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Benefits of Fixed Pressure??
Benefits of Fixed Pressure??
My sleep doc is calling me a "variable pressure failure" and scheduled a sleep titration study for fixed pressure. 

What are the benefits of fixed pressure?

I've read some of the wikis and see lots of variable pressure benefits. Found one old post where clownbell reports being helped by fixed pressure but that seems very uncommon. 

What would suggest the need for fixed pressure?
What suggests "variable pressure failure"?

The only data my sleep doc reviewed was my AHI. 
90 days = 1.87
30 days = 2.01

Current AS11 with min 7cmw, max 9.8, EPR 3

Sleep doc was very unhappy I had adjusted my pressures and had numerous inaccurate statements in her notes.
It feels like they just want to bill the insurance for another sleep study and don't give a hoot about helping me feel better.

I'm 183 nights in and still not feeling any benefits from the cpap.
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RE: Benefits of Fixed Pressure??
Hi, Brazen  I consulted a registered polysomnographic technician (sleep tech) who recommended changing to a fixed pressure.  The rationale was that pressure changes can disturb one's sleep.  

One of his concerns was that I hadn't been having much REM sleep.  This showed up in my initial in-lab sleep study, and, during the online consultations, he also assessed that based on the shape of my breathing pattern shown in OSCAR.
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RE: Benefits of Fixed Pressure??

I don't know the benefits Fixed Pressure.

I don't know about a sleep titration what I would want and I don't even know if they do this; since you think you have different sleep issues, what if a polysomnography done while you are on a xPAP controlling events maybe more will be discovered of your sleep cycles.

I must of lost tract of your posts. I remember you were at a low pressure and with EPR of 3 EPAP was 4. Those scans seemed pretty level.

I know you had bloating and did not want to increase pressure much. Your max pressure was under 10ish. Did you ever set min pressure to 9 or so so EPAP stayed above 6. See how that went.

I would not say you were a "variable pressure failure". If I remember correctly, you had a lot of bloating so pressure stayed low.

What about a AirCurve 10 VPAP, the PS/EPR can go higher than 3 hopefully help with flow limitations.
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RE: Benefits of Fixed Pressure??
Lucid - thanks for that info
I don't really feel like my sleep is disturbed but my Fitbit suggests really low REM so maybe it could be helpful to go to fixed pressure. (Fitbit accuracy is questionable)
My REM was almost nonexistent during my sleep study but they blamed that on sleep apnea. (No cpap/titration during that study)

I've misplaced my laptop in a recent move (it's packed here somewhere! Lol) so I can't share any OSCAR data on my regular therapy thread so thought starting a new one just for questions about fixed pressure might be alright. 

I agree about the benefit of a full sleep study while on a Xpap. It's the only reason I agreed to this study she wants - they tell me it's a regular polysomnography with cpap titration to fixed pressure being the order from the doc.

I was experiencing terrible aerophagia at higher pressure. Before my move, my OSCAR reports looked about as good as I think I can get.
Flow limit stays right around 0.00-0.03.

I'm supposed to meet with a different sleep doc (because the current one fired me right after ordering the titration study) three months after my titration. I can only hope she's better.
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RE: Benefits of Fixed Pressure??
I for one, don't respond favorably to a variable pressure, normally. I've found that pressure changes will cause arousals if the change is greater than 1 cm. It will not show up in my sleep data, but the next day I'm tired and feel out of sync with the world. Now that I have said that, I'm currently using a variable pressure, but have found my sweet spot. The pressure only changes .6 cm between the minimum and maximum.

- Red
Crimson Nape
Apnea Board Moderator
Useful Links -or- When All Else Fails:
The Guide to Understanding OSCAR
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RE: Benefits of Fixed Pressure??
Red - thanks
It's helpful to hear there are sometimes reasons and value in a switch to fixed pressure. 

I hadn't considered that variable pressure could be disturbing my sleep. It's not causing conscious arousals but could be disruptive anyway.
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RE: Benefits of Fixed Pressure??
Except for when I'm really tired, and except for the last 20 minutes of a decent night's sleep (for me anything over six hours), I only dream seldom during the early hours of sleep.  I may be two or three REM cycles in the first five hours, but I'll get two or three in the last 45 minutes.  Dunno why, but my RT said those last dreams are a sign of good quality sleep, and if you get them, you should be grateful.

However, it doesn't follow that those few earlier hours of cycle and REM are not that important.  For one thing, at least if my Galaxy watch has it right, I get most of my 'deep sleep' within the first three hours.   I almost never show deep sleep in the last two hours.  But I get lots more REM, as I said.

All this to say that the cycling is quite, even exceedingly, important.  If you get disturbed in any way, aroused from mask and pressure interferences, or from flow problems, you aren't going to get the same quailty of sleep.  And that's not good...at all.  So, if what you're using, and the way you use it, are robbing you of quality rest, it should be no wonder that you aren't feeling particularly keen or well-served.  It seems that someone who should know and understand what you need is suggesting a different assessment to see if you won't do a lot better, or even just a little.

I use a low fixed pressure, as that is what my physician determined.  It meant I could get away with the Elite model (the brick-that-has-telemetry and an SD card).  So far, my numbers rarely exceed an AHI of 2.5, and my month-to-month average over five years is 0.7.  Not too shabby.
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RE: Benefits of Fixed Pressure??

No Problem. I hope you find your laptop soon.

Clarify what the sleep study will be ahead of time. The sleep studies with titration that I know of are split studies with about 4 hours of study; then titration (increase pressure) until no event. I don't know if the study is continued after that.

Hopefully a Bi-level is used.
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RE: Benefits of Fixed Pressure??
Yes, that all makes sense.
The trouble is that I don't trust that the sleep doc has listened to me enough to know what might improve my sleep quality (as evidenced by loads of incorrect information in her notes).
So, I asked for and received some information here.

Yes, I already clarified what the sleep study is. It's a full polysomnography with the cpap all night.
I doubt they will use bi-level since the doc ordered fixed pressure titration.
My first sleep study was supposed to be a split but they didn't put me on cpap during the last half so I didn't get titration.
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RE: Benefits of Fixed Pressure??
CPAP has one fixed pressure it can still have EPR were the IPAP is the set pressure and the EPR is subtracted by the amount set (Off, 1, 2, 3) to give the EPAP value.

Using the ResMed AirCurve 10 VAuto as an example:

From the manual: [In S mode, you may set two treatment pressures-–one for inspiration (IPAP) and one for expiration (EPAP).] The difference between the two is the Pressure Support (PS) which can be set from 0-10 cm. PS is like EPR but can only have a difference of up to 3 cm.

Both also have Autoset with variable pressures.

(Not talking about Central events.) This is from ResMed titration guide.

CPAP titration:

Increase CPAP ≥1 cm H2O every ≥5 mins for obstructive apneas, hypopneas, RERAs and at least 3 min of loud or unambiguous snoring.

Observe patient and document final settings; be sure to document
the final CPAP pressure, EPR setting (if any) and ramp time


S-mode titration: Resmed's AirCurve 10 S is fixed, VAuto has S mode, VAuto mode and CPAP mode.

New Patient:
Initial settings:
IPAP = 8 cm H2O
EPAP = 4 cm H2O

Patient been on CPAP
Initial settings:
IPAP = 4 cm H2O above EPAP
EPAP = CPAP level at which obstructive apneas were eliminated

For obstructive apneas:
• Increase EPAP by ≥1 cm H2O every ≥ 5 min
• Increase IPAP to maintain 4 cm H2O difference between IPAP/EPAP

For hypopneas, RERAs or snoring:
• Increase IPAP ≥ 1 cm H2O every ≥ 5 min until resolved

For SpO2 < 90% with all respiratory
events eliminated:
• Increase IPAP by ≥ 1 cm H20 every ≥
15 min until ≥ 90% SpO2 is reached
• Follow sleep lab protocols for adding O2

Observe patient and document final settings, including IPAP/EPAP pressures
and TiControl settings if altered from default
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