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The Flow Limitation (FL) graphs that we see in ResScan graphs from ResMed's machines has nothing in common with the Flow graph. While the Flow graph is an analogical respiration value of the flow rate over time, the FL is a symbolic bar chart of the levels of the Flatness of the respiration waves. The machine picks waves at random and assign an out of roundness scale of the shape of the top of the wave from a sinusoidal shape. Resmed combines the RERA and the UAR under the Flow Limitation, graph.

The following is a schematic illustration how it's done:

avi123 wrote:The Flow Limitation (FL) graphs that we see in ResScan graphs from ResMed's machines has nothing in common with the Flow graph. While the Flow graph is an analogical respiration value of the flow rate over time, the FL is a symbolic indication bar diagram of the levels of the Flatness of the respiration waves. The machine picks waves at random and assign an out of roundness scale of the top wave shape from a sinusoidal shape. The higher the RERA the UAR and the Flow Limitation, in the upper airway (nose, mouth, throat), the flatter the respiration waves shapes become.

The following is a schematic illustration how it's done:
IMAGE

Just to be whether I'm on the right track: How similar is the partially-obstructed wave to something like asthma or bronchitis?

DD,

Symptoms related to obstructive sleep apnoea are common in subjects with asthma, chronic bronchitis and rhinitis in a general population
L.-G. LARSSON, A. LINDBERG, K.A. FRANKLIN, B. LUNDBÄCK

Received 8 November 2000; accepted 9 February 2001.

Abstract

The purpose of this study was to examine the prevalence of self-reported snoring, apnoeas and daytime sleepiness in relation to chronic bronchitis, recurrent wheeze, physician-diagnosed asthma and rhinitis.

This was a questionnaire study in a representative sample of a general population. The study was a part of the Obstructive Lung Disease in Northern Sweden Studies (OLIN). A total of 5424 subjects aged 20–69 years, born on the 15th day of each month, participated in the study. Eligible answers were obtained from 4648 subjects (85·7%).

Having snoring as a problem was reported by 10·7%. Among subjects with chronic bronchitis it was reported by 25·9%, with recurrent wheeze by 21·3%, with physician-diagnosed asthma by 17·9%, and with rhinitis by 14·7%. Relatives' concerns of witnessed apnoea was reported by 6·8% of all subjects, while among subjects with chronic bronchitis it was reported by 18·1%, with recurrent wheeze by 17·1%, with physician-diagnosed asthma by 14·3%, and with rhinitis by 9·1%. After correction for age, gender and smoking habits, chronic bronchitis, rhinitis, asthma, and current smoking were significantly related, with snoring as a problem and with relatives' concern of witnessed apnoeas. Symptoms of daytime sleepiness were significantly related with concern of witnessed apnoeas, chronic bronchitis, snoring as a problem, recurrent wheeze and age 50–59 years.

In conclusion, respiratory symptoms and conditions affecting mainly the lower respiratory tract, such as chronic bronchitis and asthma, were related with symptoms common in obstructive sleep apnoea.

Keywords: snoring, sleep apnoea, chronic bronchitis, rhinitis, asthma, epidemiology.

No full text is available. To read the body of this article, please view the PDF online.

f1 Correspondence should be addressed to: Lars-Gunnar Larsson, M.D., Department of Medicine, Division of Respiratory Medicine and Allergy, Sunderby Central Hospital of Norrbotten, SE-971 80 Luleå, Sweden. Fax: +46-920 283350; E-mail: lars-gunnar.larsson@nll.se PII: S0954-6111(01)91054-6

doi:10.1053/rmed.2001.1054

© 2001 Harcourt Publishers Ltd. All rights reserved.

« PreviousNext »Respiratory Medicine
Volume 95, Issue 5 , Pages 423-429, May 2001.

This link does not work:

http://www.resmedjournal.com/article/S0 ... 6/abstract

Check also:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3125056/

Also:

Respir Med. 2001 May;95(5):423-9.

Symptoms related to obstructive sleep apnoea are common in subjects with asthma, chronic bronchitis and rhinitis in a general population.

Larsson LG, Lindberg A, Franklin KA, Lundbäck B.

DreamDiver wrote:

JohnBFisher wrote:...

JohnBFisher wrote:I find the Quattro FX mask quite comfortable. I use a mask liner, which helps the seal hold. And when it does not, it tends to not be as loud when it leaks.

I've got a quattro that I've been using the last few nights because my go-to mask seems to be wearing out (large leakage for no visible reason). I have been thinking about trying the Quattro FX. Thanks.

I have a lightly used Quattro FX you can have, DreamDiver, if you can use a size Medium. If so, send me your address. If it doesn't work for you, send it on to Pugsy's box to donate where needed.

StuUnderPressure wrote:

DreamDiver wrote:

Papit wrote: -Nate and DreamDiver, you put me on the right track with your comments and questions. I can now bring up both Flow and Flow Limitation in the Detailed Graphs.

Me smacking my forehead. "!" I should have remembered the first thing to check is whether or not some graphs are simply omitted from the graphs section. Simple solution.

I can also see both the Flow & Flow Limitation in the Detailed Graphs in my plain vanilla S9 AutoSet.
As some have already said, all you have to do is choose to include them.
So, if you are not now seeing some graphs you hear others refer to, you may have to simply go in & "choose" to see those graphs.

Exactly, but it sure was easier said than done. It took multiple attempts and finally worked for me only by going through the Reports path. Also, as Nate pointed out, each user must make sure he has selected his machine type (cpap, apap, bipap, or asv) in the right place in his Profile.

Any other ASV users seeing very high Flow Limitation spikes once pulling up that graph? If so, while I'll run it by my doc, I do believe that John has it right that they are merely an artifact of the ASV algorithm. If that's so, they should note in parenthesis "(not for ASV)". You'll notice that they inserted parenthetical notes next to several other graph selections in the list of available graphs.

Thanks Dori, Randy, SirNoddinOff. This clearly is outstanding technology. Fortunately I have good insurance to cover most of it. But for anyone who doesn't, and what I was going to do if there was an insurance problem, they can consider used and open-box unused machines at lower prices at SecondWindCPAP.com and there are other similar websites. SecondWindCPAP advertises that they clean used equipment, check machine calibration and apply your Rx pressure settings before shipping. And of course there is Craigs List and others, but you need to be able to do your own settings, etc. however the prices are often quite reasonable.

Anyone who has used secondwind want to tell us what their experience has been?

DoriC wrote:

Randyp1234 wrote:Whoo Hooo!!! Good feeling isn't it? I had a couple 0.0.nights recently also. . . . Randy

Congrats!! So the worst that can happen is that the machine "malfunctioned" and you really had an AHI=0.1!

Sir NoddinOff wrote:The results you are getting with your machine are often the results one sees with modern ASV technology. . . . However, for me, the real miracle is how anyone can afford an ASV machine. Example https://www.cpap.com/productpage/pr-60- ... anced.html
And that's without a hose, humidifier or mask PS... there was one being sold in the SF Bay area recently for $500. Wonder what happened to it?

Papit, can you please show up- todate graphs of your treatment in ResScan Report?
Similar to the following but add the Leak and Snore graphs and cover the whole night.
Can you omit the Flow graph but still show the Flow Limitation?
Please indicate at what mode the machine was set.

avi123 wrote:Papit, can you please show up- todate graphs of your treatment in ResScan Report?
Similar to the following but add the Leak and Snore graphs and cover the whole night.
Can you omit the Flow graph but still show the Flow Limitation?
Please indicate at what mode the machine was set. . . . (earlier image)

The mode my machine is set for is "ASV" (vs. "ASV Auto" which is another available mode selection). Here are the graphs for (7/1/13) yesterday. I'll show SH's first because they cover the 6-hour sleep clearer than ResScan. ResScan's graphs follow SH's. But notice that ResScan graphs include the portion of the previous (6/30/2013) day's sleep up until the 12:00noon cutoff. So the stats are slightly different and the latter graphs a little bit confusing. My treatment for these first 3 weeks on the ASV are shown at bottom in the Report's Summary graphs.

SleepyHead


ResScan Report graphs



First 3 weeks treatment on ASV 6/10 - 7/1/13 (Topmost graph is Tidal Volume)

Papit, are you actually not sleeping during the night?

JohnBFisher wrote: I think the "flow limitation" is an artifact of the algorithm used to identify possible limitation of flow and a precursor to snoring.

John's guess might be spot on. Papit, that hypothesis is fairly easy to test. In Resscan's top window panes set up the FL and detailed flow graphs at 8 hours resolution, one graph on top of each other. Use the mouse to drag the individual graphs either higher or lower. Then, in the bottom window panes, set up the FL and detailed flow graphs in 1 minute resolution---also one graph on top of the other. Now click the top graphs right where severe FL is scored. Then use the left and right arrows at the bottom of the 1-minute graphs to scroll back and forth for detailed viewing.

Are the 1-minute flow curves rounded at the tops, or severely distorted? If the 1-minute flow graphs are nice and rounded, then you are probably looking at reporting or interpretation artifact in the algorithm as John suspects. If, on the other hand, the 1-minute flow graphs are moderately or severely distorted at the tops, then you are probably looking at obstructive flow limitation. Generally, central phenomena will have rounded flow tops while obstructive phenomena will have distorted wave tops (deviating from sinusoid). Mixed phenomena can have both over the course of several breaths. Additionally, mixed and central phenomena will often present with flow-amplitude waxing and waning known as periodic breathing. Cheyne-Stokes is one of many possible periodic breathing types. I also think your periodic breathing does not fit the classic Cheyne-Stokes pattern.

Back to FL analysis. If you observe FL by examining wave tops at 1-minute resolution, AND you now see more severe residual FL than you have on past xPAP treatment platforms, then your residual FL might be iatrogenic vocal cord closures thanks to much larger PS values on ASV. Even "normal" test subjects tend to present vocal cord closures/adduction in response to high PS values:

V F Parreira, et al wrote: Increases in inspiratory pressure did not always lead to increases in effective ventilation reaching the lungs. This was due to a significant narrowing of the glottis by adduction of the vocal cords in all subjects.

http://www.atsjournals.org/doi/abs/10.1 ... .5.8630611

I wouldn't worry about that phenomenon if you are sleeping better and feeling better by day. And if you are experiencing iatrogenic vocal cord adduction in response to high PS values, you may very well see those go away with time and physiologic adaptation. Alternately, you might want to eventually experiment by limiting PS max.

-SWS, how can I tell if the following out of roundness of my respiration wave shapes were true or artifacts? Notice that the Flow Limitation graph did respond by rising:

(Use un zoomed Window to see the following graphs)



At other times the wave shapes are rounder:



But, there were occasions when my wave shapes were really flat although the FL graph (above it) has not shown it to be so:

Hi Avi. This is an exercise in applying heuristic judgment to validate/invalidate Rescan's FL scoring. The algorithmic artifact (or interpretive scoring error) that John spoke of stands to show up in the FL graph---not the raw flow graph. Why? The "flow limitation" graph reflects Rescan's algorithmic scoring or interpretation. By contrast the raw "flow" graph reflects unscored measurement. So the idea here is for Papit to examine his unscored flow graph at 1-minute resolution, in an attempt to validate or invalidate Rescan's FL scoring.

When we see significant flattening, one or more shoulders, or other distinct deviation from rounded sinusoid on the flow measurement graph, then we're looking at some kind of obstructive narrowing rather than central phenomena. Residual or even iatrogenic breathing phenomena are not always worrisome. Recall that periodic breathing, central apneas, obstructive apneas, flow limitations, hypopneas, etc. all occur with subclinical frequency/severity in the "normal" non-SDB population.

So if Papit's sleep and daytime symptoms are much improved, then a little residual or even iatrogenic FL here and there might be nothing more than benign.

-SWS, do you mean Vocal cord dysfunction (VCD)?

http://emedicine.medscape.com/article/137782-overview



See also:

viewtopic/t16612/Vocal-Cord-Dysfunction ... -Cpap.html

No, Avi. Those "normal" subjects in the study I linked don't have VCD. And Papit probably doesn't have VCD either.

Rather my comment to Papit was that *if* he notices more FL using ASV than previous xPAP platforms, then perhaps ASV's higher PS values are inducing vocal cord adduction. More importantly, the scored FL might be perfectly benign given improved sleep and daytime symptoms.

-SWS wrote:

JohnBFisher wrote: I think the "flow limitation" is an artifact of the algorithm used to identify possible limitation of flow and a precursor to snoring.

John's guess might be spot on. Papit, that hypothesis is fairly easy to test. In Resscan's top window panes set up the FL and detailed flow graphs at 8 hours resolution, one graph on top of each other. Use the mouse to drag the individual graphs either higher or lower. Then, in the bottom window panes, set up the FL and detailed flow graphs in 1 minute resolution---also one graph on top of the other. Now click the top graphs right where severe FL is scored. Then use the left and right arrows at the bottom of the 1-minute graphs to scroll back and forth for detailed viewing.

Are the 1-minute flow curves rounded at the tops, or severely distorted? If the 1-minute flow graphs are nice and rounded, then you are probably looking at reporting or interpretation artifact in the algorithm as John suspects. If, on the other hand, the 1-minute flow graphs are moderately or severely distorted at the tops, then you are probably looking at obstructive flow limitation. Generally, central phenomena will have rounded flow tops while obstructive phenomena will have distorted wave tops (deviating from sinusoid). Mixed phenomena can have both over the course of several breaths. Additionally, mixed and central phenomena will often present with flow-amplitude waxing and waning known as periodic breathing. Cheyne-Stokes is one of many possible periodic breathing types. I also think your periodic breathing does not fit the classic Cheyne-Stokes pattern.

Back to FL analysis. If you observe FL by examining wave tops at 1-minute resolution, AND you now see more severe residual FL than you have on past xPAP treatment platforms, then your residual FL might be iatrogenic vocal cord closures thanks to much larger PS values on ASV. Even "normal" test subjects tend to present vocal cord closures/adduction in response to high PS values . . .

I wouldn't worry about that phenomenon if you are sleeping better and feeling better by day. And if you are experiencing iatrogenic vocal cord adduction in response to high PS values, you may very well see those go away with time and physiologic adaptation. Alternately, you might want to eventually experiment by limiting PS max.

Thank you for the guidance, -SWS. I chose to examine two very elevated graphed 'flow limitations' that occurred at 8:39:25am and 8:40:00am in yesterday's (7/3/13) sleep. As you can see below, as usual, lots of FL spikes were graphed during the sleep. Also pictured are a series of 1-minute duration detailed views of the 1-minute resolution Flow and FL graphs that I scrolled through to examine my breathing flow wave tops before the two strong FLs' occurred, during the FL's, and after the FL's. Please check me on this. (1) It appears that my Flow wave is fairly sinusoidal in shape with relatively minimal distortion at the tops in the absence of FL's. (2) Also, the two FL's examined (typical, after looking at many others during this sleep) had minor/no significant affect in causing distortion to the Flow waves when they occurred. Again, thanks for the clear explanation and the time you took on this.