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APAP behavior puzzling to me
#21
(12-27-2014, 11:01 AM)quiescence at last Wrote:
(12-27-2014, 10:30 AM)sgearhart Wrote: Looks like I going to have to constrain it ...

you mean like 8 to 10.5 with ramp of 30 minutes?

You got it!
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#22
Hi sgearhart, since you stated that you were set at 10 cm H²O before this experiment with APAP started, why wouldn't you try APAP set at 8 ~ 10 to constrain the upper limit to the former setting that worked pretty well?
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#23
(12-27-2014, 11:16 AM)surferdude2 Wrote: Hi sgearhart, since you stated that you were set at 10 cm H²O before this experiment with APAP started, why wouldn't you try APAP set at 8 ~ 10 to constrain it to the former seting that worked pretty well?

I was hoping to have a reserve pressure boost for those occasional OS's but the S9 in not playing well with others.
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#24
Yes, but in doing so you may get the same CA appearances since you are increasing the pressure. No big deal, but sometimes just a slight change in top set pressure can produce untoward effects.

My past experience when doing almost the same experiment that you tried resulted in interrupting my effective therapy and making it take over two weeks to get back to satisfactory reading when I returned to my previous settings. I went from CPAP set at 14 cm H²O to APAP set at 9 ~ 15 cm H²O and got a huge cluster of welcoming CA events (even some OAs) right when the machine initially ramped up the pressure while I was awake. It went straight to 15 cm H²O so I suppose it always wanted that much pressure when I was doing straight CPAP but I wasn't letting it have it. Lesson learned, leave well enough alone or make very tiny changes when experimenting.

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#25
It is also entirely possible that the CA's you are experiencing are nothing more than an adjustment period to the new level of pressure. It seems to me that maybe the speed at which the changes are happening are not giving you enough time to adjust. Just a thought to possibly open the top to 12 and leave it there for a week, take the risk that even though the first few nights may see a higher CA rate that after that they will settle back as you adjust to the new pressure. There are times where you can make an adjustment, see a change, and attribute it to one thing when it was another. You may be linking the cause and effect even though they are unrelated. Possible you just had a bad night and a spike in CA, having no link to the new pressure, and even if it is cause and effect maybe if you try a week or two you might adjust and see a much better result. Not all of my tweaking has resulted in immediate positives, and yes at times I have made it worse for a week or two trying something different, but if you don't try and give it enough time to have a positive effect you might miss the chance. Just my thoughts from my personal experience, as they say YMMV.
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#26
(12-27-2014, 12:14 PM)Galactus Wrote: It is also entirely possible that the CA's you are experiencing are nothing more than an adjustment period to the new level of pressure. It seems to me that maybe the speed at which the changes are happening are not giving you enough time to adjust.

That's my thinking, too. I started with a constant pressure of 17. Since I have an AutoSet machine, I collected a month of data and set it to Auto mode at 15/17. I've since backed it off to 14/17. I almost never see more than one event per hour and often have an AHI of 0.2 or so. I see no reason to ever change the upper bound but I want to slowly and gradually back off the lower setting as long as I'm getting the same results. Unless my numbers go off the rails, I wouldn't want to do more than one very gradual change per month followed by a careful review of the outcome.
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#27
The machine wont raise pressure in response to CAs. So its raising it in response to OA type events. However if even in the sleep lab you were getting CAs over a certain pressure your in a catch 22.

I have OA and in the sleep lab titrated at 15. With no CAs. However on a home machine I will occasionally toss a CA or two even now. Sometimes at auto min of 9. About all a home machine can do is tell if your airway is open or closed. If you dont breathe after the time it thinks you should itll flag a CA. Clear Airway Apnea. Without the brainwaves there is no way for the home machine to know if its a true CA or just your head trying to get in sync with the machine and you not breathing when the machine thinks you should.
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#28
In my ongoing efforts to regain the ability to sleep on my back and tolerate the extra pressure required, I perform one hour sessions while sitting in my chair and watching TV. I notice that it often flags several CAs, which I can appreciate, but it also flags an occasional OA. That confirms the advisability of performing the AHI calcs the way I do mine as opposed to taking the machine readout as being the gospel. I have a very good idea how long it takes for me to fall asleep and certainly know when I wake up. When I toss out any early and late clusters (first 45 mins.), then compile my own version of the AHI based on the remaining time and events, I get something much closer to reality.

That can save you lots of time chasing your tail trying to reduce your AHI as the machine mistakenly reports it. These machine are remarkable but they aren't perfect. I have learned a lot about their weaknesses in reporting by doing these awake sessions. Swallowing, coughing, talking, exerting while rolling over and several other actions can and do cause events to be flagged. They are usually CAs but I have seen several OAs flagged while doing some of those acts mentioned. In addition, as you would expect, simply holding ones breath for ten seconds will get you an OA flagged any time you care to create one. I don't suggest you use that to game the home reporting SD card system but I suspect it has been done. You couldn't fool a sleep lab though since they're on to that and use a skull sensor to get your brain wave to see if you're actually asleep. Too bad a CPAP machine algorithm can't tell when you're sleeping.

IMHO, If you have a couple or three short term OA in an hour, it's not worth much effort trying to squelch them since you are in an area of diminished returns.

Best regards, Dude
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