Am I still having flow-limitation? Persistent fatigue & insomnia.

[gpenz]

Hi everyone,

Background about my OSA, PAP history, symptoms, and general health
I was diagnosed with OSA (AHI 16, nearly all hypopneas) in 2020, after having bad insomnia for a long time (waking up for hours in the middle of every night, as well as unwanted early-awakening). I've been using PAP continuously with ~100% compliance since February 2021, and it has been somewhat helpful, but I am still having persistent fatigue, insomnia, and other symptoms associated with sleep issues (trouble focusing, anxiety, mild depression). Aside from that, I'm a fit and healthy man in my early 30s with no other health issues and not taking any medications. I prioritize my health, sleep hygiene (double blackout shades, cool bedroom, morning sunlight, etc.), exercise daily. 

I could write a lot about all my experiences with providers and the things that I've tried, but I'll keep it short. The first sleep specialist I saw told me that it was impossible for me to have sleep apnea, since I was young and fit and a healthy weight. I went through a frustrating process of being told to work on my sleep hygiene despite it already being nearly perfect. I saw a sleep psychologist who encouraged me to demand a sleep study, and low-and-behold, it came back positive for sleep apnea. I started out on APAP, then CPAP, and in Dec 2022 switched to ASV since I learned from Dr. Barry Krakow that ASV can be more comfortable and more effective for patients such as myself who more closely resemble the "UARS" profile. I also added a custom MAD (Mandibular Advancement Device oral appliance) that I used at the same time as my ASV. I had a second in-lab overnight sleep study in April 2023, while using my ASV + MAD, to evaluate the effectiveness, and the results came back with 0 AHI and 0 RDI (though I only slept 4 hours), and the Dr. said that my breathing is "perfect". But I continue to have persistent fatigue and insomnia (primarily early awakening), and am now considering pursuing MMA surgery. I had a DISE that showed complete tongue base collapse, and the Dr. who performed the DISE told me that I have "a TON of obstruction". I have also stopped using my MAD since it caused jaw pain and bite issues. 

My primary question is: is it possible that my sleep-disordered breathing (SDB) is not being fully treated by ASV? 
I have not experimented a lot with changing my pressure settings, since my Dr.'s discouraged it, and I also tried several times increasing the pressure but found that it induced more aerophagia, which I found uncomfortable. 

Attached screenshots
I'm attaching several screenshots from a recent night's sleep on Nov 23rd 2024. Two screenshots are zoomed in on the flow-rate graph so you can see the flow profile of individual breaths. Do these breaths look flow-limited? I'm seeing a lot of what I believe might be "class 2" and "class 4" flow limitations. One of these screenshots is from early-on in the night, within 20-30 minutes of falling asleep, where the pressure is relatively low. The second screenshot is later in the night where my pressure increases. 

Next steps/experimentation/questions
-I have started an experiment to increase my PS by 0.4cm, every 3 nights, and am planning on seeing how I feel as well as monitoring my flow rate graph for flow-limitation. Is 0.4cm every 3 nights too fast or too slow? I have seen various recommendations, ranging from "increase pressure no more than 0.5cm every 1-2 weeks" to "increase pressure by 1cm per night". And when you get a titration study, they increase pressure by 1 cm every 5 minutes. But maybe this would be too fast to titrate for flow limitations. Especially flow limitations that do not seem to be flagged by OSCAR/my device. 
-I ordered a pulse oximeter too that I'm hoping will give me some useful data.
-Is it worth trying a soft cervical collar?
-It looks like OSCAR might not be flagging all of my flow limitation events. Is there a way to get it to flag them? It would be helpful to have a quantitative number for this. 

Thanks in advance for any help. See attachments below:
   
   
   

[Deborah K.]

I suggest you copy and repost your thread.  Most of us don't know how to advise you with an ASV.  Maybe label it beginning with "Using ASV.", then follow with the rest of your original title.  I hope you get some help!  

[SarcasticDave94]

From a former ASV user for treating Central Apnea, you're likely not going to be able to address flow limits with the ASV. The algorithm has treatment of the Central Apnea as it's primary goal. This is in opposition to FL.

[donsburg]

Ay or may not be helpful re aerophagia but I have found:

1) it is reduced if I use mouth tape, and specifically fold my lips inwards before applying the tape. I think this helps to hold my jaw up.

2) I am a side and front sleeper. On my front I get little aerophagia, on my side I get loads. So I try to sleep only on my front now.

Good luck

[gpenz]

Thanks all. Deborah, thanks for letting me know. I just updated the title in my reply, but can re-post if that doesn't work.  

Dave, that's interesting. Wouldn't it be possible to reduce flow limitation by increasing minimum pressure support? I'm hoping there is a minimum IPAP that gets rid of FL's. 

Donsburg, thanks for the tips. I'm also using mouth tape as well as the respironics premium chinstrap. 

I'm still wondering if anyone can confirm based on my screenshots that my breathing exhibits flow limitation? If so, this might partially explain why I still have fatigue and insomnia. Let me know what you think about this or if you know of any resources that might help.

[Deborah K.]

You did great by renaming the post. You don't need to change a thing now.

[SarcasticDave94]

There are some FL showing up on the chart, but they are very intermittent. And again I think it'll hinder the Central Apnea treatment if you chase after FL reduction. The FL while using an ASV are more likely to be an artifact type of thing.

About the only way to use ASV with low FL is to be contrary like me, with complex Apnea and COPD combined.

[donsburg]

Regarding your flow curves, they look similar to mine, if you search my history I made a thread about it a few months ago. 

We both have a bumpy line towards the end of exhalation. This could be cardiogenic oscillations (aka cardioballistic artefacts - basically your heartbeat gets picked up on the flow curves) OR some sort of expiratory flow limitation. You can try counting the oscillation peaks to see if they line up roughly with your resting heart rate, but I found this somewhat inconclusive.

The question then on the inspiration section of the flow curves is: is the 'double peak' caused by flow limitation, or is it just a continuation of our heart beat being picked up by the sensor? 

I have not found a satisfactory answer and have given up seeking one out for now, focussing on getting my setup (masks, humidifier etc) optimised. One useful thing was that I showed my curves (looking a bit worse than yours) to a helpful person from my sleep study team and she said she thought they looked fine. Which could be a) correct, or b) classic example of sleep tech not knowing things, depending on who you ask !

I spent a while reading the scientific literature about flow limitations and concluded that if what we have is indeed FL then it is at least relatively minor. Your curves for example do have a slight flat top or double peak shape, but the "big picture" of the curve is that it is relatively large and round ish. 

Here is an example of a more serious flattening:

https://publications.ersnet.org/highwire...ext/652611

Full article here: https://publications.ersnet.org/content/...00031-2015

It's frustrating not to be able to answer this more clearly. I have had unexplained chronic fatigue for 6.5 years, recently discovered I have apnea (ahi 19) and CPAP has helped a bit. But I'm left wondering if I have some untreated flow limitations, and whether treating them would help my fatigue symptoms further. I bought a bilevel machine but have not yet experimented with it. My hope is that I might be able to use the settings to improve the roundness of my flow curves

[DaveSkvn]

Hi Gpenz,

Your situation sounds familiar. I was diagnosed with OSA in 2006 (Aged 34, BMI 22) and started CPAP, It helped but I continued to wake in the middle of the night, often lying awake for hours, finally woke early and then continued to "fall asleep" during the day. The old "residual daytime sleepiness" which seems to afflict about a third of CPAP users.

Unfortunately I can't give you many answers. My personal view is that I, and possibly you, have some syndrome that doesn't yet have a name. My apnea is REM related. In the original lab sleep study during NREM sleep the AHI was 4. During REM sleep the AHI was 60. Overall it was about 16. Do you have a REM / NREM breakdown of AHI?

You say you "exercise daily". Back when I was diagnosed, and a couple of years after, I did Olympic distance triathlons in a very amateur way. I always slept worse after a long session. When I woke up randomly at 4am, I'd be awake for 2 hours panicking that I'd not have enough sleep when the alarm went off. I'd be very sleepy the next day and to an extent the day after. Without the exercise, I could get back to sleep much quicker. It got to the stage where I banned myself from swimming, running or cycling. Anything that goes above the aerobic threshold (I think it may increases REM sleep which triggers my problem). I limit myself to walking and light weights these days. You might want to see what happens if you cut down on the exercise for a few days.

My current coping mechanism is to plan for a "midday nap" and then move that nap as early as possible. One alarm goes early at 7am. I have breakfast, do an hour of light weights (to tire me out a bit) and a shower an then return to bed at 9am for a scheduled top up sleep. When the second alarm goes off, about 10.30 am, I'm ready for my day and don't generally fall asleep again. (I have to try moving the 7am back a bit but I'll wait till its a bit warmer.) You might want to give a "false start" a try.

For the record, I had the original (private) sleep study in 2006, a second NHS sleep study (with CPAP on) in 2012 and a third NHS sleep study (with CPAP on) in 2015. The last two found nothing actionable (being NHS you get no paperwork / detail). I've seen three separate sleep consultants (i.e. attending physician in US) in various places. I did set up an infrared webcam and filmed myself sleeping in my own bed for a few weeks at the same time as using a recording oximeter. I put the footage through motion detection software. It showed I was awake pretty much every 45 minutes. After 4 hours it was just a unpredictable mess. The oximeter showed no notable desaturations (i.e. the waking-from-sleep issue is not really apnea). It did show up PLMS but that's not seen as something with a specific treatment in the UK and is just put down to the apnea.

The consultants in the UK have kind of run out of treatment options in my case. ("I have also stopped using my MAD since it caused jaw pain and bite issues." - yep, been there!) I did try Modafinil / Provigil but it had no effect after a couple of months. I was given a trial of Sunosi and it seemed to kept me awake (but not alert or focused) including when trying to sleep at night.

Let me know if any of this rings a bell with you.

[gpenz]

SarcasticDave94, I'm not too worried about centrals, since I didn't have any on my sleep studies. I was also wondering about the FL being an artifact of ASV, but I found this statement in the wiki that leads me to believe my FL's may be upper-airway resistance rather than ASV artifacts: 

"The check for whether flow limitation is upper airway or a result of ventilation is to look at pressure support when it occurs. If the flow limitation mostly occurs during higher pressure support, it is pulmonary. If the flow limitation occurs during minimum or low pressure support, it may be upper respiratory, and a higher minimum pressure support or higher minimum EPAP may help."

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Donsburg, that's interesting about the cardiogenic oscillations. I think that's probably what it is based on looking at my pulse rate, which is around 60bpm, and these bumps are ~1 per second. Even if it were expiratory flow limitation, I'm not sure if that's something I need to be concerned about (though I haven't heard much about it). 

I think it's more likely that the 'double peak' is flow limitation. If it were a continuation of heart beat I think the pattern would be more irregular/random since the heart beats probably don't need to align with breathing. Another reason I think it's flow limitation is because it looks like these 'double peaks' appear to be reduced when my pressure support is higher (I'd like to analyze this more rigorously, but for now just eyeballing it). I'm leaning towards that being option b and the sleep tech not knowing things! 

I took a look at one of your posts, and your flow curve does look a little more flow limited than mine. But we should keep in mind that everyone reacts differently, so a certain degree of flow limitations might cause arousals and fatigue for one person, arousals and no fatigue for another person, or no arousals and no fatigue for another person... One thing you could try is to get a pulse oximeter and see if you have pulse spikes and/or movement and/or O2 desats coinciding with your FL's. I just got myself a Wellue O2ring and the data is pretty interesting.

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DaveSkvn, it's a tough situation. I think it's possible in your and my situations that PAP is not sufficient to treat our sleep-disordered breathing. My AHI is also worse in REM (about double), though in my sleep study I only had 15 minutes of REM so the breakdown isn't too reliable. I think Dr. Soroush Zaghi, Dr. Steven Park, Dr. Anil Rama, and others have said that some people get better results from surgery than from CPAP. Personally I'm looking into getting surgery, since I think it might be more effective. 

I've also found that too much exercise can be a bad thing, so try to limit myself, but also feel like I need exercise in order to feel good, so tend to overdo it regularly. 

It sounds like you have more sleepiness than me right now. I think I have more fatigue and difficulty concentrating rather than sleepiness. 

If you haven't tried increasing your pressure, that might be something to look into, since a lot of people here have had some success with that. Another thing I've been working on is eating clean & nutrition which has been helpful.