Question about Flow Limitations

[BetsyV]

I've been on CPAP for nearly 10 years, with the pressure at 5. For the past month I've been testing out a Resmed Airsense 10 Autoset for Her, set to min 5 and max 12. Still using the same Swift LT nasal pillows as always.

It's taken a while for me to get used to the higher pressure -- for the first couple of weeks I was waking up several times a night because of it. I don't feel like my sleep is better or worse than on my original CPAP, although I did try one night with the machine set to CPAP mode at 5 and my AHI was definitely higher -- just over 3 rather than hovering around 1.

I'm curious about the Flow Limitations graph, though. It looks unusual to me. My understanding is that flow limitations are part of what bumps the pressure up, but if I zoom in it actually seems as if the increased pressure may also be triggering FLs? I don't know what to make of the data.

(In case you are wondering, I have not had a sleep study in 8 years or so. I'm trying to avoid it because I have a severe adhesive sensitivity/allergy. But it may yet come to that.)

Thanks!

Aug8_2018.jpg (551.95 KiB) Viewed 1112 times

[Fetou]

Keep in mind that snores also increase pressure, so you may want to look at that graph as well.

For me, more pressure got rid of my flow limitations. Still collecting data, but arousals look less frequent and sleep less fragmented.

[BetsyV]

Thanks! I checked snoring and it's minimal.

[Pugsy]

Are you having any nasal congestion issues at all?

If not....would you do me a favor and switch to the non for her autoset mode and leave all the settings the same otherwise?
The for Her mode makes the FLs look worse (at least from my experience) and I would like to see just how much difference there is between the 2 modes in both what the FL graph looks like and the pressure response line.

[BetsyV]

I do have life-long allergy and sinus problems, but I feel it's pretty much under control through routine use of allergy pills, nasal rinse and decongestant. This also isn't a high-allergy time of year for me. If allergies were the issue I'd think it would get worse over the course of the night as the effect of the rinse and the meds wear off... but that doesn't seem to be the case.

I'll try switching the settings for tonight. I'm back to the clinic tomorrow and may be returning this machine -- it's a loaner and I'm not sure how long I keep it -- but I will download the data. And I may end up buying an identical one.

Thanks!

[Pugsy]

Thank you for being my guinea pig. I have tried both modes myself but my FLs are pretty much non existent and I am not a good guinea pig. I could see some evidence of the for Her mode making mountains out of my mole hills but since I don't have much in FLs anyway it's not a good comparison. Yours is perfect because they FLs are so pronounced.

[BetsyV]

Here is last night's chart. Still a fair bit of FL but not nearly as much once the setting was changed. So how does the Autoset for Her differ, in order to do this?

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[Pugsy]

I don't know why the obvious difference. I never could find any documentation that explained it.
Supposedly the for Her mode target FLs more but I don't see how that would cause the sensors to change the reporting of what they see. I also don't know just how critical that difference is in the grand scheme of things.

You can see how the pressure graph roams around a lot more in the regular mode than in the for Her mode. The pressure changes are indeed more subtle which is what they say they will do but they never really tell us why the difference in the reporting scale of the FLs.

They say that the pressure response is more gentle and it's obvious that is the case but why they need to report such a big difference in the graph results itself is a mystery to me.

The more subtle pressure changes is for in case someone is disturbed by the rather marked changing of the regular mode.

I see several wake ups where you turned the machine off...any reason why?

Can you tell any difference in how you feel this morning compared to yesterday?

[Arlene1963]

I always enjoy learning from threads about flow limitations.

Just a quick question/observation:

In the first chart the respiratory rate is very high compared with the second chart.

Any idea why this might be the case and would this be connected to the FLs reported?

[Stom]

I don't know why the obvious difference. I never could find any documentation that explained it.

In comparison, ResMed AutoSet for Her evaluates the flow for every breath looking for apneas, snore, and flow limitation, and delivers a proportional increase in pressure depending on the degree of deviation of the event from normal, modulated by the current pressure setting and leak rates. If pressure is >10, then the response to flow limitation reduces and a louder snore is required to produce a response.8 Both AutoSet for Her and AutoSet respond less as leak gets higher.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4629962/

I still don't really understand the different algorithm, but the paper above goes into the different responses to events used by the regular A10 and the FH A10, and also has citations to the patents, which you can look up on Google patents.

[Pugsy]

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4629962/

I still don't really understand the different algorithm, but the paper above goes into the different responses to events used by the regular A10 and the FH A10, and also has citations to the patents, which you can look up on Google patents.

Thanks.

I don't have time right now to be doing any research into this. Maybe later. I have too much other stuff going on right now.

[Jay Aitchsee]

It is possible that SleepyHead may interpret FL from the FH algorithm differently than from the non-FH. Or, put another way, the machine might report FL differently in the FH mode. It could be just a matter of scale. Also, as to Arlene's point, we know that SleepyHead sometimes gets the RR wrong. To see, we would have to zoom in and count the breaths to verify.

It would be interesting (to me) to run the comparison using ResScan.


Bottom line, I think, is whichever is more comfortable to the user.

[Stom]

It is possible that SleepyHead may interpret FL from the FH algorithm differently than from the non-FH. Or, put another way, the machine might report FL differently in the FH mode. It could be just a matter of scale.

Possible, but I think what is going on is that FH **scores** flow limitations differently and sleepyhead is accurately showing the machine scoring. The FH scoring may be different for the exact same flow limitations than the standard Autoset algorithm. Check the paper I cited earlier for details on the different score weightings between the two,

[Jay Aitchsee]

The FH scoring may be different for the exact same flow limitations than the standard Autoset algorithm.

I think that is what I was trying to say

[BetsyV]

I see several wake ups where you turned the machine off...any reason why?

Can you tell any difference in how you feel this morning compared to yesterday?

The higher pressure wakes me, with aerophagia or dry mouth or sometimes just because I perceive that I'm fighting to breathe. So I whack the machine, belch, take a drink of water, and let it ramp up again. Twice in one night is not so bad. I often have four or five awakenings with this machine, which didn't happen with the old CPAP.

And I feel pretty tired today compared to the past few weeks. I don't know why. I have the machine for another couple of weeks so I'll see if it persists.