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[CPAP] Help Interpreting Data / Graph
#1
Hi everyone, 

I'm new to this board, but have been using a CPAP for ~3 years now. Using a phillips respironics system one at 7cm fixed pressure. 

I still don't feel 100% though, and can easily sleep 9-10 hours on most days. So lately, I've been trying to understand my sleepyhead graphs better so I can adjust the therapy. 

Now this graph -- ibb.co/gTQL8a -- can you help me understand the hypopnea event #1 ? The H event following it looks more normal, but that first one.. 

ibb.co/gTQL8a

Why is the flow rate flat during exhalation (or in the middle of exhalation..?) It looks like I was holding my breath for 15 seconds (3:11:30 -- 3:11:45) 

I get this often in the flow rate graph. It doesn't look like it's due to leaks, since there's no spike in the leak rate. Or is there, I can't tell. The tidal volume goes way up, so it has to be a leak yes?

Thanks for any and all help on this, really appreciate it! 

Daniel
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#2
You pegged the inhale flow rate for about three seconds! I don't think your lungs can do that. But leak detection relies on a more steady increase in flow rate, using digital filtering of the flow rate signal, so that spike won't show up as a leak. Nevertheless, I'm pretty sure you had a two or three second leak. You appear to have a Respironics machine, so I can't exactly duplicate, but I might try. Much depends on the machine's leak detection algorithm.
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#3
Here's a link that will help you out in the future. It's called "Beginner's Guide to SleepyHead. http://www.apneaboard.com/wiki/index.php...SleepyHead
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#4
To me, and I don't know, it looks like this event could be a hicup.
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#5
Hi dcg494,
WELCOME! to the forum.!
Hang in there for more assistance with your graphs, good luck with CPAP therapy.
trish6hundred
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#6
Hi Pholynyk, thanks for the help on this. You’re right it does seem to take 3 seconds for one inhale, what do you mean by ‘pegged the inhale flow rate’ though ? Can I actually set this on the machine ? I always figured the cpap detects my flow rate and adjusts automatically.

Indeed, I have a respironics machine. I tried duplicating this last night, but it looked a bit different and it didn’t show up as a hypopnea event. 

You'll see the leak graph does have a slight upward slope immediately following the spike, so it should be a leak. However, that would mean many of my H events each night are simply leaks, not actual events. Is it normal that the machine would flag such leaks as hypopnea events ?
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#7
You hit the top of the chart for about three seconds - it went "off the scale", the needle on the old-fashioned analogue meter hit the peg on the right hand side of the meter that keeps the needle from hitting the side of the meter. In audio terms, the signal is getting clipped at 130 litres per minute.
You can adjust the scales on the graphs, by right-clicking just outside the graph area on the left side. On the other hand, the actual flow sensor does have a maximum rate it can measure, and we don't know what that is. As well, the 'flow generator' (turbine fan) has a maximum speed which sets the maximum flow available, It probably is about 130 to 150 litres per minute.
As I look at the leak rate, I see it rising gradually from the left end, peaking sometime after the big leak, and then returning to its earlier value. Remember I said that the leak rate is a calculated value, based on averaging out your inhales and exhales using some digital filtering algorithm. I like to think of our breathing as an alternating signal sitting on top of the steady(ish) venting plus leakage, much like an audio signal with a DC voltage offset.

I hope that makes sense to you. I ought to be asleep at this hour, so I can't guarantee that.
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#8
Great, thanks a lot P! That's really helpful.

Why does the CPAP counts this as a hypopnea event, it's a leak, you'd think they would have built this into the algorithm.
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