Are these flow limits my problem?

[Sleeprider]

K888, the January 9 chart is a mess with lots of positional clusters. Higher pressure may break through the obstruction, but I disagree that "some individual spikes from about 5:15-6:00 am that were handled by that pressure." It would have probably been better to awaken and adjust whatever was causing the positional apnea here. I don't see the higher pressure as stopping anything.

[k888]

Thank you Sleeprider and SingleH.  I will keep the pressure at 15 and slowly increase PS, keeping the collar of course.  I really appreciate the guidance as, even though I am learning, reading the detail on charts is pretty advanced.  

SingleH, the link about pulmonaary and upper airway flow limits is interesting, but may only apply to an ASV machine, not a bilevel – not sure about that.  I will keep your experience with PS & centrals in mind.  In fact, your comments about that in another thread were one reason I was approaching change slowly.  Many thanks to all, k888

[k888]

Update:  I decided to inch up on pressure to see if I could build up some tolerance, and increased max IPAP from 15 to 15.2 (Jan. 17).  I woke up to blowing and changed it to 17, which previously had both worked and not worked.  More blowing.  I was pretty sure that turning it back down to 15 would result in a string of events, so what the heck, I set it at 20.  And went back to sleep.  More blowing in early morning, so I changed it to 23 and, just in case, rotated my collar.  Chart posted.  Flow limits poor, but the higher pressure, at least to 20, seemed pretty effective.
   

On Jan 18, I set the max IPAP at 23 and increased PS by .2 to 4.6.  Early part of night good, second part not so good, then I rotated collar and things improved.  The Jan 19 settings were the same, but I rotated the collar for the entire night.  Results were pretty good except for last thing in the AM, not sure what that was about.  Re the collar: I start using a new corflex collar as intended with my chin in the dip.  When it appears to begin failing, I turn it upside down as that effectively increases the collar width.  When that starts to fail, I rotate and use the sides.  They are less comfortable as the velcro overlap is in a bad spot, but it does extend the life of the collar.  At the moment, I have used this particular collar for 15 nights.
[attachment=58627][attachment=58628]

So this is what I believe I am seeing:  Higher pressures help & I still need a collar, and have to be alert to collar failure.  I don't really like the higher pressure, aerophagia, or part-time chipmunk cheeks that come with higher pressures, but they aren't really much worse than the prior blowing of long strings of events at lower pressures, maybe better.  I do think I am waking up more in the latter part of the night, possibly because of the pressure differentials?  I am inching up on PS.  I saw a real improvement on flow limits when moving to the Vauto with PS of 4.  This seems especially true in terms of the amount of the night impacted by flow limits, which I do not think is reflected in any of the flow limit stats.  I do still see a lot of "malformed" breaths during the longer strings of no-event periods, so I hope the PS increases relieve that.  I will say that I felt rather less sleepy over the last couple of days, even though my AHI is not as good as some of my prior best.

I would greatly appreciate your observations and any suggestions on how to improve this/move forward.  Many thanks, k888

[Sleeprider]

You increased maximum pressure. If you want to get ahead of obstruction, you need to increase minimum EPAP pressure. Given that most of your obstructive evens and clustered, I don't think it is going to be a solution. I'm sorry to see you are having such a hard time maintaining effectiveness with the collar.

[SingleH]

Hi, k888, from what I can see your flow limits are generally under control and then there are large spikes with accompanying increases in pressure from the machine as it responds.
I think as sleeprider mentioned earlier that this might be positional related stuff, as the rest of the your time you have periods of no events and no flow limits.
I would definately check your collar but also to be careful to not have the collar too tight. Have you tried a chinstrap to see what if any effect that has? Also check how your pillows are setup, do you have anything that could be causing a problem when you roll onto one side.

It doesnt look like you need higher pressure support when you dont have those extreme spikes in flow limits, but in the meantime you could try increasing PS while you are troubleshooting things just to see if it helps. Only make small increases of 0.2 and then leave it like that for a few days for your body to adapt. Other than that I think you need to check on your pillow, collar, strap setup.

[k888]

Thank you Sleeprider and SingleH for your comments.  

If I were just beginning the CPAP process, then the absolute right advice would be "get those positional apneas under control." But I know I have positional issues, and I have been working on it for some time and with great effort.   I do not believe they are the only issue, and in fact they may be masking other issues.  

Respectfully, I have to point out that:
•  All three nights show substantial flow limits even during long runs of non-events.
•  I do understand that EPAP addresses events.  But (this is really a question,) since the machine algorithm causes pressure to rise in response to/after an individual event, then presumably there is a reason for this.  I have assumed that the pressure response is intended to help prevent additional apneas.  Am I wrong about that?  If I am wrong, then what is the reason for pressure increases?  And if I am right, then there are multiple single events over these three nights where the machine response is greater than the 15 max IPAP I was allowing it.  

If I can weed out the non-positional events, then it helps clarify the situation and also incrementally improves my sleep.   k888

[SingleH]

I am only speculating as to the causes of those events but for sure it doesnt mean my opinion is correct.


EPAP is intended to help prevent additional apneas and you can see it increase in response to a number of these. If you are still having clusters of apneas, you may want to try increasing your EPAP further.

Regarding the pressure increases in response to flow limits. I believe the machine increases pressure to combat flow limits, when you have significant flow limits the machine is responding to this and increasing IPAP and in turn EPAP follows this.

I dont know the max 15 IPAP figure is you are referring to. Your Max IPAP is 21, your max EPAP is 21- PS (4.4) = 16.6 EPAP

Ultimately to combat the apneas, a higher EPAP will address problems and result in less situations where the machine is having to climb pressures to address apneas. To combat flow limits you need more PS and your current PS is stil fairly low so you have lots of room to work with.

Outside of further positional work, if it was me, the test I would do next is increase EPAP to 8.5 and increase increase PS to 4.6.

[k888]

Thank you SingleH,
I appreciate the advice.  I am new to the bilevel, so it is good to know that I am well within the PS parameters.  I had my max IPAP set at 15 until a few days ago because I could not tolerate higher pressures.  It took me a long time to realize that the intolerance only kicked in when a positional apnea caused constant blowing at the highest setting.  Short of that situation, it seems I can tolerate higher pressures and it actually helps.  

I just updated my profile.  PS was actually 4.6 and I went to 4.8 last night.  AHI was under 2 and flow limits improved some.  A few positionals.  I know I am not "there" yet, but it seems to be moving in the right direction.  k888

[SingleH]

The thing to remember with the Vauto is the relationship between Pressure support and the max IPAP. The pressure support is like a fixed range that is on a sliding scale. A band that moves up and down.

As it is the EPAP that clears apneas, if you have max IPAP too low the vauto cant move the "PS range" high enough to clear the apnea. You need to incrementally increase max IPAP inline with your PS changes.

For example, lets say most of your apneas as cleared by an EPAP of 15. And your current PS is 5 and max IPAP is 20, you slowly increase your PS to 6 whilst leaving your max IPAP alone. If you do this the max EPAP the machine can reach is only 14 (Max IPAP 20 - PS 5 = Max EPAP 14) If this happens your machine can never get to the optimal EPAP of 15 which you need to clear apneas. So each time you increase PS, increase Max IPAP accordingly. Hope that makes sense.

[k888]

Thanks SingleH.  It does finally make sense.  And it's a simple three digit equation, but when you aren't certain of the correct fixed value of any of those three digits, the math gets more complicated.  Nevertheless, it starts to sort itself out.  (–:
k888