Please - An Explanation Of Flow Limitaions

My original sleep study showed that I had an AHI=60. I have been on CPAP for 6 weeks (7.6 cmH2O), and although my average AHI is now about .2 I still experience fairly severe brain fog at times.

I have been trying a Resmed S9 the last 2 weeks, and I have been observing the data in both Rescan and SLeepyHead. Both programs show a lot of Flow Limitation activity.

So my first question is, What are FL's. In the images below you can see that Rescan displays FL's with 3 waveforms displayed on the Y-axis. SLeepyHead displays FL's with a numerical scale on the Y-axis.

I understand that the perfect Flow Rate graph should be a smooth parabola, and if the flow rate has a flat top, that is an indication of FL's. I imagine the waveforms on the Rescan Y-axis graph reflects the shapes of the flow graph. So my first question is what are the numbers on the Sleepy head graph representing?





In the next image is my personal Flow Graph at a time of high FL's. In my eyes it doesn't look a lot different than some others have posted on this forum. My next question is, could these FL's still be causing my brain fog even though my AHI is vastly improved?. And my final question is, what causes FL's? Are they an indication that the airway is still partially blocked, and that perhaps a little more pressure is still required to open it fully?


Rick

Good questions, Rick.

I look forward to someone who knows answering them, because I'm curious about this as well.

I can't get SleepyHead to show Flow Limitations chart

flyingwithoutwings wrote:I can't get SleepyHead to show Flow Limitations chart

The Flow limitation chart that the OP posted above is from a ResMed S9 machine.
You are using a PR System One machine and it doesn't show Flow limitations in a graph format like the S9 does.
Instead it flags them individually as an event in the top graph on the right...and only in auto adjusting pressure mode.

flyingwithoutwings,

You are using a PR System One machine. The System One's record flow limitation data in a very different way than the Resmed S9's do.

On the PR System Ones, the Flow limitations are only recorded if you are using the machine in Auto mode. If you are using the machine in auto mode, the FL are scored as discrete events as tick marks that appear in the events table and the tick marks are also shown as overlays on the wave flow graph---just like the OAs and the Hs are shown.

On the Resmed S9s, the Flow limitation data is recorded as a continuous function of time. At each sample point during the night, the machine scores how how "happy" it is with the shape of the inspiration part of the wave flow data and this score is then used as the y-coordinate in the flow limitation graph in both Resmed and SleepyHead. But the S9 users don't have any FL "tick marks" in their events table and they do not see a FL index in the summary data in the left sidebar of the daily detailed data in Sleepy Head.

Thanks, I was going crazy looking for that graph and couldn't figure out why I couldn't find it. I do see the Flow Limit on the right.