Flow limitation

[DanEm]

I have once more reviewed my data.
Since the pressure I get in the mask is the EPAP, I removed the other from the graph.

I also filtered my data to exclude sleeps with less than 15 minutes' duration.

The following two sets of values come from the csv exported by OSCAR.

1. The EPAP values are those in the column with the heading "95% EPAP".
   
2. The Flow Limitation values are those in the column with the heading "95% Flow Limit.".
   

The EPR values were taken from OSCAR statistics page under "Changes to Device Settings".

The EPR 3 value corresponds to "EPR: Full Time 3 cmH2O"
The EPR 0 value corresponds to "EPR: Ramp Only 3 cmH2O"

I also chose to show EPR = 0 for one exception when I had "EPR: Off" from Aug 31 to Sep 2.

I still see flow limitation going up when pressure goes down except for the rightmost pressure peak where flow limitation goes up and pressure goes up.

Something is not right or I don't understand well enough what is going on.

[Brazen]

@DanEm
I'm super impressed by all these charts!
I think your charts accurately express that your flow limitations are elevated and are not being controlled with your current treatment.
And I think the medical community is in agreement that high flow limitations = poor sleep quality and that Bilevel machine pressure support is often the solution to high flow limitations.
That might be enough data to convince the doctor to write a script for a Bilevel. (depends on the doc)

But are some of the charts trying to make correlations between settings and flow limitations that are really just normal nightly variances or simply presenting the data in other ways? (I admit to being confused about what was being shown in some of those graphs)


I also wonder about the assumption that Flow Limit reported in OSCAR as 0.0-1.0 is equal to percent 0-100.
The article you posted suggested "that only levels of inspiratory flow limitation > 30% be considered in the process of diagnosing obstructive sleep apnea in the absence of an apnea-hypopnea index > 5"
That would be 30%+ of total sleep time.
Is the flow limitation measurement on the ResMed a calculation of the percent of the sleep session you experienced an inspiratory flow limitation or is it a grading on the inspiratory effort of each breath? 

Or am I connecting two separate ideas that you didn't mean to be connected? 


I am in the process of compiling data for a similar discussion with my sleep doctor to try to get a bilevel.  My strategy is simple but I hope still effective.

[DanEm]

Brazen
But are some of the charts trying to make correlations between settings and flow limitations that are really just normal nightly variances or simply presenting the data in other ways? (I admit to being confused about what was being shown in some of those graphs)

Brazen, I am just taking the data and setting up graphs to see if I can get good arguments for a change of machine.

I was told that the only improvement I could get for my sleep was to cut my flow limitation with a BiPAP.
I was told that a 0.1 value or less for FL should be my aim.
So I am looking for arguments to present to my doctor to get a new prescription (my English just got a new word = script :- ).

I admit that the two graphs posted together may be confusing. But I did not modify the data, just the way to present it.

In the last post I did reduce the quantity of information included in the graph and explained what I did.

I also wonder about the assumption that Flow Limit reported in OSCAR as 0.0-1.0 is equal to percent 0-100.

It depends which way ResMed (or OSCAR ?) treats it, more below.

The article you posted suggested "that only levels of inspiratory flow limitation > 30% be considered in the process of diagnosing obstructive sleep apnea in the absence of an apnea-hypopnea index > 5" That would be 30%+ of total sleep time.

The article says:
However, only 5% of asymptomatic individuals will have more than 30% of total sleep time with inspiratory flow limitation. This suggests that only levels of inspiratory flow limitation > 30% be considered in the process of diagnosing obstructive sleep apnea in the absence of an apnea-hypopnea index > 5 and that < 30% of inspiratory flow limitation may be a normal finding in many patients. 

The first part is clear to be a reference to time of sleep.
My interpretation of the second part is that the flow limitation > 30% is the value of the FL ( = 0.3 ), not the time.

In any case, my average FL value when AHI < 5 is 0.42.  A figure of 0.42 is the same as 42% when the maximum value for FL is 1.0 (unless you tell me OSCAR can produce figures greater than 1.0 for FL)
As for the portion of my sleep where I have FL it is much greater than the first reference to 30%. (See the graphic included)

Is the flow limitation measurement on the ResMed a calculation of the percent of the sleep session you experienced an inspiratory flow limitation or is it a grading on the inspiratory effort of each breath? 

I do not know what are the units of the FL figures in OSCAR.  But flow is the volume of fluid (air) that passes in a unit of time. Flow is often measured in units of cubic feet per second (cfs), cubic meters per second (cms), gallons per minute (gpm), or other various units.
OSCAR (or ResMed) must have a reference to express the flow with values from zero to one.  I would guess that when the machine supply the maximum flow is capable, the FL is 0 and if there is no air at all going through, then the FL would be 1 and you would be dead.

I am in the process of compiling data for a similar discussion with my sleep doctor to try to get a bilevel.  My strategy is simple but I hope still effective.

Good luck! 
I will be in that situation in October, I hope.

So I hope I have shed some light....

Frenchy (DanEm)

[Brazen]

Ah. Frenchy! 
I forget that some of my near neighbors speak French first. Yes, script = prescription. 

I think your argument is solid and bi-level is thought to lower flow limits. 
I just don't know that the referenced paper supports the argument because of the unknown calculation within the machine.


Since the flow limit scale is 0-1... yeah, .42 is 42%. But 42% of what?

[Brazen]

For what it's worth...
Both my AHI and flow limits look good (AHI under 2, flow limit under .1) and the thought is that a Bi-level could improve my sleep because of arousal breathing below the threshold of machine flags for CA/H/O/etc.
So, my strategy is marking up my OSCAR screenshots for arousal breathing with flow limits that weren't flagged and the machine didn't work to support.
I'm marking each and calculating an arousal index in hopes that it shows I need the pressure support.

[Gideon]

The 0-1 measure is not a percent figure. It is a value that ResMed calculates based on the shape of the flow rate for the sole purpose of being factored into an algorithm that ResMed uses to increase pressure. It is a reported value and you can often see a definite correlation between pressure increases and higher values of this "index". There is some rough discussion in their patent applications.

[DanEm]

Gideon
The 0-1 measure is not a percent figure. It is a value that ResMed calculates based on the shape of the flow rate for the sole purpose of being factored into an algorithm that ResMed uses to increase pressure

If the value for FL is 0, it should mean there is no flow limitation and air goes in/out freely.

If the value is one (1), does it mean no air is going through?

If not that, then what is the value of one (1) for FL, what does it mean?

And what are all the values in between ( 0.1, 0.2, 0.3 .......), is there a point where one should be concerned?

Here you seem to have a fix on the 0.1 or less for a nice value for FL.
Does the 0.1 come for experience, statistics, ....?

I just read on internet this:
The flow limitation index is calculated by dividing the total number of flow limitation events which occur by the number of hours over which events were recorded.
( https://www.workplacetesting.com/definit...tion-index )

I did not know that flow limitation would be an event that comes on and off?
I don't know if that article is reliable.

Still did not get comments on my last posts with graph!!!!

I do feel like quitting all this, just stop searching, asking questions, keep the machine I have and live with being more tired in the morning than when I went to bed, tired in daytime, going to sleep if I am not active, having concentration problems, etc...

[pholynyk]

The Respironics machines record flow limitations as an on or off flag, so that index could be correct for Respironics machines.

[Brazen]

@DanEm
Do Not Give Up.

I refuse to believe that life just has to be lived feeling exhausted.

Xpap might not be the answer but you really don't know until you have fully optimized and given that treatment a solid try.

Talk to your doc. See what they have to say about your sleep, and your data, and if they have suggestions lean into those. If they don't have suggestions come back here - the experts might have suggestions.

[Jeff8356]

... And what are all the values in between ( 0.1, 0.2, 0.3 .......), is there a point where one should be concerned?

The  Patent application has the following example  for flow limitation (pg 49):

MILD-0.1, MILD_TO_MODERATE-0.5, MODERATE-0.8

Source: https://www.freepatentsonline.com/20110203588.pdf