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Confusing results
#1
S9 Autoset. After losing a LOT of weight I am trying to see where I am, short of another sleep study. In the beginning my set point was 12.5. When I got the s9 autoset I set it t0 8.5-13 and usually got AHI <5 and the pressure mean and 95th% was near the top.

Now, in my experiment over many months after weight loss, I have slowlylowered the range from 8.5-13 to 4-6! My AHI is usually <2.5 but the median and 95Th% still end up near the top of the range I set.

I don't understand this. I know the S9 algorithm responds to flow limitation events, not apneas, but it sure seems that is it too aggressive for me. Too bad you can't slow it down or desensitize it.

I think my next step will be just to run it in CPAP mode @6. I have read that is the lowest safe number to clear CO2. If that still yields very low AHI, off it comes.

Please comment on this, am I missing something
?

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#2
We've had several others with weight loss experience slow decline in AHI. Or no decline at all.

And keep in mind that skinny people have sleep apnea too. Just because you have lost weight does not mean you are "cured". You cannot know that for certain without a sleep study. While the Autoset is good, it is not a sleep study.

If you are sleeping on your back or are on certain medications, those could be to blame for the still necessary higher treatment pressure.

Are you viewing the data?
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#3
(08-13-2014, 12:17 AM)zbaba4 Wrote: Please comment on this, am I missing something
?
I cannot comment on your experiment but you might want consider an oximeter to monitor your oxygen levels while you sleep
Drop of O2 levels below normal range can be bad to your health regardless of AHI

Some people are on low pressure but anything lower than 9 would feel like like suffocating to me and not getting enough air to breathe

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#4
(08-13-2014, 12:17 AM)zbaba4 Wrote: I have read that is the lowest safe number to clear CO2.

Could someone explain this to me- "clearing CO2"
2010 sleep study 63 AHI, 2014 3.0
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#5
(08-13-2014, 12:17 AM)zbaba4 Wrote: S9 Autoset. After losing a LOT of weight I am trying to see where I am, short of another sleep study. In the beginning my set point was 12.5. When I got the s9 autoset I set it t0 8.5-13 and usually got AHI <5 and the pressure mean and 95th% was near the top.

Now, in my experiment over many months after weight loss, I have slowlylowered the range from 8.5-13 to 4-6! My AHI is usually <2.5 but the median and 95Th% still end up near the top of the range I set.

I don't understand this. I know the S9 algorithm responds to flow limitation events, not apneas, but it sure seems that is it too aggressive for me. Too bad you can't slow it down or desensitize it.

I think my next step will be just to run it in CPAP mode @6. I have read that is the lowest safe number to clear CO2. If that still yields very low AHI, off it comes.

Please comment on this, am I missing something
?

Why are you trying to lower the pressure so much? It sounds to me like you needed to leave it at 8.5/13 and watch where it actually sits. Then move it up or down a tiny bit at a time until you reach a point where the ahi gets as good as it can get.

Granted everyone's different, but a 4/6 setting for me would be awful. But then, I'm not different, I'm the same.

At 8.5/13 you might try setting the EPR to 2, which will allow a little lower exhale. That might feel better to you.

Anyhow, maybe it's me that's missing something?

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#6
I understand his point and I think it has some merit. If things have changed enough that a new sleep study would say you no longer needed CPAP, how would you even know without having another sleep study??? I think the answer may be as he suggests, run the CPAP box at its lowest safe setting and see what gets flagged. If you see no alerts or precious little flow restrictions, I'd say put the machine in the closet until you gain all that weight back and need it again. You could run a session occasionally just to be sure you were still out of the woods.

capiche?
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#7
(08-13-2014, 06:43 AM)readyforsleep Wrote:
(08-13-2014, 12:17 AM)zbaba4 Wrote: I have read that is the lowest safe number to clear CO2.

Could someone explain this to me- "clearing CO2"

The mask needs a certain minimum volume of air flow to expel the CO2 being breathed into it by the patient. At some point of lowering the pressure the volume of flow is reduced to the point that you are in danger of re-breathing your own waste product. I don't know what point that occurs at but 6 cm WC sounds reasonable.

edit. That obviously doesn't apply to nasal masks.

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#8
zbaba4, My results are often confusing too so you're not being singled out. I often get full 45 second apnea incident flagged while I'm still awake not to mention several centrals. This makes me distrust this device even more than I naturally do. I have decided to ignore all incidents for the first 1/2 hour +- of any nightly session and make my own computations based on the remainder of the night. That may not be so accurate either since I wake up a couple of times every night and lie there for maybe 1/2 hour before getting back to snoozing. If I knew exactly when those times were I could discount anything from that time frame also. I could keep a log but somehow that would defeat the purpose and keep me awake even longer. We sorely need that cheap easy way to determine/record when we are awake that is being discussed in that other thread.

Perhaps someday these devices will get smart enough to ignore what happens when we're awake. Even better would be they get smart enough to be certified for a sleep study so we don't have to pay the MM for that. Don't hold your breath ( bad choice of terms, what? ) on that one though.
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#9
Thanks for all replies. WHat bothers me is that in autoset mode my pressure always rides near the top but my AHI remains very low, like no difference between 12 and 8. Would seem to indicate CPAP not needed.

AHI as diplayed on the user screen is useless. I look at actual data, subtract events while I am awake ( I take off mask if I wake up). When I put it back on I get a flurry of events while awake. The whole CPAP thing is not useful if you are sure you are awake.

Anyway, I will creep down to 6 in CPAP mode. BTW, anyone one have sleep study results with CPAP settings between 4 an 6?
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#10
(08-13-2014, 06:43 AM)readyforsleep Wrote:
(08-13-2014, 12:17 AM)zbaba4 Wrote: I have read that is the lowest safe number to clear CO2.

Could someone explain this to me- "clearing CO2"
From: http://www.resmed.com/au/assets/document...ac_eng.pdf

WARNING
• The vent holes must be kept clear.
•This mask should only be used with CPAP or bilevel devices recommended by a physician or respiratory therapist.
•The mask should not be used unless the device is turned on. Once the mask is fitted, ensure the device is blowing air.

Explanation:
CPAP and bilevel devices are intended to be used with special masks (or connectors) which have vent holes to allow continuous flow of air out of the mask. When the device is turned on and functioning properly, new air from the device flushes the exhaled air out through the mask vent holes. However, when the device is not operating, insufficient fresh air will be provided through the mask, and the exhaled air may be rebreathed. Rebreathing of exhaled air for longer than several minutes can, in some circumstances, lead to suffocation. This applies to most models of CPAP or bilevel devices

As with all masks, some rebreathing may occur at low CPAP pressures.
• Refer to your CPAP or bilevel device manual for details on settings and operational information.


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