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New user here, I have been lurking for a few months learning as much as I can and using OSCAR / sleep hq. This forum has been unbelievably helpful so far, thank you to everyone!
Quick background:
Diagnosed Moderate OSA in May 2024 (AHI = 19). Started APAP June 2024.
Immediately getting AHI = ~1, and I think it's helping me feel better in the day too.
However I'm not feeling fully better.
I noticed a couple of aspects of my flow curves which seem unusual, and perhaps worth investigating.
----------------------------------------------------------------------------------------------------------------------------------------- 1. The flow curve between expiration and inspiration often appears ragged. There are also Flow Limitation indications on the peaks of the curve (double peaks, irregular peaks etc.). [Image 1]
2. There are common sections where my breathing takes on a sinusoidal shape. A bit like a very mild Cheyne-Stokes pattern. [Image 2]
3. My tidal volume appears to be on the low side, last month median = 400ml.
From my limited research I suspect 2. and 3. might be completely normal?
I'm mostly curious about 1. Is it:
normal?
something to do with the machines Forced Oscillation Technique? (I think not because when I have a CA the FOT amplitude is much larger than what I've highlighted here)
an indication of Sleep Disordered Breathing of some kind? Flow Limitation? And if so, how best to treat it?
Any comments and thoughts gratefully received. I've attached my initial sleep study in case it is of interest.
I should add - I’m about to purchase a Prisma 20A (chosen because it has a slightly larger Pressure Support than Resmed EPR - 4cmH2O vs 3). However, if it seems likely that these flow limitations may need a bilevel device, please let me know so I can consider whether it makes sense to try/purchase a bilevel instead.
Here is a representative image of my flow limitation graph for a whole night. My 95% FL number is 0.03 over the last month, so I think that is good. Maybe I’m focussing too much on the nature of the flow curves. They just look wrong compared to others I’ve seen which are smooth and rounded!
Dormeo kindly helped me with the answer to question 1 in another thread, it is cardioballistic artifact, and not a problem. Phew!
So really my main concern now is: are the flow limitations I'm seeing enough to warrant trying a bilevel machine, or should I be ok with the Prisma 20A and its roughly 4 cmH2O of pressure support available?
If you want to try greater pressure support, you could opt for a ResMed Aircurve 10 VAuto.
Some people are not sensitive to flow limitations at all; others are. It's unfortunately impossible to know in advance whether addressing FLs with greater PS would help you feel more rested.
Complicating things a little: I looked again at that zoomed-in view, and it's *conceivable* that you're seeing cardioballistic artifacts in some of your inhalation and exhalation traces. That's a bit unusual, but I think I've seen experienced people here say it's possible.
If I were in your place, I'd concentrate for now on getting 7.5 to 8 hours per night of actual sleep -- not just time in bed or time on the machine. Is that something you can do?
Thank you Dormeo. So are you saying that (maybe) what looks like a mini single or double peak - on the top of the main inspiration peak - could be caused by the same cardio ballistic mechanism as on the expiration section of the curve? I do see what you mean when I look at it.
I would just go for a bilevel device, but they seem to be about double the cost so I'm trying to work out in advance if it is likely to be helpful. Or at least see if I can rule out needing it.
My plan for now (I have the rental airsense 10 for another 10 days) is to increase my min pressure a little, keep epr on 3, and see if that reduces the flow limitations.
I do actually manage around 7-7.5 hrs with the machine most nights by the way, the examples posted are not representative.
Thanks for the link; that was helpful. Yes, I was wondering whether some of the dents in the flow-rate traces were also CB artifacts. But if they are, they show up only infrequently. I'm now pretty skeptical that's what's going on.
Your FL data are good, though it's true that the machine flags some FLs and not others. FLs of the kind you're seeing won't both a lot of people, though it's true they might bother some. There's a lot of chanciness about focusing on FLs.
But yes, try inching your pressure up a little to see what happens in the remaining time you have with your current machine.
If you wind up weighing the Lowenstein machine vs the VAuto, bear in mind that you can always get some of your money back by selling either machine used. Ideally you'd have a chance to rent one or both before making a choice. Some people love their Prismas and others don't:
It's good to see you usually get more time on the machine than 4 hours, though as far as actual sleep time goes, I suspect you're usually barely getting 7 hours. You might like what 8 hours can do for you.
Ok so I bumped my minimum pressure from 7.6 up to 8.4 for two nights and again to 8.8 last night. I didn't notice any difference and slept the same. The flow curves from all three days remained similar to before, with a lot of cardioballistic artefacts through much of the night. FL statistics remained similar.
I will try and bump the pressure up further.
I'm still thinking about whether what appears to be single / double peak flow limitations (on the main inspiration peak of the flow curve) are indeed flow limitations, or are in fact a continuation of the cardioballistic artefacts. A couple of examples from last night:
With FL-looking peaks to the inspiration curve:
With normal-looking peaks to the inspiration curve:
Raising your pressure is a reasonable experiment given the options you have. But EPR/PS is the best tool for addressing FLs, as you know. The little push in pressure upon inhalation helps overcome slight limitations in the pharynx.
As for the CB artifact theory -- we'll never really know. Certainly you have normal-looking flow-rate traces during other intervals.
