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Low AHI, but still feel terrible - Printable Version

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Low AHI, but still feel terrible - Trizz - 11-19-2020

I was diagnosed with moderate obstructive sleep apnea in July of last year (AHI of 16.4). Since then, I have used my CPAP nearly every day with fluctuating results. Most days are around the 1 to 2 AHI range, with the occasional night getting above 5 (1.95 average AHI over the last year). Judging by the numbers, I should be feeling much better; but I still struggle with many of the same symptoms I had prior to getting on CPAP. The intense brain fog, memory issues, headaches, and fatigue just have not gone away. I'm wanting to start taking a bit more of an active approach with my CPAP therapy to see if there is anything else that I could be doing to help decrease my symptoms. I would greatly appreciate any help that anyone could provide. Based off of my OSCAR snapshots, does anyone see any adjustments I could make that would help?


RE: Low AHI, but still feel terrible - 2SleepBetta - 11-20-2020

Hello and welcome to the ApneaBoard Forum, Trizz

Others better qualified to help you will chime in, but here's a response more than 24 hours after your post.

I recommend you raise the lower pressure from 6 up to 7.5 and doubt that will be enough, but it is a sizeable jump and your real CA events may increase. I suspect the few CA's you show are not true CA's, but just an after affect (breath holding?) close after an arousal (such as are marked by sudden and brief increased amplitude flow rate waves preceding the CA).

You need to post enlarged views of the FR curve that are about 2-minutes in width (vs entire hours of sleep as width is now posted) and expand those graphs to make the normal breath wave be about 1-inch in overall height (while including in the graph enough vertical coverage to show the entire wave burst). Do views that include a CA toward the right side of the view and show preceding breathing to the left. Then take a 2-minute shot in what appear to be most normal breathing as well as where breathing is continually irregular near the large bursts of amplitude.

You report a common problem: unrestful sleep with low AHI. It often takes and is treated by a bi-level machine like the AirCurve VAuto. Those address the matter with greater pressure support than the EPR of 3 that you are using and enable one to exhale more easily against higher pressures. The higher low pressure helps maintain sufficiently open/expanded cross sectional areas of your airway, particularly at the critically restricted airway points. Those points may continually restrict your breathing and require you do too much work to inhale--do work somewhat like sucking hard on a straw for air.

Here is an example of a FLow Rate curve that shows continual flow limited breathing but no flagged flow limit. Why no flag? To be flagged there would need to be a significant decrease (significant change)  in the inspiratory air flow before a flag is triggered. As you can see, the areas enclosed between the inspiratory half waves and the 0-axis continues nearly constant despite what appears to be continuous restriction. I'm guessing you may see a lot of deformed inspiratory flow, but not necessarily the same shape as I show from my own curve.


Here are machine setting and posting links that indicate their relevant subject:


RE: Low AHI, but still feel terrible - Sleeprider - 11-20-2020

I completely agree. You are set at 6-16 pressure with EPR 3. Since the minimum pressure is 4.0, you are at minimum EPAP pressure and getting less than 3 EPA most of the night. Elevating minimum pressure to 7.0 at least gives you the full range of EPR you have set. I see a lot of spikes of inspiratory flow rate through the night, and suspect these are arousals. We could zoom in on them to confirm. The higher pressure and EPR may help to reduce those arousals. I actually think you should consider dropping EPR to 2, and still using the minimum pressure of 7.0. This should totally stabilize pressure, and minimize the sleep disruptions. Therapy looks great with low AHI and leaks, but I think a higher pressure and lower EPR should resolve what residual events we see in these charts.

RE: Low AHI, but still feel terrible - Trizz - 11-20-2020

Thank you guys so much for your replies! I will definitely try bumping up my pressure tonight and drop the EPR down to 2 to see if that helps any. I've attached screenshots of a zoomed in view of a CA and another of an arousal that wasn't flagged as anything.


RE: Low AHI, but still feel terrible - Sleeprider - 11-20-2020

I think the new pressures should work out fine for you. The CA events are all preceded by a sigh or unstable respiration, and are of minimal duration. Both closeups are at or above 7 cm and show you probably don't need the EPR at 3. Sleep well, let's see how it goes.

RE: Low AHI, but still feel terrible - 2SleepBetta - 11-21-2020

After seeing your low levels of flow limiting effects in 3 and 4 minute views I concur with SleepRider you should focus on reducing arousals. Your arousal index (as if there were one) would likely be in the neighborhood of 2, but many of those are (or nearly are) coincident with indicated CA, right or wrong.  "Hard work" of inhaling for any long period seems unlikely for you. Such work can cause arousals that double up with such work in having doubly detrimental effects against sleep.

If there were a lot more raggedness, in the degree and frequency of it in your FR tips, that would also call for trying higher low pressure and more pressure support, the latter being limited so as not to unduly increase CA. As hoped and would be expected, if SR or other expert help weighed in here, you'd get a more balanced recommendation and I would learn more as you and I have, Trizz. I'm looking forward to seeing your next graphs.

Int the weeds: Your expanded views show a minimal level of unflagged flow limiting effects in the inspiratory curves: Nov. 3rd, 4:24:24-26; 4:25:10-20. Nov. 18th, 4:06:10; 4:06:34. Those are slight and few.  The attachment shows the more serious forms, but even those, if you had them, may not have significant effect if they are not continual. I post the graph only because it illustrates both normal forms and  irregular, more troubling wave tip forms and their relative significance if you should notice a lot of the more serious ones of them in your FR curve peaks. That would indicate you do extra work in breathing and the likelihood of more arousals.