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AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks?
#1
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AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks?
I believe members can collaborate in this thread to assess and deal more effectively with this subject's breathing disturbances now given that much of the necessary information is only two mouse drags away.  There is a ResMed patent signal (just below) that machine-algorithm help may be forthcoming within the next generation or two of their xPAP machines. 

This thread is not a call for my personal treatment help (though it will show my workups of OSCAR graphs, those crude things being all I have for illustrations and questions here). I will start or use a previous thread for my treatment related questions. 

Please contribute to here as our learning space if the thread subject applies to your sleep with low AHI. Contribute if you have questions, corrections, a different interpretation or have other information to share about feeling or being treated for unrestul sleep.

1. I've seen, as Pubmed indicates (2020),  our machines produce and do show untapped information though it is not machine flagged for OSCAR graphs that presently show that information (in the flow rate (FR) curve deformations). We can jointly try to devise a manual method  for seeing and using OSCAR's present display of that information now, while hoping next generation machines will exploit that information to help our sleep. See https://pubmed.ncbi.nlm.nih.gov/32289733/

Each of us must decide how important fixing our sleep is. "Improve your sleep hygiene" is the usual, good recommendation. But at advanced age, one's  remaining pleasures after treatment and reforms can be hard to drop.  Compelling focused evidence from a reasonable trial period of change would sell me. Such evidence would also scratch my continuing itch to learn more about this complex, interesting topic.

2. Dr Park explains detrimental effects of spontaneous and other arousals that cause sleep fragmentation:
https://doctorstevenpark.com/spontaneous...e%20night.

3. Importance of measures and scoring of flow limits (FL) was the focus of a 2017 medical conference: https://www.atsjournals.org/doi/pdf/10.1...1704-318WS

4. Medical (and machine marketing?) importance of metrics, detections and flagging of flow-limit caused deformations of inspiratory flow rate peaks was recognized in the linked 2018 Resmed patent application: https://patentimages.storage.googleapis....2088A1.pdf

What is the problem and what gives rise to it? 

5.  Mainly, it is the Biomechanics of the upper airway. A floppy tube?
https://journals.physiology.org/doi/full...00539.2013

6.  UARS and  RERA definitions are clearly explained: 
https://sleepapneamatters.com/apnea-vs-h...a-vs-rera/

7.  Nature of arousal in sleep, sleep disruptors:
http://www.sciencesleep.org/ziliao/The%2...0sleep.pdf

8. Microarousals. More Sleep disruptors: 
https://onlinelibrary.wiley.com/doi/pdf/...97.00276.x

9. How can we see our flow rate (FR) curve irregularities are causing or contributing to our arousals and micro arousals. Explained here there are 47 classes of normal or more deformed inspiratory FR peaks having 3 levels of severity: normal, moderate and severe:
https://www.hindawi.com/journals/cmmm/2017/2750701/ (Seven broad classes of shape were documented in 2001 by Tero Aittokallio, et al. in Finland, as noted below.)

How does  this and related information fit into information of the kind sensed and compiled in sleep laboratories' reports.

10. Here are two sets of curves. First, the "A" set which summarizes (in a set of 7 synchronized graphs) how the various PSG metrics (EEG, EMG, Pes, Flow, Ventilation and SpO2) all fit together and illustrates how the arousal threshold (ArTH) was "backed into" (with reverse-engineering calculations) to determine (estimate?) and graph the ArTH. OSA sufferers, as shown in "A" have a higher ArTH than UARS and FL affected patients. The patient's ventilatory drive has to reach a higher level to open the obstructed airway. Second, is the "B" set of curves for the low ArTH patient having UARS and FL who tends to awaken (arouse) more easily than the OSA sufferer. Note that the indicated gold standard for determining ArTH is the sleep lab's EMG (diaphragm muscle action measurement) and Pes (esophageal pressure). The A and B curves, showing ventilatory drive, necessarily used the gold standard EMG and Pes curves (standards) and data as baselines to back into the ArTH level. But the graphs include the corresponding EEG power.
https://www.ncbi.nlm.nih.gov/pmc/article...figure/F1/

11. Here is the research abstract of research underlying the A and B sets of graphs in the item above. 
https://pubmed.ncbi.nlm.nih.gov/29228393/

Among other related and significant matters:

12. What level of FL is normal? Indications are that the "cut point" distinguishing Normal from troubled sleepers, is having an AHI<=5 with no more than 30% FL:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3792383/

13. An indication the AutoSet (AirSense AutoSet?) can help identify arousals:
https://pubmed.ncbi.nlm.nih.gov/9817142/

14. A survey reporting about literature on UARS topics:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4608900/

15. Early research determining 7 flow rate shapes by Tero Aittokallia et al. of Finland, a bio-mathematician, I believe.
https://pdfs.semanticscholar.org/0c30/43...370be1.pdf

16. Some explanation of brain waves detected and measured in sleep and wakefulness: https://psych.athabascau.ca/html/Psych28...ness.shtml

17. Information about ArTH and related stimuli: https://pubmed.ncbi.nlm.nih.gov/9351134/

18. How low adherence or compliance can stem from low ArTH. PAP not or not seeming to help arousals and sleep fragmentation for UARS, etc.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5940420/

19. Apparently there is a cognitive link between awake arousability and sleep-disturbing arousability.
https://www.sciencedirect.com/science/ar...m%20sleep.


I will post related matter from my OSCAR presentations in a later post.

2SB
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#2
RE: AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks?
2SB, you've clearly put some time into this. I am very interested in the topic but will admit I'm not likely to immerse myself to a similar degree. consequently, I appreciate the broad brush introduction / summary you've presented and encourage you to continue to give us crib note level summaries, your analyses, hypotheses & conclusions (in addition to the citations for those that want to dig in). I don't know that I'll be able to contribute much to the discussion but I will surely be following along.
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#3
RE: AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks?
Physiological consequences of prolonged periods of flow limitation in patients with sleep apnea hypopnea syndrome - Respiratory Medicine

I found this interesting from resmed
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#4
RE: AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks?
Good article with explanations of flow limitation and its impacts. I is surprising to me that they were able to optimize using CPAP alone without bilevel pressure. Article is a little short on details for therapy inputs.
Sleeprider
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#5
RE: AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks?
Thanks 2SleepBetta, very informative, I will continue to read this.

And thank you Zackio! a most timely post and highly relevant to my own experience here.

I hesitated to post this much detail and such a long post, but you have inspired me to share this.
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#6
RE: AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks?
I found this interview very interesting in light of UARS https://doctorstevenpark.com/expert-inte...lt-on-uars

Sleeprider, I thought that too. Problem is even if you could, the pressures required may be very uncomfortable and create it's own problems.
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#7
RE: AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks?
Zackio and SevereSleepApnea,

Great on target and solid contributions to "the cause" from both of you. Lots to digest, re-read, think about, act on and share where appropriate. I read or listened to  it all, learning a lot but needing to spend more thinking time. Thank you for posting and commenting here.

Dr. Guillenmenault clearly explained the progression that begins with mild, untreated (flow limited) SDB and snoring which destroys critical sensors, burns our "recovery bridges" behind us. We eventually reach endpoints/waypoints in Sleep Apnea and various well known and serious comorbidities. My sense is most of us come to treatment and awareness of need along a tortuous, even circular path, often one of denial, with severe irreversible damage done along the way. We complete our circle (with our treated low AHI if OSA was our problem as mine was and is) and still need to  deal with our now lifelong, underlying flow limits of one kind or another (UARS like symptoms at some level); further, we have lost/destroyed/squandered much of the neuromuscular capacity we once had to deal with it. I took that path anyway (multiple heart implants, a level of CAD now) and I would bet SSA would concur--thinking of the hellish medical event he survived during a visit to Italy and is still addressing. 

There's a lot to go back and review from those good UARS-focused sources, but here is one more tidbit from that pioneer sleep researcher, Dr G. that rang a bell for me. He spoke of how early childhood mouth breathing interfered with development of adequate nasal airways. I was a sickly preschool brat that fortunately became a healthy kid and adult--asthma, allergies, seasonal respiratory problems, rheumatic fever--I'd bet all that contributed to becoming a mouth breather then that continues to now--some level of structural nasal airflow restrictions as a consequence of a plugged nose. 

Literally, I thank God, and a good doctor (with SDB) who started me with a home test, after complaints about nocturia (which puzzled me then), and an Rx for and delivery to me of an Autoset. But he then left me to sink or swim. Again, thank God, I soon found, lurked at and called for help at ApneaBoard; soon OSA was well controlled and it is now full circle, "back to dealing now with far fewer FL and lots of unflagged "fl".
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#8
RE: AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks?
Yes, the "progressive destruction" part caught my attention as well. Also what he was saying about the research not making the jump to clinical practice. The sleep techs not being fully trained or given time to fully analyse sleep studies.

There is a progressive nature to uncontrolled asthma too with "airway remodelling". I have read some papers about "overlap syndrome" Creating a worse condition than each alone, they suggested a unique pathophysiology in the paper. For some of us with nasal congestion or other airway problem, it's adding to the puzzle.

https://onlinelibrary.wiley.com/doi/full...resp.13107
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