Flow Limitation

I don't understand the concept or phenomenon of 'Flow Limitation'.
This showed up last night:

I think this is the easiest way to explain:
http://img.docstoccdn.com/thumb/orig/39372806.png

Thanks djhall,
I'd appreciate clarification of following graph.
The first obstructive event correlates to a flatenning, while the hypopnea appears so-and-so and the 'unknown' and central events show no obstruction. Is this correct?

There appears to be plenty of 'flatenings'. Anything I can do about it?

You have to zoom in on the flow rate graph and individual breaths to see the flattening and shape of the breaths that might point to flow limitations. You can't see the shapes of the breaths on the FL graph...that's not the flattening that is being talked about.

You have an "unknown" flagged? That normally doesn't happen unless the leak is very large..what do your leaks look like at the time of the unknown?

In the installed ResScan program there is a clinical guide to how to use and that includes a bit more explanation about what you see. You might look at it.
You can find it by clicking on All programs..Find ResScan in the list..click to expand and choose the clinical guide from the choices.

What to do? Normally just a little more pressure prevents or reduces flow limitations. You can't stop them all short of massive pressures though. If that is what you are trying to do.

rebe wrote:I'd appreciate clarification of following graph.
The first obstructive event correlates to a flatenning, while the hypopnea appears so-and-so and the 'unknown' and central events show no obstruction. Is this correct?

Well, first, as Pugsy mentioned, the graph you are looking at isn't the actual waveform of your breathing where you directly see the flattening of individual breaths. That graph you are looking at shows the amount of flattening the software sees in the breathing at that particular point in time. The higher the line on that graph the more flattening the software sees in the waveform.

The OA is a flattening to the point that the breath is completely flattened and you effectively aren't breathing. On the graph you are looking at that results in a temporary spike in the amount of flattening occurring. A Hypopnea is a significant flattening but not a complete blockage, so you would see a smaller spike in that graph, though I don't actually see a blue flag in the events. However, again, that isn't the actual flattening you are seeing but a "trend line" showing periods of more average flattening and periods of less average flattening. CAs (and unknowns) aren't factored in since they aren't caused by airway collapse.

rebe wrote:There appears to be plenty of 'flatenings'. Anything I can do about it?

Not that we would be comfortable recommending from just a 30 minute snippet showing a single OA and some CAs... The bigger picture is more important and we would want to see your total AHI, what events are driving it, what your leaks are like, what your pressure is running, etc. across at least an entire typical night, before making any recommendations. If your first graph is showing what I think it is, namely a full night with one OA, zero H events, and for CAs, and that is a typical night for you, I'd be seriously tempted to tell you not to try fixing something that isn't broken unless you are have some other reason to think your treatment isn't effective. Though I would take a look at leaks if you are seeing unknowns regularly. If the FLs were "growing up" they would start to create H events and then we would want to treat those. If you don't have any H events, you could push the FLs down a little with a 0.5 or 1.0 bump in pressure, but you probably don't need to and you really aren't realistically going to eliminate them entirely.

Thanks Pugsy and djhall,

Pugsy wrote: ... In the installed ResScan program there is a clinical guide to how to use and that includes a bit more explanation about what you see. You might look at it.
You can find it by clicking on All programs..Find ResScan in the list..click to expand and choose the clinical guide from the choices....

I cannot find the 'All programs' or rather don't know where to look for it. Have attempted to zoom after watching the ResMed tutorial.

djhall wrote:...
CAs (and unknowns) aren't factored in since they aren't caused by airway collapse. .. ...

That makes now sense to me.
The night mentioned is not typical.
The first month my AHI was over 5 about half the time (including nights with 13 and 11).
But now it's lower.

rebe wrote:I cannot find the 'All programs' or rather don't know where to look for it. Have attempted to zoom after watching the ResMed tutorial.

All Programs is the option which brings up the full list of programs under the Start button in Windows XP, Vista, and 7. It was replaced in Windows 8 with the Start Screen.