Explanation of Terms

[paulag1955]

I know there is a glossary on this site, but I'm not looking for definitions. I'm looking for definitions of what this chart is really telling me. If my value for Flow Limitations is .43, what is that actually telling me? What's does a high or low value tell me and so on. I'm not a graph person so unfortunately, I need this spelled out for me in words.




I can't be the only one who's struggling with this. Or maybe I can. I don't know. I can't even evaluate my own data at this point.

[Sleeprider]

Paula, flow limitation are partial obstructions of your airway during inspiration that slow the rate of flow as your inhale normally reaches its peak. This results in a flattened, downward-sloping or chair-shaped inspiratory wave form. Let's break this down.

If you can locate a place on your detail chart and zoom in on that time, particularly the Flow Rate, we can show you exactly what it means. To setup your chart, find a time of high flow limitation on the flow limit graph, and click until only 2-minutes of time are showing. Now on your flow rate graph, Right-click on the title in the left margin and select Dotted Lines, and put a check-mark next to Zero. This will give you a line on the zero flow of your flow rate. Everything above the line is inhale, everything below is exhale.

Finally, take a screenshot of the close-up of the flow limited flow rate you are looking at. We can discuss it. The Beginner's Guide to Sleepyhead in my signature also discusses flow limitation http://www.apneaboard.com/wiki/index.php...imitations .

This is the kind of image we are looking for:

[Walla Walla]

I'll try to explain. On your Flow Limitations the min is zero the max is 1.0. So looking at your data your minimum FL was 0 or no limitations of your airway. Your Med. was .02 which means half the time you had .02 of 1 or more limitation and less than .02 the other half. 95% level you 0.18 of 1 limitation which means at or below 95% percent of the time. So far you have very little in the way of limitations to your airway. Finally the maximum limitation for the night was .43 which means your airway closed 43% of the way once. This pretty much shows the ebb and flow of limitations to the airway throughout the night. Now if your airway limitation reaches a certain level for 10 seconds or more it becomes an event. On the ResMed it would be 50% limitation or more for 10 or more seconds.

Hope that helps.

[Sleeprider]

I'll just add, you can look at certain members like HalfAsleep and see what "real" flow limitation looks like with central apnea. The paradox is flow limitation is considered obstructive, but we almost universally see it in CSA patients throughout the night. The flow limitations cause the auto CPAP to increase pressure, which is why we had to fix your maximum pressure to prevent it from rising in the presence of flow limitation.

[paulag1955]

Two minutes.



And an even closer view.

[Sleeprider]

that is pretty much the definition of a 30-40% flow limitation. The chart does not tell us why, but these breaths are clearly not the nice rounded peaks we hope to see. As a bonus, you gave us the RERA which is the partial arousal from this flow limited breathing, and even the recovery breath is flow-limited.

[paulag1955]

So a value of 1 is a total obstruction, but it would be flagged as an event, right?

Does it make any sense that my CA and hypopnea events are going up as my leaks are going down?

[jaswilliams]

When the mask is leaking the machine cannot accurately measure the airflow so it can miss events

[Sleeprider]

So a value of 1 is a total obstruction, but it would be flagged as an event, right?

Does it make any sense that my CA and hypopnea events are going up as my leaks are going down?

A value of 1 may not be an apnea, but is usually a highly distorted respiratory wave form. I think the FL scale is not a direct percentage, but there is no documentation as far as I know. The scale is used by Resmed, generated by the machine and graphed by Sleepyhead.  A 100% flow limit is an apnea, but a FL of 1 may not be.

[paulag1955]

I am pondering this. Thank you, everyone, for your input.