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Change in flow rate - what's going on?
#1
Change in flow rate - what's going on?
I've noticed the last few nights I've slept a long time but my flowrate has a sawtooth pattern almost the whole night and I am waking up groggy.

The image attachment shows 3 nights, starting with a better looking night May 3rd, then to worse ones the 24th and 28th of May.  The attachment shows flow rate zoomed back, and then towards the bottom zoomed in where you can see the individual curves. This sawtooth pattern has been going on for weeks now.

http://www.apneaboard.com/wiki/index.php...imitations shows this may be expiratory snoring?  I'm using the Philips DreamWear nasal mask and tape my mouth shut.  That is my setup for all of the above charts.  

Not sure what to do or if this sawtooth pattern is ultimately my problem?  Any advice would be very much appreciated.


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#2
RE: Change in flow rate - what's going on?
I see you have several scales for the flow rate.  It'd be good to stick with one, and I'd suggest making it something like -40 to + 40, to provide better detail.  Use the override feature that you'll see when you right-click on the label for the flow rate graph.

I think you have cardioballistic artifacts showing between breaths; basically, your heartbeat slightly affects the flow rate when you're at zero.  This is nothing to worry about at all; I have the same thing, and I've learned it's not uncommon.  Sometimes the oscillations can be read as little inhalations/exhalations, which artificially inflates the respiration rate, as can be seen on your second and third charts.

I'm also seeing flow limitation.  The visuals in flow rates are an inhalation curve that has dents in the top, a peak, or a plateau, rather than a nice smooth curve.  Not all flow limitations are flagged via the ResMed algorithms.

Can you think of anything that might have increased flow limitations at some point during May?  Possible culprits include nasal congestion and a change in sleep position or posture, perhaps along with a different pillow.
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#3
RE: Change in flow rate - what's going on?
Thank you for the reply Dormeo! I'd never heard of cardiobalistic events. I actually was on an antibiotic over the last week and had been not feeling well a week or so before that, I think I had a mild sinus infection (I had a lot of sinus infections before finally getting deviated septum surgery and sinoplasty last year). I finished up the antibiotic on the 27th but still don't feel 100%. I do feel like antibiotics and not feeling well in general tend to give me a stronger pulse, so perhaps that is showing up.

As for "dents in the top, a peak, or a plateau, rather than a nice smooth curve" I feel like this is probably my issue. I think the majority of my curves show dents at the top, a sharp peak, or (probably most often) a flat plateau. I went from a Philips Dreamstation to a ResMed AirSense when it was suggested the EPR could help with this (but it doesn't seem to have). My waveforms (at best) always seem to have the look of the "expiratory mouth breathing with normal inspiratory flow" (from the flow limitation chart). The long flat line with an eventual plateaued curve.

I've tried different masks, changing the min and max flow, switching machines, and setting a consistent pressure. I sort of feel like even though my AHI looks good that my sleep still isn't particularly refreshing for me. Just not sure what else to try.
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#4
RE: Change in flow rate - what's going on?
I'm not really seeing expiratory mouth breathing in your zoomed views. Mouth breathing would also show up in your leak graph, I think. Plus your mouth would feel like a desert. Sometimes we just have longer pauses between breaths. (In that respect, the "normal" flow rate in the wiki is maybe not so normal -- no pauses.)

The sinus infection may have boosted your flow limitations. With luck, they'll go back down as the infection clears up all the way.

Flow limitations are not a bother at all for many people, but for others they disrupt sleep cycles. I bought myself a ResMed VAuto so I could try a larger difference between inhale pressure and exhale pressure. (On the VAuto, that's called pressure support, and you add PS to your exhale pressure instead of subtracting from your inhale pressure, as with EPR. Just a terminological thing.) My pressure support is 4.8 over an exhale pressure of 5, which I keep fixed. So when I inhale, the pressure rises from 5 to 9.8, and that boost overcomes a lot of flow limitation. Not all, but I stay away from higher PS because it tends to wash out too much CO2 and I get a lot of disruptive central apneas.

Do I sleep better? Hard to say; there are several reasons for my difficulty in sleeping soundly, especially pain. But I do like knowing I've done something about a possible cause within my control.

But that is getting way ahead of the game. When you're completely over the sinus infection, post another chart so we can see what's going on. It would be helpful if you would simply post screenshots of the whole chart, even when you're zooming in. Much easier to read, at least in my browser. And remember to turn off the calendar so more of the left panel is visible.
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#5
RE: Change in flow rate - what's going on?
You'll find a detailed explanation in http://www.apneaboard.com/forums/Thread-...#pid390827
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#6
RE: Change in flow rate - what's going on?
Sinus issues are all clear now.  I tried setting my machine at a min pressure of 14 last night, and honestly, it looks like I just made things worse.  I adjusted the top and bottom of the flow rate chart so it can be seen better.

The image below shows last night at a min pressure of 14, then the flow rate earlier in the night when it actually looked good (shortly after falling asleep), and then the bottom is from December when my pressure was fixed on 7.2 and it seems to look a lot better (though my AHI number was around 2...higher than last nights .71)

I'm thinking of tonight testing the fixed 7.2 pressure again, and if that doesn't work trying a full face mask and trying higher and lower pressures.


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#7
RE: Change in flow rate - what's going on?
The first original example is cardiogenic oscillations. The next two (especially middle one) amplitudes appear to be too large to be only cardiogenic oscillations and this last example is obviously more then cardiogenic oscillations.

There have been a couple members post this sort of waveform. I believe it is asynchronous breathing (breathing muscles acting out of time causing odd flow rate).

One of these members successfully improved his by finding better settings to treat his flow limitation/apnea.

Did you see this same issue when using lower pressure? Your waveforms from 7.2 cm pressure look to be your best.

Of the examples you posted yours appears to be worse at higher pressures, the one tricky thing when interpreting this is to look at average pressure instead of min pressure. For example the middle example your min pressure was the lowest (8.6) but median pressure was the highest (11). Higher pressure does make it harder to exhale which might be worsening/causing this phenomenon.

I don't know what has driven your decision to increase pressure but I don't see apnea as being an issue so assume you may have been attempting to treat flow limitations or maybe the odd hypopneas. Note that not all flow limitations improve with pressure and in some cases I do believe it makes them worse (and always makes it harder to exhale). I would consider trying a fixed lower pressure to see what that does to your results, something like 7 or 8 cm CPAP mode with same 3 EPR.
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#8
RE: Change in flow rate - what's going on?
You're spot on.  My apneas weren't bad on my sleep study (I think 5 per hour on my side and 15 on my back), but I was unable to breathe at night for a long time due to a deviated septum and enlarged turbinates so I think cpap has been targeted more at flow limitation and hypopneas.  

I didn't seem to experience this type of waveform until trying higher pressures.  I'm going to do exactly what you suggested and try a lower pressure tonight and see how that works (with the same EPR).  It seems like the higher pressures may simply be too much.  Thank you very much for your insights!  I'd be curious to see the other thread you mentioned with people with similar waveforms.
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#9
RE: Change in flow rate - what's going on?
Any season allergies in your area?

High pollen count in my area
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#10
RE: Change in flow rate - what's going on?
This is the recent thread that increasing EPR (and therefore ability to exhale) appeared to improve this situation for another poster.

http://www.apneaboard.com/forums/Thread-...ynchronous

Actually I see both of the threads I was aware of appear to have improved this with increasing flow. I didn't remember seeing the response to this thread previously but this member eventually saw improvement when stepping up to a bilevel (Resmed Vauto) and his breathing had significant asynchronicity (imo). You can see one example of where I had this one night as well.

http://www.apneaboard.com/forums/Thread-...ynchronous

Definitely seems that this can be related to flow restriction. Unfortunately since you already are using EPR of 3 there isn't much more you can do with this machine other than reducing pressure to see if that remedies the situation. It would be hard to convince a doctor to step up to bilevel/vauto for this application so only option to go that route would probably be out of pocket used market, hopefully limiting pressure gets good enough results. I had to limit pressure for my grandfather because his flow limitations were driving pressure up making him unable to breath, I've seen enough example now to make me realize that as low of pressure possible is usually best. If ever unsure if a higher pressure is helping my recommendation is to return to a lower pressure, the results need to be obvious for it to be warranted imo.
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