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09-01-2016, 04:11 AM
09-01-2016, 04:35 AM
That explanation was brilliant.
I'm going to do some of those plots when I get data with the new settings.
(With my current setting my inverted bell curve would be very one-sided.)
Thanks, I'm changing to 7 - 12 from now.
Thanks both of you!
I'll update those plots in a week or two.
My CA is lower than OA & H so I hope to respond.
I don't think I've wasted time though, its only recently that I've felt under control with the pressure, comfort, leaks etc.
Ready to try new setting now.
Plotting an inverse bell curve manually is not practical ... it takes so much data to see the trend ... basically for a decent time period, something like weeks or months, you'd have to look at all the time spent at a given pressure and determine the overall AHI for all the time at that pressure, then repeat for all pressures. Wish I could find my old screenshots ...
So here is a SH screenshot from earlier this year when I was still on my APAP ...
Sorry, the image attachment doesn't seem to work, or I'm too dumb with my 25 years of IT experience to figure it out lol ....
I have the machine range set to 17-20 cmH2O. I'm only giving it a range of 3 cmH2O to operate in. Pretty tight confines, and actually it could be tightened up more as I'll explain later.
What I want to point out here is the 'Pressure' line on the pressure graph. You'll notice the vast majority of the time I'm at 17 cmH2O. In fact, if you look at the 95% number in the summary, it is 17 cmH2O, which is also my Min pressure. Cruising along at 17 cmH2O is preventing the vast majority of my issues. What you want to work towards is having a graph like this, where your minimum pressure is preventing the vast majority of your issues. This is basically what a straight CPAP will do.
But, in this case, we have the advantage of range that an APAP provides. So again looking at the pressure line, you see it periodically depart the 17 cmH2O pressure and goes up. This is the APAP detecting issues and adjusting the pressure accordingly to try to resolve them. When it feels the issue has been resolved, it will drop back down towards the minimum pressure of 17 cmH2O. This is what all the spikes on the pressure line represent.
You'll notice even though I have the machine set to operate in the 17-20 cmH2O range, this night it only used pressures in the 17cmH2O to 18.5 cmH2O range and resulted in an AHI of 0.61. The peaks never came close to the 20 cmH2O I was allowing it. If I look at other nights earlier this year, this pressure pattern is very typical for me. As I mentioned earlier, the higher a pressure departs (either lower or higher) from your 90%/95% ideal pressure the more potential you have for issues. In this case I want to give the APAP enough space to deal with the odd issue, which it does between 17 cmH2O and 18.5 cmH2O every night for months on end. So, I could reduce the high end of the range down to 19 as it rarely ever gets to 19. It gets to 18.5 on a regular basis to deal with issues not handled by the minimum pressure, so it should just be set to 0.5 cmH2O above it's normal peak to keep it from running away on me to higher pressures, which we know increases AHI and also causes additional mask leaks, both which will reduce your quality of sleep.
Hope this makes some sense.
So, what you want to do to get your machine to the point it is handling your issues as well as my example. To get there you need to:
1. Keep moving your min pressure up until you find the spot where your min pressure is the same as your 95% pressure and
2. Keep adjusting your max pressure (upwards or downwards) to the point where it is barely above (0.5-1.5 cmH2O) above your typical spikes on your pressure graph.
Looking at your two nights of data, your 95% number was 8.7 and 10. 10 was also the high end of your range, so your 95% could have been higher (but I don't think by much) but your machine might have cut you off. Your current minimum is 5 which is way below your 95% zone, your sweet spot. As mentioned previously, generally the further you deviate from your 95% pressure either higher or lower, the worse shape your gunna be in. So, 5 cmH2O on the low end is a non starter for you.
Also, a range of 5 cmH2O is (10 cmH2O max - 5 cmH2O min) is lot of pressure change during the night, and just the dramatic pressure changes alone will tend to wake you up, cause leaks, etc.
So, I'd work your way up from a your minimum of 5 until your min pressure is equal to your 95% pressure. Don't do it in one swoop. 7 is a good place to start, but I think eventually you'll need to go higher to somewhere around 9 or 10. Adjust it to 7-12, get used to it, see how the numbers and graphs change for a week.
Hope this helps.
I found the inverse bell curve graph I was talking about :-)
So, this is an aggregation of data from a roughly one month period in 2009 from my APAP machine at the time.
It graphs out my AHI for each pressure for all that aggregated data, ~30 days worth at every pressure.
You can see an inverse bell curve between 6 cmH2O and 18 cmH2O. You an see my sweet spot at 11 cmH2O.
You may also notice that below 6 cmH2O and above 18 cmH2O the data does not support an inverse bell curve. This is because so little time was spent at these pressures due to me tightening my range once the inverse bell curve became obvious, and also because the machine spent more time at the most appropriate pressures for me. The closer you are to 11 cmH2O on this graph, the more data points are behind it. Basically the smaller datasets on the extremes makes for poor quality data.
So the take away here is the further pressure-wise I was from my sweet spot (higher or lower), the worse my AHI became. This was probably the biggest thing I learned about this whole subject early on.
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