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[Diagnosis] Low Leak, High UAs, Flow Limit?
#1
Low Leak, High UAs, Flow Limit?
Hi

Trying to understand the results here, and particularly how to use the Flow Limit. graph to understand what is happening.

I have attempted to understand what has been said about Flow Limitation in the various places in this forum (especially in the Wiki such as the RobySue's Beginners Guide and the Data Interpretation links) but still not grasping how to relate the Flow Limit. display to the results I get.

The attached is the first problem I am trying to solve. Admittedly I think I have partly. This machine was mistakenly set in the PAP mode of ASV rather than ASVAuto by the clinicians. In ASV mode the EPAP is fixed and the Pressure Support (PS) can vary between Min PS and Max PS. In ASVAuto the EPAP automatically adjusts between an EPAP Min and EPAP Max depending upon 'inspiratory flow limitation, snore, and obstructive apnoea' (from clinician's guide). So through the night, in ASVAuto the EPAP may decide the Min EPAP isn't doing the trick to stop Apnoea events so it resets its EPAP to a new baseline. The PS is designed to keep the 'respiratory flow even' (though not really sure what this means).

Nonetheless, the attached was using a full face mask, which I gave up using as a consequence of this and previous experiences, but now that I have discovered it will most likely work better if it is in ASVAuto, I am going to trial a full face mask again.

But what I need, as part of that process, is to be able to understand exactly what the attached picture is showing me, especially in relation to how ASVAuto may solve the problem and exactly what the "Flow Limit" graph is telling me. For example, if the machine in ASV mode (as it was in the attached) couldn't adequately address the Apnoeas because it reached its limits (the leak rate was not high), why doesn't the Flow Limit graph show this, or is it? If it is, could someone explain how it is showing that and how that relates to the apnoea events.

PS: The timeframe I am referring to in the attached is between 2215 and 0115.

Thank you kindly
Dream


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#2
RE: Low Leak, High UAs, Flow Limit?
I'll defer to others but will comment that your flow limitation graph looks pretty good; much better than mine when I was using asv. having said that, I don't trust it at all with that machine. something to do with the way asv treats centrals makes accuracy of the fl reporting suspect.
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#3
RE: Low Leak, High UAs, Flow Limit?
Welcome to the forum.


I think you are tucking your chin, and that is causing all the UAs.  No amount of pressure will overcome that.  The typical fix is a soft cervical collar, see the link in my signature.  The collar holds the chin up thus setting the proper cervical alignment.  If you use multiple pillows, use fewer.
Gideon - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter

Download OSCAR
New to Apnea? Helpful tips to ensure success
Soft Cervical Collar
Mask Primer
Dealing with a DME
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#4
RE: Low Leak, High UAs, Flow Limit?
Hi Sheepless,

Your experience of the FL reporting on this machine being suspect certainly helps me feel a bit better about why I couldn't seem to make sense of it. Did you find that there was another parameter that you felt you could rely on in lieu of the flow limitation?

Can I assume that if OSCAR is reporting the FL that ResMed must also be? And if they are, could it mean that ResMed had a certain piece of information they are providing data for that is being displayed in a way that ResMed did not intend?

I have absolutely no clue about these things, so just wondering out loud why ResMed might, or might not do, something with the data they report.

Once again, thanks for reply.
Dream
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#5
RE: Low Leak, High UAs, Flow Limit?
Hi Fred

I will check that out, as it could help, but the issue for me has been using the full face mask. If I use a Nasal Pillow my results are very good normally. The problem is that I don't want to be limited to the nasal pillow, and besides that I am a mouth breather when I sleep, so I have to use a chin strap which is doing my head in.
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#6
RE: Low Leak, High UAs, Flow Limit?
Some aspects on the Flow Limit and the chart: FL on the chart goes between 0 and 1, so if you're seeing activity/events, it's a value represented below 1, as in 0.x, Flow limits are a less restrictive event than a hypopnea which is less than an apnea. Each of the 3 above event types (FL/Hypopnea/Apnea) might cause sleep disruptions in varying degrees per individual sensitivity.
Dave

OSCAR
Standard OSCAR Chart Order
Mask Primer
Dealing With A DME
Soft Cervical Collar Wiki
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEBSITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#7
RE: Low Leak, High UAs, Flow Limit?
Hi SarcasticDave94

Are you saying that the FL is supposed to directly correlate with the OAs, UAs and Hs on the Event Flags graph? So if I see a FL = 1 then I should see a corresponding OA (which it appears may only show in the Event Flags as UAs in any case, or otherwise show in the Flow Rate graph) as ResMed, it seems, may not flag OAs on this machine.

However, I have drilled down into the Flow Rate graph, and have found it difficult to correlate what it is showing and what the FL is showing. which, I am guessing may simply be me not knowing what I am looking at.
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#8
RE: Low Leak, High UAs, Flow Limit?
I'm not certain, but as I see it, the FL chart and the apnea or hypopnea event flags, etc. are probably not directly related within the data seen on OSCAR or other report tools for that matter. I'm not sure how the FL events relate to these others either, other than any of these as an event can cause sleep disruptions.
Dave

OSCAR
Standard OSCAR Chart Order
Mask Primer
Dealing With A DME
Soft Cervical Collar Wiki
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEBSITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#9
RE: Low Leak, High UAs, Flow Limit?
I'm not sure I understand what you're asking in post #4 so try again if I miss.

with apap I had low level flow limitations all night long. someone here calls them 'grassy'. with asv, the low level stuff was obscured by a lot of high 1.0 fl events. these I ignored, assuming they are the result of the machine raising pressure support against central apnea. otoh, although there's probably reason to suspect the fl stats as well, I did take note if I saw an entry in the 95% column. I also felt that I didn't have a significant problem with fl (& mine were worse than what I've seen in your charts so far).

[edit: actually I do have a problem with flow limitations but mostly those following periodic limb movements which asv pressure support cannot overcome, leading to frequent disturbing swings of pressure support. hopefully not something you have to contend with.]
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#10
RE: Low Leak, High UAs, Flow Limit?
I recently went on an ASV machine. I also wear a cervical collar, been wearing one for years, which may help with you constantly maxing out your pressure. When I first started ASV I decided not to wear a collar and my numbers were good but I felt lousy. You need to try one to see if that stops you from maxing out.

The "standard" Resmed ASV protocol is EPAP 5, PS 3-15. That worked pretty good for me, but after a while I went to ASVAuto with a fairly tight range, 5-7, 6-8; 7-9 is where I am right now. Regardless of where you set your EPAP, you need to max out the PS, to see what happens with your pressure. On an ASV the max IPAP is 25, so if your EPAP is 5 your max PS will be 20. On my EPAP 7-9 my PS max is 18.

If you are still pinging at the max of 25, with a soft cervical collar, then hopefully bonjour or other true experts can offer the next steps.

John

Edit Added: One OSCAR graph that is not used much, but I like for ASV, is the Time at Pressure. It gives me a quick snapshot of the pressures where events happen and the pressures where I spend most of the night. Since PS is a wide range, I like to see the majority of the time spent at the lower PS range with little time when the machine is chasing an event.
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