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Desaturating. Fixed pressure CPAP. Strategies?
#1
Desaturating. Fixed pressure CPAP. Strategies?
First, my previous queries were about leaks, which I think I have made good progress with, so I have started a separate thread.  This issue of desaturation occurs whether I have leaks or not.

I have an O2Ring that shows that I desaturate three to four times every night.  Previous sleep studies show that this is generally during REM sleep, possibly starting just before REM.  The lowest that I have seen in 74% though 80 to 85% is more typical as the low.  My running average is currently in the range of 10 minutes total below 90%. 

I am on a fixed pressure of 9 cmH20.  The titration sleep study recommended 11 cm but I have been on 9 cm since I bought my own machine in March 2018.  I presume the equipment supplier adjusted the pressure down while I was still renting as a trial.  I have played with the pressure just recently in relation to leaks, but have come back to 9 cm for now.  Since I run a constant pressure, I have not included this chart in the attached screenshots.

My EPR is on, set to 3.  I had a DS1 until last month which had CFlex+ set to 1.  When I was given the AS10 in its place, the equipment supplier set EPR to 3.  When I saw that, I tested different EPR settings but found that the machine showed Cheyne Stokes Respiration when EPR was off and that my flow limits, seen in the summary chart, were noticeably higher with EPR < 3.

My snore is hardly ever reported as anything above zero, so I have not included that chart either.

I very seldom have any OA events. Some CA events but mostly hypopneas - and those are mostly during the desaturations.  Overall, my AHI is consistently low - typically reported to be less than 2 on the AS10, less than 1 on the DS1.  Consequently, my respiratory specialist keeps telling me that all is good.  He's wrong, I wake up every day with a headache, fatigue, brain fog, aching muscles, sore joints and, recently, numb toes.


I have been using an Eson 2 nasal mask.  I tried an F30 for a week, which helped with leaks, but have returned to the Eson 2 without having leaks reoccur.  Possibly the desaturations were not quite as low with the FFM, but some were so it is difficult to really say.  I have been using a soft cervical collar.

Oh, I have lost a bit more than 20 kg (about 50 lbs) since Easter.  I plan to keep going to lose a bit more but I am close to a reasonable weight.

What I notice from the charts in OSACR is that I will be sleeping well, with a consistent respiratory rate, but that my tidal volume appears to decrease over a period of time for no obvious reason and with no impact on SpO2.  Then, sometimes but not normally preceded by a CA, the SpO2 drops quite rapidly and I start into a cycle of periodic breathing and desaturation.  My thinking is that perhaps my pressure is too high, I am hyperventilating, my CO2 drops as a result and that causes the reduction in tidal volume.  At some point, SpO2 drops quite rapidly, which causes an arousal, an increase in tidal volume and SpO2.  Then that the cycle repeats for a period of time.  Does that sound likely?

I do understand that I may need a different type of machine to fix this.  I have a sleep study booked just before Christmas and the lab has me flagged to be monitored by a senior tech.  What I am trying to work out, however, is whether there is anything that I can do / test before then.  I am thinking of dropping my pressure to 8 for a few nights and then to 7 providing I do not get OAs.  I am also wondering if it is worth exploring whether a FFM does make a difference. 

Sorry for the long write-up and thanks for the input.


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#2
RE: Desaturating. Fixed pressure CPAP. Strategies?
Oh, oops.

I have just realised that the time synchronisation between the CPAP and O2Ring was not so great in the charts that I attached.  My CPAP had been unplugged for the day so the clock went off at its own pace.  As best as I could work out, the SpO2 and pulse rate charts lag the CPAP charts by about 30 seconds. 

Sorry, I will look for some other charts tomorrow if necessary.
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#3
RE: Desaturating. Fixed pressure CPAP. Strategies?
StuartC - Delete the O2Ring data for that day.  Now, take note of your CPAP starting time.   Rename your oximeter data file name to match the starting time.   You need to only modify the last 6 digits to 002135.  Reimport the renamed file and it should match.
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#4
RE: Desaturating. Fixed pressure CPAP. Strategies?
I'd also be interested in seeing the "Advanced" graphs. Just go to the Oscar menu View and reset graphs to Advance and take the screenshot. This will show us your minute vent which will show us the changes in your respiratory volume.
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#5
RE: Desaturating. Fixed pressure CPAP. Strategies?
(11-20-2021, 09:10 AM)Sleeprider Wrote: I'd also be interested in seeing the "Advanced" graphs.  Just go to the Oscar menu View and reset graphs to Advance and take the screenshot.  This will show us your minute vent which will show us the changes in your respiratory volume.

Yes, I would be interested in seeing them too.  Unfortunately, I do not get them from the AS10 in daily view, only as summary data in the overview charts.  I used to get them from the DS1, but have no SpO2 graphs to match.  I might be able to dig through some of that data to see if there is anything visible there, but I will be manually inferring when I had desaturations based on what I have learned about my flow rate graphs.

Instead I did it the old-fashioned way - by eye.  Once, before I had my butt handed to me by whatever medical mysteries currently rule my life, I was a Control Systems Engineer.  I have also drawn a few trend lines on stock price charts.  So, I've had a bit of practice.  I have attached two example charts from a different night (9 November) to my original charts where the trends are a little clearer for each of the three desats that night.  The expanded chart is noisy but makes the angles of the trends more apparent.  Ironically, however, I find these easier to see in the more compressed of the two charts.

As I looked for a good example to show you, I realised that the trend that I see and described perhaps is not happening quite so clearly every time.  But sometimes it is a real ripper, look at the second desat in the third chart attached (18 November).


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#6
RE: Desaturating. Fixed pressure CPAP. Strategies?
The daily detail view will give you the standard and advanced views. The advanced view lets us see the chart below with mask pressure, tidal volume, minute vent and inspiration time, and is obtained by using the view menu command I described earlier.  View/Reset Graphs/Advanced.

[Image: attachment.php?aid=37312]


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Sleeprider
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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#7
RE: Desaturating. Fixed pressure CPAP. Strategies?
Yes, I have changed the Daily view as per your instructions.  The charts are simply not there.  I have no idea why.  I will pm you with an unlisted YouTube link so you can see what I see.

However, I did go back into the DS1 data and have something to show you.  I have annotated the 10 minute chart with values and the likely desat period.  The point of the red circles is to note that the flow rate is higher between cycles then than what I see now with the AS10.  Perhaps that is why I have the perception that I feel worse since getting the AS10.


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#8
RE: Desaturating. Fixed pressure CPAP. Strategies?
I see a lot of flow limits on the PR closeup, assuming this is at least somewhat consistent you have a problem with flow limits. Your RERAS back this up. The flow limits will be much more evident in a 3 minute view instead of the 11 minute view.
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#9
RE: Desaturating. Fixed pressure CPAP. Strategies?
(11-20-2021, 08:13 PM)Gideon Wrote: I see a lot of flow limits on the PR closeup, assuming this is at least somewhat consistent you have a problem with flow limits.  Your RERAS back this up.  The flow limits will be much more evident in a 3 minute view instead of the 11 minute view.

I have done some work around leaks and the resulting flow limits.  I think I am better now than when I started with the AS10 six weeks ago, and almost surely better than the DS1 chart from May.  Is this perhaps something you would agree with based on the more recent charts from the AS1?

By "better", I mean that the more significant flow limits that I have now occur mostly during the desaturations.  It makes sense to me that one is likely to be causing the other, but I do not know which way round.  If my initial description of what I think is happening is correct then I think the desaturations are causing flow limits but that is the point of asking questions here. 

Of course, the AS10 does not report RERAs the way the DS1 did.  What I do have, complements of the O2Ring, are pulse rate changes.  They are easy to explain when they follow a change or disturbance in flow rate or leak rate but they are less easy to explain if they do not.  Regardless, I have been wondering if they are my new equivalent indicator of issues to what RERAs were on the DS1.

Thanks
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#10
RE: Desaturating. Fixed pressure CPAP. Strategies?
IMHO DeSats are the result, not the cause.
I know this sounds ridiculous but hold your breath, the accompanying DeSat cause you to hold your breath?
Yes, DeSats may very well be an indicator of where to look for you.
The purpose of the 3 minute View is to provide more clarity on your flow limits.
If you are having DeSats before your flow limits I would question the synching of your SPO2 on with OSCAR.
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