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Understanding Flow Limitations and Flow Rate Shape
#1
Understanding Flow Limitations and Flow Rate Shape
Hi, I've recently started using an APAP to treat my mild apnea (AHI: 0.7 and RDI: 12.7, From what I understand, these are low numbers, but I have symptoms).

I originally had the APAP set to min:5 and max:15 as that is my prescription. The sleep doctor I'm with isn't doing in-clinic titrations because of the pandemic (partly due to backlog and prioritizing diagnosis and partly because they don't want to be using PAP therapy in their clinic right now), so I've been messing around with settings on my own and have set the pressure settings to min:10 and max:20.

From what I can tell, I have slight flow limitations, as shown below. Also, my flow rate graph has a lot of flat or bimodal inspiration peaks which I've read is also due to flow limitations.

I was wondering how to tell if this is a problem and how to tell whether I should increase the min pressure (beyond just continuing to mess around with settings and see what feels comfortable). Should I increase pressure until almost all of my inspiratory peaks are sinusoidal like they are when I'm awake, or should I just ensure that the flow limitations are below .25 (or some other threshold)?

Thanks for any tips/advice!


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#2
RE: Understanding Flow Limitations and Flow Rate Shape
Welcome to Apnea Board.
I would suggest you include the same OSCAR screenshot, but as a zoomed out chart to show the full night. We need to have an idea of what's happening overall and then we can comment on both these shots of no zoom and the zoomed in. It just helps to get the overall first. Regardless, there is something going on that needs addressed. I will let the pressure/chart gurus chime in, as I'm not great with the charts on breath patterns other than to say there's a flow limit or something going on.
Dave

OSCAR
Standard OSCAR Chart Order
Mask Primer
Dealing With A DME
Soft Cervical Collar Wiki
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEBSITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#3
RE: Understanding Flow Limitations and Flow Rate Shape
Here's the zoomed out data.


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#4
RE: Understanding Flow Limitations and Flow Rate Shape
Not bad overall. I see flow limits exist on a lower level. These may or may not be an issue. How did you feel during and after therapy? Do you feel better for the therapy or are there symptoms that you feel are yet to be addressed? By the numbers only, it doesn't seem too bad except a little bit of FL and the zoomed in flow rate somewhat flat tops. I'd consider symptoms to be your setting change guide more than just numbers, as they are really quite good in this chart.
Dave

OSCAR
Standard OSCAR Chart Order
Mask Primer
Dealing With A DME
Soft Cervical Collar Wiki
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEBSITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#5
RE: Understanding Flow Limitations and Flow Rate Shape
Hello, zzzJ.  The number one question is how you are feeling.  If you're feeling rested during the day and have solid-feeling sleep during the night, then you don't have a problem.  If you are still feeling sleepy during the day, or have the impression you're waking up frequently, then you might have a problem.

I would just say, "Yes, those are flow limitations," except that it is *possible* some of the dented inhalation traces are telegraphing your heartbeat.  The reason I say that is that you clearly have a "cardioballistic artifact" between breaths and (I *think*) sometimes during your exhalation.  It would be unusual for this artifact to show up during inhalation but not impossible.  In fact, on another forum, there's some discussion of whether that's what's going on with the graph attached.  Just to be clear, cardioballistic artifacts are nothing to worry about.  It just means your heartbeat registers in your flow rate.

I'll be curious what the experts have to say about this.


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#6
RE: Understanding Flow Limitations and Flow Rate Shape
I think this could be correct! I have a very strong heart beat, especially when I am lying down relaxed. I think I can slightly see what might be these artifacts while I am still asleep, but it seems to be masked by more full breathes. I'll have to do some experimentation in this regard...

I am still a bit sleepy, but mostly just having a hard time focusing. Last night did seem to be better sleep, but often the fatigue comes in waves, so we'll see.
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#7
RE: Understanding Flow Limitations and Flow Rate Shape
I do read in your first post you started PAP recently. About how long ago? I know for me I didn't feel much different until the first month was past, and then as it was where the difference was a feeling of a bit less tired more than anything else. I did use that first month to get used to PAP therapy by small mask and machine On times while awake to adjust a bit to it. Then I had to make several therapy setting adjustments, basically doing my own titration over that month.

As is, less tired than prior can be a positive sign. To your success Coffee
Dave

OSCAR
Standard OSCAR Chart Order
Mask Primer
Dealing With A DME
Soft Cervical Collar Wiki
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEBSITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#8
RE: Understanding Flow Limitations and Flow Rate Shape
Were these numbers from your diagnostic study?
(AHI: 0.7 and RDI: 12.7)
If so this is implying UARS, Upper Airway Resistance Syndrome. RERA, and UARS, both are heavily involved with flow limits.
The first step is to get you to EPR=3 Full time and you are already there.  
Your heartbeat is showing in your waveform but I'm still seeing significant flow limitations.
Where you are at is pretty much the limit of where we can take you on an AutoSet, and a lot further than we could take you with a DreamStation.


Now we need a critical evaluation of your symptoms, we need to determine if this needs to be pursued further. And we need your opinion on advancing treatment. Most doctors would consider you cured. So in detail, what are your symptoms?
Here is a list, not all inconclusive, of symptoms.
Note that these are not all specific to Central/Mixed/Complex apnea. They are symptoms that impact our sleeping, arousals, and yes apnea too. Think of these, but do not limit yourself to these when you are asked "How do you feel?"

  • Daytime hypersomnolence;

  • Excessive fatigue;

  • Morning headache;

  • Cognitive dysfunction;

  • Dyspnea, etc.;

  • Fatigue;

  • Insomnia;

  • Difficulty going to sleep;

  • Difficulty falling asleep;

  • Wakening during the night;

  • Daytime Sleepiness;

  • Excessive Daytime Sleepiness (EDS);

  • Poor concentration;

  • Difficulty with balance;

  • Shortness of breath;

  • Dry mouth;

  • Restless Sleep;

  • Non-Restorative Sleep;

  • Snoring;

  • Obstructive Sleep Apnea;

  • Restless Leg Syndrome;

  • Nocturnal Leg Cramps;
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter

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#9
RE: Understanding Flow Limitations and Flow Rate Shape
Thanks for all the feedback!

> Were these numbers from your diagnostic study?
> (AHI: 0.7 and RDI: 12.7)

Yep, these were from a WatchPAT (the sleep clinic had really long wait times due to covid, so I've not had an in-lab test). I should also probably note that the RDI was higher in REM (maybe double, but it did look like the WatchPAT miscalculated REM at one point and that I could have an even higher proportion in REM).

> Now we need a critical evaluation of your symptoms, we need to determine if this needs to be pursued further. And we need your opinion on advancing treatment. Most doctors would consider you cured. So in detail, what are your symptoms?

Haha, the first doctor I met with was really reticent to send me to a sleep doctor because I wasn't "old and fat", so it doesn't surprise me that I'd be considered cured by some.

My symptoms include
daytime hypersomnolence and excessive daytime sleepiness (though this isn't constant and was at it's absolute worst 6 to 8 years ago);
fatigue;
cognitive dysfunction and inability to focus;
wakening during the night (mostly in the morning hours, which I think is because more REM);
unrefreshing sleep;
bad bruxism since childhood;
hypoglycemia with exercise, especially after eating (been measured by a continuous glucose monitor, I'm guessing this could be related to my sleep, but who knows);
feel worse after consistent exercise;
never had good balance/coordination, but it's gotten worse and I run into doors/walls a lot more;
heart rate goes up a decent amount just from standing, maybe POTS-like in symptoms but I haven't ever fainted.

Also, and this is a new symptom for me, so it might be a one off thing, but I had a sleep paralysis episode with hallucination for the first time this morning.

I still don't think I'm all good today, but I would think that it would take some time to really notice a difference for some of these symptoms.

As for next steps that I'm considering, I'm hoping that CPAP (or Bilevel if this doesn't end up helping) will be enough to help me feel well and that I could eventually get MMA or some other potentially more permanent treatment. I think my jaw is somewhat recessed and I might have a small nasal airway too.
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#10
RE: Understanding Flow Limitations and Flow Rate Shape
Oh, and it has been only a few nights with CPAP. The first two nights I only ended up sleeping with it for 4 hours and last night was the first time with it for the full time. The first two times I was also trying to use a device I bought off Amazon that pulls your tongue forward but I got a sore under my tongue from it and it is not incredibly comfortable, so I'm not wearing it for a bit. It did seem to keep my tongue out of my throat (when I was laying on my back while awake).
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