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Leaks vs effective AHI control
#1
Greetings, all. After getting everything working well with the S9AutoSet and most all mask problems under control, I found myself no longer downloading data from the SD card to look at details on the computer. Instead, each morning I have been checking the data available on the Autoset's screen to see how it went during the night. Over time, this has raised a question in my mind about just how much or how little short periods of excessive mask leaks affects overall treatment.
On a recent morning, the screen showed a leak rate of 30 and a nice low AHI under 2 which is excellent for me. I recalled having a good no-leak sleep for most of that night. So, I took a look at the detailed data, and this confirmed my impression. There were only about 7 or 8 minutes of a 30 leak at the start of that night. The remaining hours showed nice low leak rates with some periods of leakage near but not over the magic red line.
I understand that too high a leakage can affect other data, but how much for how long corrupts other data and specifically AHI? I ask this question knowing that there may not be a specific answer.

Here's a second possibly related question. Every now and then, after getting out of bed for a potty break, I've had what seems like a higher than normal amount of pressure coming into the mask when I restart the S9. When this occurs, I reach down and stop the machine for a moment and then restart it. Usually, on its second start up, the pressure feels lower and more in line with where it was when I turned it off to get up. Has anyone else had a similar experience? It has me wondering if it's just my impression and not a real change in delivered pressure, or is there something going on with the machine?
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#2
Regarding your first question a high leak period can affect results during that period. In other words, for those 7 or 8 minutes it is possible that you could have something going on and the machine not deal with it appropriately. Not likely, but possible. Also, 30, although higher than Resmed wants to see, isn't really all that bad. So there's that. And finally 8 minutes of your overall night isn't anything significant at all.

Now, about your pressure settings: You indicate your pressure is set to a minimum 10 and a maximum 20. What is your average pressure and your "always below 95%" pressures? Let's say just for the sake of argument that number is 12. At 12, a minimum of 10 would be fine, but the maximum of 20 is too high. If you dropped the maximum from 20 down to perhaps 15? I think the second question you ask may resolve, and I wouldn't be too shocked if the ahi didn't fall a little.

But it all depends on what your actual numbers are. So come back with that and we'll speculate further.
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#3
(10-15-2014, 07:28 PM)Dawei Wrote: I understand that too high a leakage can affect other data, but how much for how long corrupts other data and specifically AHI?

If the reading from the flow rate sensor indicates too high of a leak rate, then it's no longer capable of accurately detecting apneas and hypopneas, which means it can't accurately measure the AHI.

Quote:It has me wondering if it's just my impression and not a real change in delivered pressure, or is there something going on with the machine?

Read the pressure from the on-screen display. It should start at the minimum.
Sleepster
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#4
retired_guy pretty much covered it (but you can't just post "+1" on this forum -- it's too short a message.)

Leaks above 24 (for Resmed) don't deliver effective treatment -- occasional leaks aren't that big a deal from THAT point of view.

However, any leak can be a nuisance if it wakes you or otherwise disturbs your sleep -- after all the point is to get restful continuous sleep, not waking up to the sound or annoying feeling of a leak in your eye or some such.

Sweet Dreams,

HerbM
Sleep study AHI: 49 RDI: 60 -- APAP 10-11 w/AHI: 1.5 avg for 7-days (up due likely to hip replacement recovery)

"We can all breathe together or we will all suffocate alone."
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#5
Hi Dawei,
It's good to hear from you again, it's been a while.
Hang in there for more answers to your question.
trish6hundred
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#6
Many thanks for some really good answers! Retired_guy, it looks like the only pressure range tweaking that might help is to bring up the lower number, since max. pressure is up at 19.9 (for the past 3 months and earlier than this period too), believe it or not. Reminds me of a comment from my sleep doc early on to the effect that my apnea isn't going to be easy to get under control. The 95th percentile pressure has been 18.5 for the past three months and 19.0 for just the past month. The median (have to look that up to recall if it's the same as average) pressure was 14.6 for the past 3 months. So, that would seem to suggest bringing the low end up from 10 to about 14?
Thanks for helping put the higher than desired leak rate business into perspective, herb and retired guy.
And Sleepster, your suggestion is something that hadn't crossed my mind. Thanks. It's all too obvious, isn't it.
Yes, it's been awhile, Trish. Nice to see you're hanging in there with greetings to everyone new to the forum.
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#7
Yes, I would move the low end up a bit. Maybe to 12 or 13 since your average is just over 14. With that high of a low end, you may need to turn the ramp on if it is uncomfortable for you to go to sleep.

I am wondering about your full mask however. You are doing fine with it as far as controlling leaks are concerned, but I wonder if using a nasal mask or even a pillows mask might allow you to use a lower pressure? Not easy thing to find out though, so it's just something to think about.
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#8
(10-16-2014, 04:00 PM)retired_guy Wrote: I am wondering about your full mask however. You are doing fine with it as far as controlling leaks are concerned, but I wonder if using a nasal mask or even a pillows mask might allow you to use a lower pressure? Not easy thing to find out though, so it's just something to think about.

R_G,

Why do you think that?

Best Regards,

PaytonA
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#9
No super strong reason Payton. It just intuitively seems to me that a Full Mask, more so than a FFM, or a Nasal mask might require higher pressures to accomplish the same desired effects.

It just seems like anytime I see someone that is using a full mask their required pressures are very high.
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#10
I can sort of vouch for the pressure running a bit higher over all with a Fitlife total face vs a nasal mask.

I started with the Fitlife and it works extremely well. I was gifted a nasal mask though its a small and I think I would probably take a size larger really but I tried it off and on to see if I could use a nasal mask.


Invariably I get a bit lower AHI with nasal, and lower max and mean avg pressures with my auto than I do with the total face.

Not huge differences but enough and regularly enough to show a lean to the nasal for a bit better AHI and a bit lower pressures.

Just an aside. I had no aerophagia problems with the Fitlife while with the nasal I will occasionally give off a couple of burps when I get up. Very little and not a problem but with nasal I do have it and with Total face I dont.
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