Leaks and OA's?

dsm · Post by **dsm** » Thu Jun 04, 2009 9:50 pm

DoriC wrote:DSM, Wow, and I get upset when hubby's report is showing 18 & 32mins LL these last 2 nights when he's wearing his new mask (same UMFF). I'm starting to wonder if he does better with his old broken in one? I'll be watching that. Do you know why you were having those massive leaks, any changes at that time and how did you correct them? If I'm understanding correctly, the reason your AHIs were so low was that with the LL you weren't getting any real pressure and your machine wasn't recording any of your apneas. Poorly worded but you get the idea. Thanks.

DoriC
At the time, I changed the air hose, checked all over the mask (a comparatively new Quattro F/F masK). I looked at the H/H unit, the join between the H/H & machine.

I ended up tightening the mask and think that ended up fixing it - at the time I just could not figure why the LL was so massive. I took it calmly at first because the machine was saying how great the night looked & to me the data looked much the same as prior nights. By the 3rd night I was getting anxious due to the increasingly poor day times. It is a bit scary as to how quickly therapy can slide downhill.

Point of those charts is how good they looked compared to how I was feeling. I took that experience as an object lesson in how the day times feel rates well above any data these machines feed us.

DSM

dsm · Post by **dsm** » Thu Jun 04, 2009 9:55 pm

-SWS wrote:
dsm wrote:The third chart is the clincher - almost no HI or AI events but massive LL - and by that day I was like
the walking dead.
Well, the machines are very good at scoring apneas. They can't differentiate central from obstructive.

If you're saying that almost no recorded AI events supports any airway collapse theory---let alone as a clincher piece of evidence---then I'll have to politely disagree. If the airway collapses because of a miniscule 50 LPM leak versus a 30 LPM mask-orifice leak, then we have highly improbable airway collapse physics right there. A sudden 20 LPM leak increase causing airway collapse?

How about leaks cause so much awful tactile and auditory sensory input that your sleep was repeatedly disturbed by all the noise and tactile flutter? I can see that, in turn, causing sensory-stimulus/response central apneas---but they would be recorded.

Anyway, the white paper comment made by Berthon-Jones was that obstructive apneas sometimes bring on sudden mask seal breaches because of that little pressure burst in airway fluid dynamics. Also to comment that the CPAP chart by the original poster is not capable of displaying any precursor flow limitations that might have occurred. That's because the machine is being run in CPAP mode instead of APAP mode.

But yes, I do believe that a sudden stepped resistance in airflow ("obstructive apnea") will cause a sufficient instantaneous pressure burst, while using CPAP, that can and does occasionally breach mask seals. I agree with ozij here: the graphic evidence on page one is entirely inconclusive for any kind of firm scientific conclusion. It's apparently plenty of evidence for us message board posters to foster opinions, however.

No, not what I said ? - "If you're saying that almost no recorded AI events supports any airway collapse theory-"
I was supporting Gerald's point that large leaks diminish the therapy. Diminished therapy means reduced airway effectiveness. Reduced airway
effectiveness means not enough airway open or working. The 3rd chart shows me very clearly that LL was reducing my therapy while the machine was saying 'looks great' ???

DSM

dsm · Post by **dsm** » Thu Jun 04, 2009 9:58 pm

-SWS wrote:
<snip>
airway fluid dynamics.
<snip>

SWS
Is this a new science

Any white papers ?

DSM

-SWS · Post by **-SWS** » Thu Jun 04, 2009 10:03 pm

Got it. Large leaks absolutely diminish therapy in a variety of ways. I agree there.

Machines can't cope with them and neither can sleeping humans. But I think small leaks disturb sleeping humans way more than any CPAP machine's ability to compensate. I don't think that's an airway collapse scenario, but it sure is a sleep-disturbing scenario from a sensory input perspective.

You think fluid dynamics don't apply nicely to the human airway? Sleep and respiratory science employ fluid dynamic models all the time on the human airway. You realize science about dynamic gas flow is called "fluid dynamics" right? Air is the fluid gas flowing through the human airway.

dsm · Post by **dsm** » Thu Jun 04, 2009 10:06 pm

-SWS wrote:Got it. Large leaks absolutely diminish therapy in a variety of ways. I agree there.

Machines can't cope with them and neither can sleeping humans. But I think small leaks disturb sleeping humans way more than any CPAP machine's ability to compensate. I don't think that's an airway collapse scenario, but it sure is a sleep-disturbing scenario from a sensory input perspective.

You think fluid dynamics don't apply nicely to the human airway? Sleep and respiratory science employ fluid dynamic models all the time on the human airway. You realize science about dynamic gas flow is called "fluid dynamics" right?

SWS

Air is compressible most fluids aren't - the compressibility alters the behavior of a gas quite distinctly from the behavior of water in the way it flows.

Water as the medium makes for lousy church pipe organs (yeah but thats really about sound not plumbing )

DSM

(really a minor point but applicable).

-SWS · Post by **-SWS** » Thu Jun 04, 2009 10:18 pm

Anyway, the dynamics of air or liquid moving through a vessel have always been modeled using "fluid dynamics". No one ever said "liquid dynamics" as you seem to infer, Doug.

Gas and liquid are both highly fluid. Hence fluid dynamics are routinely employed on both.

-SWS · Post by **-SWS** » Thu Jun 04, 2009 10:24 pm

dsm wrote:
-SWS wrote:
<snip>
airway fluid dynamics.
<snip>
SWS
Is this a new science

Any white papers ?

DSM

Now that you mention it:
http://www.google.com/search?q=%22fluid ... =firefox-a
http://scholar.google.com/scholar?q=%22 ... =en&tab=ws

dsm · Post by **dsm** » Thu Jun 04, 2009 10:25 pm

-SWS wrote:Anyway, the dynamics of air or liquid moving through a vessel have always been modeled using "fluid dynamics". No one ever said "liquid dynamics" as you seem to infer, Doug.

Gas and liquid are both highly fluid. Hence fluid dynamics are routinely employed on both.

Yep thats a very good point

DSM

PS have a good w/e there - we are just about to commence a wet 3 day one here

D

mars · Post by **mars** » Fri Jun 05, 2009 10:29 am

-SWS wrote:

Well, the machines are very good at scoring apneas. They can't differentiate central from obstructive.

I[/quote]

-SWS

Regarding what you say above - my Sandman Auto daily analysis ostensibly gives me an obstructive apnea value, an obstructive hypopnea value, a central apnea value and a central hypopnea value.

Do I now doubt these figures, or were you not including the Sandman Auto in your statement.

cheers

Mars

-SWS · Post by **-SWS** » Fri Jun 05, 2009 10:48 am

Mars wrote:Do I now doubt these figures, or were you not including the Sandman Auto in your statement.

Both of your statements in the above sentence that I have quoted are correct, Mar:

1) I was referring to the APAPs being discussed in this thread until your well-taken Sandman Auto comment appeared (so the original poster's Remstar and Doug's various APAPs),

-and-

2) Detection sensitivity for employing cardiac oscillations to differentiate central apneas is only around 60%---leaving plenty of room for healthy doubt when interpreting your own Sandman Auto charts.

Here's a nice discussion by ozij about that central apnea detection method:
viewtopic.php?f=1&t=36712&p=318714&#p318714
That study's author, Rappoport, is the inventor and patent-holder of the algorithm inside your Sandman Auto, Mar.

remstarcpap · Post by **remstarcpap** » Fri Jun 05, 2009 11:32 am

wow! I go away for a day and there are 39 posts on my topic!

I'm still a little puzzled. Some seem to feel that the small leaks "caused" the OA's. Some seem to feel that perhaps the OA's caused the leaks by making me move around. Others think it's all coincidence, and that the two are not associated at all. Maybe I should try videoing myself sleeping to see what's happening.

Thanks for all the spirited debate (he said feeling more confused than ever), it's what I love about this forum.

-SWS · Post by **-SWS** » Fri Jun 05, 2009 11:45 am

remstarcpap wrote:I'm still a little puzzled. Some seem to feel that the small leaks "caused" the OA's. Some seem to feel that perhaps the OA's caused the leaks by making me move around. Others think it's all coincidence, and that the two are not associated at all.

That Berthon-Jones white paper I had stumbled across but didn't bookmark, expressed that OA's can cause little mask leaks not so much by moving around (yet another likely leak scenario IMO)---but rather because of the ensuing air pressure burst at the onset of an obstructive apnea.

His observation was a matter of lab measurement even more than sound reasoning. That documented scenario does not preclude some of the other possibilities mentioned in this thread IMO.

Your OA-related mask leaks are all of small magnitude and very narrow pulse width, every time OA coincides with little leaks. Those all look like candidate little pressure bursts, each causing brief seal breaches, and those roughly 20 LPM sudden flow increases. I kinda suspect movement-related leaks would manifest with more variability in amplitude and pulse width, than those highly uniform miniature leak spurts that nicely line up with OAs.

robertmarilyn · Post by **robertmarilyn** » Fri Jun 05, 2009 2:52 pm

<snip>
airway fluid dynamics.
<snip>

I would like to nominate that we use the acronym "AFD" for the term "airway fluid dynamics" even though I am not a scientist and even though I probably do not understand the discussion about AFD as well as I should understand it, in order to be allowed to give it an acronym.

mar

DBoone · Post by **DBoone** » Fri Jun 05, 2009 3:06 pm

robertmarilyn wrote:I would like to nominate that we use the acronym "AFD" for the term "airway fluid dynamics" even though I am not a scientist and even though I probably do not understand the discussion about AFD as well as I should understand it, in order to be allowed to give it an acronym.

mar

I agree. After all, how can we have a really intelligent discussion about something without giving it an acronym.

Velbor · Post by **Velbor** » Fri Jun 05, 2009 3:49 pm

remstarcpap wrote:It looks to me like all my OA's are associated with small leaks.

Going back to the start of this thread, before all of the more esoteric musings, there is the chart, and the interpretation.

We humans tend to see patterns, whether or not they exist. Like the "canals" on Mars.

My experience has been that it is VERY difficult to "line up" marks on these charts with any degree of precision. When I check against the timestamp data in the .xml file, "contemporaneous" events often turn out not to be so.

A tick mark represents an event occurring in a 30-second data window. Attempts to "eyeball" correspondences are unreliable. Even attempts to draw vertical lines are unreliable; we are psychologically "programmed" to "tilt" toward finding correspondences.

I count 12 tick marks for OA's. I would count 7 as pretty clearly NOT lining up with the "leak spikes". Five might; or might not. But of course, I have a declared bias NOT to believe what I see, without verification.

Some of the explanations presented for the presumed concurrence might be reasonable, some are stretches, and some are pulling to the point of tearing the fabric. But I question the underlying assumption that there is any correspondence to be explained. Without confirmation from the timestamp data, all of this is tilting at windmills, and sailing on the Martian canals.

Velbor

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