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Side vs. Back sleep - APAP tuning
(01-31-2015, 12:11 AM)TyroneShoes Wrote:
(01-29-2015, 04:32 PM)crwheelr Wrote: ...I suspect that obstructive is only happening while sleeping on my back. During those moments between awakeness and sleep I have on occasion sensed my airway closing, like a valve would snap shut. Is this true or mostly true that obstructive apnea happens only on back sleep?

Be that the case, we would want an APAP algorithm that could adjust quickly to the breathing pattern changes as one shifts sleep positions. If on side, the PAP should be able to settle into the low limit setting an stay there. A transition to sleep on back - the tool should be able to ramp up rather quickly on the first or second event so as to minimize total obstructive events while sleeping on back.

Can an S9 Autoset pressure "gain" be adjusted (maybe maximized), so that when obstructive events start (move to sleep on back) the pressure will increase quickly to maximum limit?...

For many patients, obstructives happen regardless of sleep position. It seems to me that such an algorithm is not practical, nor any more helpful than what we have now. It also does not seem to be either safe or therapeutic to raise pressure when there are no events to warrant it.

It also seems that the only way it could even tell if you were on your back would be if it could see you. It needs a infrared camera and optimal positioning, plus a guarantee of no false positives. None of that seems practical, and it is sort of Big-Brothery to boot, not to mention probably a pretty expensive upgrade.

Assuming we could even get over those hurdles, if you designed the APAP to have a slight difference in the pressure range when on your back, that might be OK, but the less aggressive the change would be the less effective it would be, and the more aggressive the change would be the riskier it would be. And it does not seem like there could be a sweet spot where added risk is low and efficacy is improved all that much.

Assuming you need more pressure when on your back, which may be true, or may not be true, the APAP mostly does this already; it is designed to provide more pressure when you need more pressure, but in response to events, not in anticipation of them. It is also smart enough to do this without having to know whether you are on your back or not. If you need more pressure, it gives it to you; knowing whether you are on your back or not is not relevant to knowing when to give you more pressure; it knows how to do that regardless.

Anticipating an event simply because you rolled onto your back and raising pressure to prevent it could be good, but the drawback is that raising pressure always runs the risk of creating CA events. Medicine errs on the side of caution, which is sort of what the "first do no harm" thing is all about.

That said, nice out-of-box thinking. Could you find someone to fund a grant to study whether this would be a worthy pursuit? Would it turn out to be significant enough to inform APAP design? My best guess would be no to both. But I would be happy to be proven wrong.

Tyrone, Hey appreciate your feedback here. Since my posting I have been further studying my patterns and did notice a pattern to your comment "but the drawback is that raising pressure always runs the risk of creating CA events". at the higher pressures around 14/15 on my S9 I see this highly periodic with sinusoidal-envelope flow pattern followed by CA event. Its like my body is getting too much oxygen and decides to stop breathing, only to have to catchup after the 10-15 second CA event.

Another observation, with CPAP sleep, I find myself waking up on my back way more often then without. Signifying to me that I am spending more time on back than before.

Can anyone suggest a definitive guide to tuning? I have been checking my detailed flow patterns daily and adjusting pressure ranges at 3-4 day intervals trying to find my sweet spot. Best achieved was around a 7 index but not repeated nights after. There does seem to be other sources of variability that affect the index. I am trying to control those sources as I estimate them: Keep the same hours of sleep, no coffee after noon, room temperature and humidity controlled, confirm mask tightness so no leakage - yet my index varies pretty wildly.

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(01-29-2015, 07:33 PM)OpalRose Wrote: Greetings,
I am a side sleeper, but now and then I like to sleep on my back. I was never able to sleep on my back prior to CPAP because I felt as if I were suffocating. We had to replace our bed this year, and deceided to purchase an adjustable bed. Yes, it was expensive, but worth it. I find that if I raise the head just a little, I can sleep on my back, and my AhI doesn't seem to be affected. I would guess that if I wre laying flat on my back, my readings would be high.

I'm with OpalRose on this all the way. I could never sleep on my back pre-cpap. My official in clinic test results were as follows: Apnea while on side, not so much... apnea while on back? Forgetaboutit!

But now I can sleep on my back, on my side, on my puppy. Really anything I want to do. I thought I had discovered a new toy when Herb pointed out to me that with cpap, we can even sleep under the covers! Wow, how cool is that? I do keep my top side elevated though. Once in awhile I scoosh way down in the covers so I'm flat (or as flat as I get, which when on my back looks very much like a boil on a railroad trestle.) But I don't do well unless I go over onto my side. Then I'm fine. Elevated? I'm good to go on my back.

What a joy that is.

p.s. Mongo's right about a tight range. Check where you stay parked the majority of the night and if it's in the area of 10+, then raise your minimum a couple of notches.

p.s. Surfie? Your back sleeping is a mess! I think Mrs. Surfie needs to hang you in the closet overnight.
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I'm now a side / back sleeper , I used to like sleeping on my stomach (Belly) but now dawning the mask it's almost impossible due to the dreaded leaks. Back of course has the least amount of leaks and for me I find it almost impossible to know how that effects my AHI's , when I look at my data it's hard to remember my sleeping position.
Anyway for me I'm sleeping where I'm most comfortable and letting my machine do it's thing, and enjoying a nice night of sleep!
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(01-29-2015, 07:18 PM)quiescence at last Wrote: Yes, studies show most tongue, soft palette, throat obstructions are much worst when the tongue weight is falling into the throat (back sleeping). There are other weight and size of clear throat area issues that complicate, but usually result in same thing, position that is the worst is usually on the back. nasal cavity obstructions may not follow the same course, as they do not relate to the tongue weight.

It is a very clever thought of doing some sort of detection and auto gain titration algorithm.

I am awarding you the very first Excellence Toward QALity in Sleep Award.

This idea ought to be easy to integrate into next generation ALLPAP machines! In a few years our data capable machines will be dinosaurs.

What will be necessary for the detection is a device that has multi-axis accelerometers allowing home detection of sleep position.

Now if only the detection device could also detect EEG info and transmit position and brain waves all to the ALLPAP wirelessly, and ...

if the ALLPAP was a learning device that correlated the position and EEG with the detected apneas, auto-deciding the appropriate up and down signals or jumps.


Hey thanks for that virtual award!! I do think that sleep position sensor built into the masks might go a long way to prevent obstructive for all cases of sleep position. Furthermore, I believe that with such a sensor, it might no longer be necessary to run the machines in adaptive mode anymore. once a subjects characteristics are learned, its strictly the position sensor that would dictate control pressure. Subjects could periodically recalibrate as result of weight gain whatever.

So next just to prove positional dependence I am getting my iphone video running in timelapse mode as available on several apps...film myself against time of day caption and correlate that with my trace. I will report back in a few days.

If it does prove out that back is considerably worse regarding necessary control pressures to avert obstructive (and running that risk of oscillatory/unstable breathing as I reported earlier), well, I might just go the sow the tennis ball to back of neck approach so I never back sleep Smile
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(01-30-2015, 04:55 PM)saltydawg2 Wrote: When you say, Paula02, that your centrals go up on your side, I can relate. I can look at my graphs and can tell when I roll over onto back, or side. Last night OA was under 2, but centrals were twice that. So, no real satisfaction patting myself on the back for low OA, sleeping on my side, when centrals were jacked, huh?

I am not sure about this but maybe others can correct me. The machines do not up control pressures on CA events. I interpret this that the body has enough O2 and pauses the breathing function. when O2 drops, breathing resumes. I think maybe this is just the normal living condition for healthy people. I say this because I can wittingly sense CA events just while laying in bed, relaxed and watching TV (now that I am totally tuned in to the breathing thing). So CA events - lovely, so long as the overall breathing pattern is stable and not triggering CA's every minute or so.

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(02-27-2015, 03:58 PM)crwheelr Wrote: I am not sure about this but maybe others can correct me. The machines do not up control pressures on CA events. I interpret this that the body has enough O2 and pauses the breathing function. when O2 drops, breathing resumes. I think maybe this is just the normal living condition for healthy people. I say this because I can wittingly sense CA events just while laying in bed, relaxed and watching TV (now that I am totally tuned in to the breathing thing). So CA events - lovely, so long as the overall breathing pattern is stable and not triggering CA's every minute or so.

I think you'r partly right. Simplistically, central apneas can be triggered by an imbalance of O2 and CO2 in the bloodstream. It requires a certain level of CO2 for the brain to send the "breathe now" message to the lungs and diaphragm. If the CO2 is too low (eg when first adjusting to CPAP) then the message doesn't get sent and a central apnea results.

On the other hand, central apneas can also result from problems in the brainstem or nervous system, or from medications (particularly opiates). Idiopathic central apnea is just as serious a condition as obstructive apnea and can't be ignored. In fact it may be a symptom of a more serious underlying condition such as congestive heart disease (especially when accompanied by Cheyne-Stokes respiration).

What you're describing as central apneas when you're still awake are really just pauses in breathing, and not a problem. They can often occur as you transition in and out of sleep. PAP machines can also record "clear airway" apneas which are just pauses caused by yawning or perhaps while moving around in your sleep. These are usually just one-offs and not a problem.

There's a good discussion of central apnea on the Mayo Clinic site - Google "central apnea causes".

You're also correct that ordinary CPAP machines don't respond to central apneas - you need an ASV type machine (automatic servo ventilation) which will kick in quickly to keep you breathing at a predetermined rate.
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I just posted a thread about positional apnea, so you might read that? I am not sure, but I am trying an experiment using kids swimmies attached to my sleep bra to keep me from rolling over. My AHI is super super low when on my side and all my events seem to occur on my back. I go for my new study at the end of March and hopefully will have information that will help me work with my doctor.
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