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Minimum pressure question
#1
I have been paping for a year now, and found that the setting of 6 was working for me, low AHI, usually in the vicinity of less than 1 consistently. Originally on the sleep study, the tech made me sleep on my back and that caused him to say I had severe apnea, however in practice when I got home they had to constantly lower the pressure because the AHI was too high so to test my theory about sleeping on my back vs side, the lower they set it the better the AHI got. I sleep on my side, so making me sleep on my back skewed the results. The leak rates have always been very low in the range of 4.

I asked my doctor last visit about lowering the pressure to 4, he said, try it, see how you feel, so I changed it and really there has been no difference, still low AHI around the same as before.

He is going to do another sleep study (per my request) as I want to rid myself of this machine if at all possible, and since I have been so low on pressure, do I really need it? Just not sure, but after reading a few posts here, it was mentioned that you can get TOO LOW in pressure?????? Would you raise it back up?

I have found in the past few months that I am tearing the mask off around 6:00am and then sleeping until 8. I sleep better with it off for some reason now, although I think it has to do with my pillow, it skews the mask at times, although the leak rates still show they are good.

Not sure what to do until the study which will be in March. I want to take all these results to the new sleep doc.
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#2
TOO LOW would mean that either the pressure is not resolving the apnea events, or a person is having difficulty breathing comfortably.

At 4, I would be very uncomfortable thinking I could not get enough air. As a result I would end up "tearing the mask off," but I probably wouldn't be waiting until 6:00 am to do it.

But, they say everyone is different. I guess that's true. Except in my case. I'm not different, I'm the same.

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#3
wow, the important thing is getting fully effective sleep. getting the right amount, the right mix of deep and REM, etc, has a lot to do with how much you are disturbed. Check out how you score on RERAs as well. You can toggle this in sleepyhead by displaying RDI instead of AHI. If you do, you may find a difference between scores at 6 and those at 4.

Too low of pressure is not really an issue in your case because the pressures do not elevate enough for you to get used to it. The lower pressure feel different to me now that I have used 6.0 to 6.5 as a start, now under 6 seems abnormal, and 4 does seem like trying to breathe in an airplane when the ventilation isn't running (you know, like at takeoff).
Dedicated to QALity sleep.
You'll note I am listed as an Advisory Member. I am honored to be listed as such. See the fine print - Advisory Members as a group provide advice and suggestions to Apnea Board administrators and staff concerning Apnea Board operation and administrative policies. Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.
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#4
(01-14-2015, 02:28 PM)Marnid2014 Wrote: I asked my doctor last visit about lowering the pressure to 4, he said, try it, see how you feel, so I changed it and really there has been no difference, still low AHI around the same as before.

4 is extremely low pressure. Your doc will need to figure out if it's doing anything.

However I do want to mention that most masks will not have sufficient ventilation at 4, and require a minimum pressure of 5 in order to properly exhaust CO2.

Terry


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#5
I noticed that it did indeed feel harder to breathe with that pressure, interesting.

I think I will bump it back up to 5 and see where I am with that. The tearing off the mask has been happening since I had the Shingles, probably just a bad habit now. The pillow is driving me nuts as well, trying to find a "hole" to lay the hose. I tend to hug my pillows and have tried a few different ones, temperpedic, down, etc. New one again, so hopefully this one will work.
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#6
Most machines have a range of 4-20. That is by design, and for a reason, which is that the range 4-20 is the range that virtually all patients that would need an xPAP system would find efficacy. If the therapy only ever worked for OSA patients when the min pressure reached 8, for instance, they probably would have designed them to start at 8.

So while 4 is low, relatively speaking, it is in a range that effectively treats OSA for some patients. If the pressure were lower than that, it might not be helpful to anyone, which might be another reason why 4 is the lower design limit.

Will 4 work for you? Maybe. You'll have to try to find out.

So in your upcoming sleep test, were it me, I would ask them to titrate between 4-6, split the study to test without pressure, and see if there is a pressure (or lack of all pressure point) where AHI begins to rise. And again, if it were me, if the rise is significant, even at 4, or at no pressure, I would keep wearing the mask, every day for the rest of my now-lengthened-by-xPAP-therapy life.

I would also get verification on that C02 exhaust statistic. Not that I doubt it, I just think it needs confirmation. It may also explain why even though the machine is capable of 4-20, that my sleep doc, and from what I can tell, others, set the starting "wide-open" therapy at 5-20.

Thanks, Terry, for that little nugget. It is interesting. It may be that the legacy design of xPAP no longer fits what masks are doing (it sounds like the exhaust stat issue might be something that applies to newer masks). Something to keep an eye on.
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#7
(01-14-2015, 03:47 PM)TyroneShoes Wrote: Most machines have a range of 4-20. That is by design, and for a reason, which is that the range Thanks, Terry, for that little nugget. It is interesting. It may be that the legacy design of xPAP no longer fits what masks are doing (it sounds like the exhaust stat issue might be something that applies to newer masks). Something to keep an eye on.

They all seem to have a minimum pressure rating of either 4 or 5.

It's not a huge deal, but something to consider, since it effects the CO2/O2 levels.
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#8
Sorry to say this, but I spent much of my life re-breathing my air. Like another here on the forum, up until last year I slept with my bed sheet over my head. I survived, perhaps miraculously. Anyway that don't make it right.
Dedicated to QALity sleep.
You'll note I am listed as an Advisory Member. I am honored to be listed as such. See the fine print - Advisory Members as a group provide advice and suggestions to Apnea Board administrators and staff concerning Apnea Board operation and administrative policies. Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.
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#9
(01-14-2015, 03:25 PM)Terry Wrote: However I do want to mention that most masks will not have sufficient ventilation at 4, and require a minimum pressure of 5 in order to properly exhaust CO2.

Terry

I think most masks will adequately remove CO2 in terms of safety at a pressure of 4 cmH2O. However, some people will find the air feels stale at 4 and may feel like they can't breathe or will have claustrophobic feelings.
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#10
(01-15-2015, 04:23 AM)archangle Wrote: I think most masks will adequately remove CO2 in terms of safety at a pressure of 4 cmH2O. However, some people will find the air feels stale at 4 and may feel like they can't breathe or will have claustrophobic feelings.

Just going by the data in the mask documentation. 8-)



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