Flow limits & Oscar graph

[raylock1]

       
I guess I don't understand how the Oscar graphs display information.  The attached daily Oscar report graph for flow limits shows a lot of flow limits, some ranging up to the max marking of one.   The  statistics summary shows a max of .63 which appears to be the level of the Max line on the graph.  Many flow limits on the graph appear to be significantly greater than this value.  I  am clearly missing something.  The statistics summary also shows the med (average?) as zero and the 95% level as zero.  I don't understand what the 95% number means.  Many lines on the graph exceed that but yet the summary shows zero.  I clearly need an education in how/what the display and summary show.  

As to the health picture,  since I have been using the AVS, the AHI number is usually zero or a small fraction above that.  I sleep through the night, usually getting eight to nine hours sleep rather than the five or six I was getting before.  I do not have to take afternoon naps but fatigue still continues.  I was told not to worry about the flow limits before, but I assume they are captured for a reason.  I have also attached a copy of a three minute chart with flow limits.  To my untrained eye there is nothing significant.  Any thoughts would be appreciated.

Thanks
Ray

[Gideon]

Check in "Preferences" to see how the "Max" is calculated. 100% 99% 0r 95%

[raylock1]

So does that means that the max is the total aggregate flow limits (total time which they exist) divided by total time being measured?  I guess that would explain why the med and 95% are zero if they are so small in the aggregate as to be rounded to zero.  However, they are not small if looked at over a short duration, say a few minutes.  Do these have any affect on the quality of sleep?

I don't think I am getting it yet.  

Learning mode
Ray

[Sleeprider]

It gets a little more complicated with ASV, but I agree the section you zoomed on has some appreciable flow limitation not reflected in the statistics. While your results are pretty good I think you would benefit from a PS min of 2-3 cm. This will give you enough assist or pressure support to mostly eradicate the inspiration flattening we see.

[GuyScharf]

So does that means that the max is the total aggregate flow limits (total time which they exist) divided by total time being measured?  I guess that would explain why the med and 95% are zero if they are so small in the aggregate as to be rounded to zero.

The ResMed machines report a "flow limitation index" every 2 seconds (I think that's the frequency).  The index is a value between 0 and 1.  I don't think anyone knows how the machine calculates that number, except that 0 is no limitation and 1 is total limitation.  For an 8-hour night, with a report every 2 seconds, that's 14,400 numbers reported.

Now, imagine sorting those numbers from the lowest to the highest value.  Pick the one in the middle of the resulting sorted list.  That's the "median."  Flow limit median is usually 0 as there are a lot more reports with 0 than other numbers.

The 95% and "Max" numbers are percentiles.  So the number under 95% means that 95% of the measurements have a value below that number.  Again, zero is not an uncommon value even with noticeable flow limitations.  (My OSCAR report has been showing 0.11 at the 95 percentile, which I am told is fairly high.)

"Max" is a misnomer and means different things on different machines.  It is also a percentile number and, with ResMed, I think is something like 99% or 99.5%.  So the number you see is the highest value after discarding the top 1% (or 0.5%?) of the values. (With some other machines and preferences settings, "max" actually means "maximum value seen".  But that's not the case with ResMed.)

It is on our work list to try to clarify that "max" label since it isn't really a max value.

[raylock1]

It gets a little more complicated with ASV, but I agree the section you zoomed on has some appreciable flow limitation not reflected in the statistics.  While your results are pretty good I think you would benefit from a PS min of 2-3 cm. This will give you enough assist or pressure support to mostly eradicate the inspiration flattening  we see.

Thank you Sleeprider.  I increased the PS min to 2cm last night and saw some reduction in the flow limitations and inspiration curve flattening.  I will increase the PS min to 3 tonight and post the results tomorrow.  Thanks again for your input
Ray

[raylock1]

Thank you GuyScharf.  It really helps to have some understanding of the information that Oscar uses to create the graph and statistics.  Your feedback is greatly appreciated.