what I'm supposed to do next. Do you mean move the size bar on the bottom?

Oh, no worries.

Yes, move the slider on the bottom to the right and then left until it shows 3 and then your flow waveform should show nicely. Use your left and right arrows (on your keyboard) to scroll left and right till you find a typical area and take a look at the top of the inhalation curve. Should be pretty round. If flat or downward sloping, then there are some flow limitations. Obstructions will likely be flat and then jagged and irregular, but to look for FL, check regular waves that aren't showing obstructive or hypopnea events.

https://i.postimg.cc/bY0Hrgsv/FlowRate.png

You can also select Flow Limits to be charted and displayed on the right (by picking Flow Limits from the event types pick list on the bottom left) and then look and what you see. Hopefully it is mostly at 0 with a few spikes that are less than 0.5

https://i.postimg.cc/Pxd2xDX9/Flow-Limits.png

And here is the entry on the left side of the Oscar display. You should see numbers like this:
Channel Min Med 95% 99.5%
Flow Limit. 0.00 0.00 0.00 0.09

Deleted.

Great. Yes, that is what I wanted to see.

Your waveform looks good. No flow limit problem that I can see. You are running on CPAP mode (fixed) with EPR of 3 so it won't report flow limit values, that is only done when running in APAP mode. But the shape of the waveform looks good.

Your obstructions are well handled as are your hypopneas. Your Centrals are bad though, and that might be why you aren't sleeping great.

Sometimes centrals are high when you first start therapy and then go away. They can also occur when the pressure is too high.

Did your doctor put you on 10cm fixed w/ EPR 3?

To see if Centrals can be reduced by pressure, you can try changing to APAP mode, keep EPR on 3, and set min pressure on 6 and max on 10. And then see if you sleep better. And repost so we can see if there is any change on Centrals.

If the reduction of Centrals doesn't happen with the APAP mode and less air, then you will probably want to take the data to your doctor and see about getting a Bi-Level machine, like the AirCurve 10, that is made to handle central apneas. That is beyond my experience and ability but finding out if this is caused by too much air can be done by going to APAP mode with a 6 to 10 range.

ps -
If you try this and find it is too hard to breathe initially, set min pressure to 7 instead of 6. A lot of people need a min of 7 to be comfortable but some are fine w/ 6.

In case you don't know, central apneas (clear airway apneas) occur when the airway is open but the brain doesn't detect a need to breathe (usually due to high oxygen levels in the blood) so it doesn't tell the body it is time to take a breath until the CO2 levels rise enough to trigger a breath. Sometimes caused by too high of air pressure, sometimes by a medical condition (which would require a special bi-level machine to handle.)

Did you sleep study mention centrals? If not, then this may all be pressure related.

Also, make sure your hose type and mask type are set correctly in the settings.

onward60 wrote: ↑

Tue May 07, 2024 8:47 pm

Is this even remotely what you're talking about? I'm not even sure how I got this. I was hoping for something that included a central, but this popped up from who-knows-where.

You got this by trying to scroll up and down with the arrow buttons. On OSCAR, they create zoom in (up) and zoom out (down). Confusing as hell...
You have to use page up and page down, or your mouse, to scroll on the screen.

To get that period of CA's, use your mouse to place the cursor in the center of that time period on the top chart, and use the arrow keys to focus on that time period. The period you focus on has a white background on the top chart. All the rest has a green background.

Please post your CA image on your other thread.

I'll try.

EDIT: Leaving this thread. I do not like arguments with snarky comments.

I was just hoping for a general answer to the significance of flow limitations, but there doesn't seem to be a simple answer. Going back to my thread about soft response.