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Can increasing pressure *increase* AHI?
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GuitarManDave Offline

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Post: #1
Can increasing pressure *increase* AHI?
I recently started on CPAP. I had used a custom-made dental appliance for 10 years until recently when my wife noticed that I was having a lot more apneas. I've had 4 sleep studies over the years and there have been hints that I have complex apnea because I definitely have some central events. This is consistent with the way my wife describes my sleep - that often I'm not struggling to breathe, rather that I'm holding my breath intentionally.

When I started on CPAP 4 weeks ago, sleepyhead showed me having a lot of centrals. I asked my doctor about it she said I should turn off the EPR since that can actually induce central apneas. It seemed to work - after turning it off my AHI went down and my incidence of central apneas dropped appreciably. Sleepyhead does reveal many periods of periodic breathing but with the EPR off it does not devolve into a central apnea.

So once I got the centrals worked out my AHI leveled off around 3.4. I feel this number is misleading, however, since I sleep perfectly soundly with no events and no snoring until about 3am when my hourly AHI spikes up to 10 or higher. Almost all of the events are obstructive apneas with very few hypopneas and little snoring. My APAP cranks the pressure up to the maximum setting prescribed by my doctor: 9 (the low is 5).

In an attempt to reduce my AHI even further I've been gradually increasing my pressure from 9 to 9.6 then 10 and strangely enough my AHI has actually increased to a 3 day average of 5.8 which I don't understand at all. Still no hypopneas, no snoring, but lots of obstructive apneas.

I don't understand this at all. Is this just a coincidence or could increasing the pressure actually increase my AHI? I guess I'll try lowering the pressure and see what happens. I'd appreciate any thoughts as to what might be going on.

Thanks,
Dave
04-22-2013 08:22 AM
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Bompa Offline

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Post: #2
RE: Can increasing pressure *increase* AHI?
I'm not so sure that turning off EPR would solve your problem. Personally I can't get by without it set at 3.

As for your AHI numbers, anything under a 5 is considered good. Not too many users get a 0 reading night after night.

Hang in there, more members will be along to advise.
Coffee
04-22-2013 09:53 AM
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Shastzi Offline

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Post: #3
RE: Can increasing pressure *increase* AHI?
What may be happening is you might be rolling on to your back and that is causing more problems than your current pressure can handle. (on your back you get a lot more gravity problems and tissue collapses more easily)
Since you mention that around 3am (The witching hour!) all kinds of OA's are showing up.
I had the same thing happen to me.
I found that wearing a small backpack loaded with 3 tubes of tennisballs works like a charm.
Try that trick first for a week and see it helps.
Before that I was getting occasional peaks of 10-12.8 AHI (not good!)
Now I am staying below 4.5.

Keep checking with your MD often.

While you're at it study the *duration* of these events from your flow rate graphs.
if they are less than 25 seconds and spaced far enough apart 10-15 min or more, you should be ok

Good Luck!

"With ordinary talent and extraordinary perseverance, all things are attainable." - Thomas Foxwell Buxton

Cool
04-22-2013 07:16 PM
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Sleepster Offline
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Post: #4
RE: Can increasing pressure *increase* AHI?
(04-22-2013 08:22 AM)GuitarManDave Wrote:  When I started on CPAP 4 weeks ago, sleepyhead showed me having a lot of centrals. I asked my doctor about it she said I should turn off the EPR since that can actually induce central apneas.

Interesting. This is an effect that's been discussed here and I'm glad to have it confirmed. When I switched to a BiPAP my central apnea index (CA) went up, and that is essentially the same effect as a BiPAP lowers the pressure even more than EPR on exhale.

Quote:In an attempt to reduce my AHI even further I've been gradually increasing my pressure from 9 to 9.6 then 10 and strangely enough my AHI has actually increased to a 3 day average of 5.8 which I don't understand at all. Still no hypopneas, no snoring, but lots of obstructive apneas.

So it's your OA (obstructive apnea) index that's gone up, not your OA index? Raising the pressure can make your OA index rise.

It's probably just a coincidence. See if your pressure has maxed out when you're having those series of OA's.

Sleepster
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04-22-2013 07:42 PM
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zonk Offline

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Post: #5
RE: Can increasing pressure *increase* AHI?
(04-22-2013 08:22 AM)GuitarManDave Wrote:  My APAP cranks the pressure up to the maximum setting prescribed by my doctor: 9 (the low is 5).
As you,re experimenting with pressure range, I would increase both minimum and maximum pressure
I do very well with APAP but some people do better with CPAP as they find pressure changes disturbing
Keep in mind the machine would not go any higher than needed even if maximum pressure set at 15 or higher
The minimum pressure is most important, has to prevent airways from collapsing and the maximum pressure to deal with more stubborn apnea as in clusters, sleeping on your back or REM sleep which could explain the early morning events

S9 Autoset detect central sleep apnea but does not treat central sleep apnea or complex apnea
04-22-2013 08:00 PM
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archangle Offline
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Post: #6
RE: Can increasing pressure *increase* AHI?
The body is a complicated and strange machine. Sometimes it works the opposite of what you expect. Keep tinkering carefully.

How long are your apneas? Short ones are less worrysome.

It's also possible you ARE having centrals, but they show up as obstructive.

Get the free SleepyHead software here.
Useful links.
Click here for information on the main alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check it yourself.
04-22-2013 11:33 PM
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