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Auto SV settings and Periodic Breathing in REM

After weight loss, I no longer have many obstructive apneas as I did some years ago, but I do have some centrals. In particular, I seem to go into periodic breathing during REM sleep. This doesn't cause significant O2 desaturations, but I wake up feeling pretty beat up and unrested, and that's the only abnormality I can see. 

I have a tendency to hyperventilate as well during REM, with the breathing rate getting shallower and faster; I'll often wake up sweating in the middle of a dream, and the cpap data will show I had been hyperventilating for awhile. Actually, the better part of a decade ago I had to quit bilevel therapy because it would induce rapid-deep breathing and give me extreme hyperventilation, 30 deep breaths per minute.

Just lately I've acquired a bipap Auto/SV to see if it might enable me to smooth out the periodic breathing... which isn't dramatic but is very visible as a waxing/waning pattern...to see if that might allow me more IQ points in the daytime.  And clearly it did smooth out the PB flow on the first few nights I used it. And it does not drive me into hyperventilation like a regular bipap will. 

But after a few days it seems as though the algorithm is now just adding pressure support to every breath, whether there is PB or not. This makes for a very high pressure if a high max PS is set, and doesn't even out the PB.

So I am now trying PS set to Min:0 and Max:3, just to keep from getting discomfort and mask leaks from a lot of pressure support I don't need. But it isn't compensating for the PB.  Any thoughts from you periodic breathing experts out there?

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Hard to say, but maybe increase the PS max in increments. Your could try turning off BiFlex and using a rise time of 0. This will give you a faster onset of pressure support all the time, but it might help with periodic breathing by making the machine faster to instill IPAP. That is a comfort feature, and you can set rise time from 0 (fast) to 3 (slow). Trigger sensitivity is settable on some machines, but I'm not sure about yours. Higher trigger sensitivity decreases the amount of air needed to trigger IPAP. The default is 6 mL. With a more sensitive trigger, IPAP is started with less spontaneous volume, and this can help some people get into the IPAP faster.
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Thanks, increasing the PS in increments is exactly what I'm trying first. My actual EPAP is fine set at auto from 4-5.5. Tonight I'll use a PS range of 0-4, up from 0-3 last nite.

I tried it with flex off the other day - and found that I'm pretty spoiled, it was some effort breathing against the pressure, and I tend to have a hard time falling asleep. I even added .5 PS as the minimum, but it still seemed hard to breathe against, which surprised me.  So the flex is back on at 3.

This is a new machine for me, but I'm not sure I can adjust rise time while keeping it on the AUTO settings. I'll see. I don't think "trigger sensitivity" is something built into this machine, it's not mentioned in the stuff I've read. 

all good logical advice, I'll play around with it... thanks.
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