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Sensitivity to small pressure changes
#1
Sensitivity to small pressure changes
I have been struggling with CPAP for over a year. I've always had good numbers so optimizing therapy has been really hard for me. I went on bilevel a month ago, started on 16/10 PS 4 VAUTO. This didn't seem to make a difference so I've been experimenting with different settings. I had a pretty good night two nights ago, I felt like I slept well but still didn't feel completely normal.  My pressure settings were fixed EPAP 10.4 IPAP 14. I should also note that I turned off CA detection just in case this was causing me problems. The UA are almost certainly CA events. I have very rarely logged OA.
[attachment=9789]


There looked like there were some flow peaks that indicated flow limitation(my flow limit graph was zero all night though) so I made a tiny adjustment last night and increased to EPAP 10.6 IPAP 14.2. At PS >= 4 I noticed an increase in CA events so I thought a small increase in total pressure was a better idea than increasing PS. There was a substantial difference in my flow rate graph, aerophagia was really bad this morning, and I woke up feeling worse. 

[attachment=9788]

1. Is this something that my body might get used to if I leave it on or should I drop back the pressure to 10.4/14? 
2. Do those peaks in the first nights diagram indicate flow limit?
3. Looking at the green line from the first diagram, this paper describes that type of shape as a collapse in the airway followed by a reopening of the airway. If that was the case I would expect mask pressure to increase during airway collapse, and decrease when the airway reopened. However it looks like mask pressure does the opposite. Any idea what this means?
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#2
RE: Sensitivity to small pressure changes
What is your Timin and TiMax? I think rise time setting is grayed out with this mode? As you can see with EasyBreathe off the flow is generated as a square wave. If the flow is dropping to EPAP before your inspiration is complete, then the breath will appear flow-limited as the support drops out. The answer may be to increase TiMax.
Sleeprider
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#3
RE: Sensitivity to small pressure changes
Thanks for fast response, Sleeprider! Timin /Max are 0.3/4.0. 4 is the max but I don't think I'm reaching that anyway. I'll have to double-check when I get home but I'm pretty sure I can edit rise time. Right now it's on min. If I could edit this, what would you recommend?
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#4
RE: Sensitivity to small pressure changes
4.0 would be unusually long. Even people with fairly high tidal volume are generally in a range of 1.8 to 2.4, so that surprises me.
Sleeprider
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#5
RE: Sensitivity to small pressure changes
0.3 / 4.0 were the default settings that came with my machine. Isn't Ti Max just the maximum allowable time at IPAP before it drops pressure, if the machine detects expiration before Ti Max it will drop to the EPAP pressure anyway? Would you recommend changing either of those settings and/or change rise time?
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#6
RE: Sensitivity to small pressure changes
That's true, but unless you're dealing with COPD or other issue that requires an extraordinary inspiration time, it can't hurt to turn it back to something more normal. Try 2.4 and lets see if it makes nay difference.
Sleeprider
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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#7
RE: Sensitivity to small pressure changes
Ok will do and report back tomorrow
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#8
RE: Sensitivity to small pressure changes
I went back to 14/10.4 last night and turned TiMax down to 2.4. I fell asleep on my arm and eventually woke up with it completely numb, I also had another awakening to use the bathroom. I don't feel like I slept well. I attached my sleepyhead chart from last night, zooming in on an UA. The UA is surrounded by about 12 other areas where flow rate stops but not for long enough to be marked as an event. Could these cause arousals? What adjustments would you recommend for these?

[attachment=9796]
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#9
RE: Sensitivity to small pressure changes
Had another bad night last night(at least I don't feel good today). Maybe all the leaks caused arousals but I also had some strange flow rate graphs that I don't quite know how to interpret


[attachment=9810]
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#10
RE: Sensitivity to small pressure changes
Close-ups are ok but I would add a chart of the full night to provide context.  

What I see is last night had twice the breathing rate of the previous night.  Why???
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter 
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