Flow Limitation?

penuel wrote:After I raised the min and max pressures on my S9 APAP by 1 cm each, there is some improvement in the FL, but not enough (EPR = 3)

I have been monitoring my FL's as well and found it difficult to see the effect of pressure changes on the FL graph. Personally I find that the graph looks almost the same from one day to another but the SleepyHead summary data does indeed show differences. I am plotting the median and 95% FL's on an Excel graph to better visualize the effect of pressure changes.

The surprising thing is that the median value is often close to zero which is something you wouldn't expect by looking at the graphs (mine look very much like yours). In fact the maximum value on the table is often exceeded several times on the graph. Perhaps this is a SleepyHead bug.

My understanding of ResMed's point of view historically on FLs in the context of home treatment machines is that an FL is considered a possible precursor to upcoming snoring or OSA-related events, but an FL is not so much considered an event in and of itself. ResMed uses FLs as indicators of the need to increase pressure in an APAP in order to prevent actual events and snoring from happening.

http://www.ncbi.nlm.nih.gov/pubmed/9743 ... t=Abstract
http://www.ncbi.nlm.nih.gov/pubmed/1798 ... t=Abstract

If ResMed were to start considering machine-flagged FLs (which they historicallly have defined as broadly as "a physiological change in the status of the upper airway") to be events in and of themselves, they would then have to find something to consider precursors to FLs to begin responding to whatever those would be named. An FL to ResMed is an instance where the flow curve seems to have a significant change that allows them an indication of the need to preempt the possible upcoming event.

It is useful for ResMed to mark them and report them. Our job as patients, though, in my opinion, is to find the pressure that (1) prevents actual events and that (2) makes us feel most rested and alert the next day--without worrying too much about the machine's reporting of pre-events that it chose to react to.

In my opinion.

But hey, that's just me.

About JNK post, imo, a lot of water came down to Jordan river since Jeff's reference to 1981 report.

What Resmed has in mind about measuring Flow Limitation (FL) has nothing to do with the more recent findings of the medical nature of FL.

In the meantime, the sleep Doc Barry Krakow (Kraiko) posted the following about FL and the Stanford sleep group added lots of new important data on UARs which is included in FL as it is presented in ResScan graph.


IMO, The elevated Flow Limitation that I see in my ResScan graph from my S9 APAP indicate to me that presently I probably have some kind(s) of Medical Condition(s) or mental anguish (see above from Dr Steve Park). This indication is not different than checking my current fever with a thermometer.

See my subsequent posts about Dr Krakow's and the Stanford Sleep group on UARs (included in CPAP's data of FL)

Dr. K's statements about FL/RERA/UARS are, notably, made in the context of NPSG--a test that documents arousals.

My statements, on the other hand, were, as I made clear, made in the context of home-machine-reported airway states that are considered by manufacturers to be precursors to events, not events in and of themselves; home-treatment machines cannot document arousal.

I am fully aware, though, that Dr. K, by his own admission, is not known for taking the mainstream approach to use of PAP machines to treat. He prefers riding the cutting edge of customized approaches for helping people who have not been helped by the mainstream approach. He at times chooses to use machines in ways that differ from what manufacturers intend. I respect him for that.

But that does not change the reasons ResMed chooses to report what they call FLs. They are very proud of how they use FL, since their flagging flow shape is proprietary, not medical-standard. They enjoy rubbing their patents in everybody's face as often as possible.

Anyway, none of that changes the fact that for many people, there is no pressure that will consistently prevent what home machines report as FL. Our choice is simple in treatment--either more pressure or less. When we know that, flagged precursors become less the point than our choosing the best pressure possible for preventing apnea and hypopnea and for improving how we feel the next morning and over time. Anything more than that requires pros using PSG, in my opinion, and no amount of fretting over home-treatment-machine-reported precursors will change that fact.

Then again, I may just be more opinionated than Dr. K, all things considered.

+1 Jeff! I like your advice to KISS! Makes sense to me! Happy Healthy New Year.

DoriC wrote:+1 Jeff! I like your advice to KISS! Makes sense to me! Happy Healthy New Year.

Thanks, Dori.

Today is the day every year when Bono's words echo through my head all day long. I wonder if he was singing about forums?

Yeah...

All is quiet on New Year's Day
A world in white gets underway
I want to be with you
Be with you night and day
Nothing changes on New Year's Day
On New Year's Day

I will be with you again
I will be with you again

Under a blood red sky
A crowd has gathered in black and white
Arms entwined, the chosen few
The newspapers says, says
Say it's true it's true...
And we can break through
Though torn in two
We can be one

I...I will begin again
I...I will begin again

I will be with you again
I will be with you again

https://www.youtube.com/watch?v=ZqeRwGnnVBo

jnk wrote:My understanding of ResMed's point of view historically on FLs in the context of home treatment machines is that an FL is considered a possible precursor to upcoming snoring or OSA-related events, but an FL is not so much considered an event in and of itself. ResMed uses FLs as indicators of the need to increase pressure in an APAP in order to prevent actual events and snoring from happening.

I just want to point out that PR's System One machines record and respond to flow limitations by increasing the pressure when they are run in Auto mode. PR's Auto algorithm responds to FL for the same reason that ResMed's machine's do: PR regards FL as a possible precursor to obstructive events.

It is a shame, however, that PR does not tell us what has to be going on for a FL to be scored as a tick mark. It is also a shame that PR's System One machines do NOT record FL when they are used in fixed pressure mode.

Fascinating - thanks for all the info! So you'd say things look good if the standard AHI is below 5 and the RERA+FL index is also below 5?

robysue wrote: I just want to point out that PR's System One machines record and respond to flow limitations by increasing the pressure when they are run in Auto mode. PR's Auto algorithm responds to FL for the same reason that ResMed's machine's do: PR regards FL as a possible precursor to obstructive events.

Thanks, Robysue. I only highlighted ResMed because of what they've said on the matter. I think Respironics used to stress snores more than flow shape in the past for patent reasons or something. But for all I know, PR machines do a better job than ResMed machines with reacting to precursors these days.

robysue wrote:It is a shame, however, that PR does not tell us what has to be going on for a FL to be scored as a tick mark. It is also a shame that PR's System One machines do NOT record FL when they are used in fixed pressure mode.

I admit that my thinking can be nonstandard, but to my way of thinking it would be silly to report a precursor in a non-auto mode, since the whole point of a treatment machine's keeping track of precursors is to use them to decide whether to raise pressure.

I agree 100% that it is high time the big manufacturers came clean with what is going on in their APAPs. I think some docs don't prescribe them, and discourage their use, just out of spite for how secretive the manufacturers have been on the details of their algorithms. The manufacturers seem to print more disinformation than actual information on these important life-and-death matters.

Good to hear from you, Roster. The real you. Not all the other yous.

Here's a good description on flow limitation .https://www.youtube.com/watch?v=3Ehb7U78P5w

robysue wrote:

jnk wrote:My understanding of ResMed's point of view historically on FLs in the context of home treatment machines is that an FL is considered a possible precursor to upcoming snoring or OSA-related events, but an FL is not so much considered an event in and of itself. ResMed uses FLs as indicators of the need to increase pressure in an APAP in order to prevent actual events and snoring from happening.

I just want to point out that PR's System One machines record and respond to flow limitations by increasing the pressure when they are run in Auto mode. PR's Auto algorithm responds to FL for the same reason that ResMed's machine's do: PR regards FL as a possible precursor to obstructive events.

It is a shame, however, that PR does not tell us what has to be going on for a FL to be scored as a tick mark. It is also a shame that PR's System One machines do NOT record FL when they are used in fixed pressure mode.

If you set min/max to same pressure won't it give you FL? I seem to remember doing that on my Autoset.

penuel wrote:About JNK post, imo, a lot of water came down to Jordan river since Jeff's reference to 1981 report...

Avi, your presentation of flow limitations is interesting. Thank you.

Let me ask you this, can you cite anyone on this forum who had successfully adapted to xpap, i.e., used it through the night with minimal leaks, and obtained a long term AHI less than 5, but still suffered from excessive daytime sleepiness (EDS), who then switched to a bilevel, or equivalent, as suggested by your references and overcame their EDS?

I see people switching to bilevel as a means to tolerate PAP, but I don't recall seeing any who switched after mastering PAP solely to overcome EDS who were successful. Have you?

Jay, you didn't actually read the whold dissertation, did you? Happy New Year!

DoriC wrote:Jay, you didn't actually read the whold dissertation, did you? Happy New Year!

I did, even the part that repeats. But the question was serious and I really would like to hear an answer, either from Avi or a bilevel user.

Happy New Year to you, too.
Jay