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Machine Chasing Leaks?
#1
I often wonder if I'm experiencing some kind of positive feedback that's causing my pressure to (nearly) max out when there's really nothing going on with my breathing. Here's an example from last night:

   

My AHI for the night was 0.0 and the leak rate was never above the large leak threshold. I was asleep during the entire interval shown. Looking at the high-rate flow data, there's nothing remarkable about my breathing - it looks like normal asleep-on-my-side breathing, other than a couple of very shorts hiccups that look like minor arousals.

What strikes me as interesting is the correlation between the Snore data and the leak data. Is the machine misinterpreting "mask farts" as snores and bumping up pressure, thus causing more leaks and more mask noises?

I see this kind of pattern frequently, and it's not uncommon for me to wake up when the pressure (and the noise) gets near the max. I do see other times where the machine is reacting to snore events and the leak rate is zero - the breathing waveform for those events is markedly different than these.
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#2
It's possible. The leak rate is within tolerance as far as the machine is concerned. The pressure does seem to be following the snore.
Double check for any correlation to flow limitation -- if none, then I think you have a valid hypothesis.

Seems like you have two possible approaches: fix the leaks and/or limit max pressure.
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#3
(02-24-2016, 10:27 AM)justMongo Wrote: It's possible. The leak rate is within tolerance as far as the machine is concerned. The pressure does seem to be following the snore.
Double check for any correlation to flow limitation -- if none, then I think you have a valid hypothesis.

Seems like you have two possible approaches: fix the leaks and/or limit max pressure.

I forgot to mention - the flow limitation graph, which I didn't show, was flat at 0 all through this period.

Unfortunately, I need that high pressure if I get onto my back - sounds like more effort on eliminating leaks is in order.
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#4
Try fitting the mask at pressure.

Alternate solution: You could limit upper pressure if you could make sure you cannot roll on your back.
People have come up with all sorts of ways to keep off their back: wear a backpack; or, sew tennis balls into the back of a tee shirt; or wedge a pillow behind you. (So far, no one has suggested a Claymore mine and a pressure switch! -- small joke, sorry.)
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#5
(02-24-2016, 04:38 PM)justMongo Wrote: (So far, no one has suggested a Claymore mine and a pressure switch! -- small joke, sorry.)

But we knew that Mongo would make that suggestion sooner or later. Big Grin
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#6
(02-24-2016, 03:02 PM)cpdaniel Wrote:
(02-24-2016, 10:27 AM)justMongo Wrote: It's possible. The leak rate is within tolerance as far as the machine is concerned. The pressure does seem to be following the snore.
Double check for any correlation to flow limitation -- if none, then I think you have a valid hypothesis.

Seems like you have two possible approaches: fix the leaks and/or limit max pressure.

I forgot to mention - the flow limitation graph, which I didn't show, was flat at 0 all through this period.

Unfortunately, I need that high pressure if I get onto my back - sounds like more effort on eliminating leaks is in order.

I am going to go out on a limb here and say that, if your machine is truly chasing leaks with pressure, there is something wrong with the machine. It can't be too old. I would take it back to the DME, if that is possible and get it replaced.

Best Regards,

PaytonA
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#7
Well this will teach me (maybe) to go back and check data before I open my mouth. I do not agree that the data displayed indicates a correlation between leaks and pressure increase.

The first part of the graphs looks very much like there is a correlation since the pressure and leak rates seem to be tracking one another. After a while, however, the leak rate drops back a little but the pressure continues to climb.

The pressure starts to drop when the leak rate drops to zero but then later the leak rate goes to about 12 l/min but the pressure continues to decrease all of the time that the leak rate is non-zero. This does not look like any kind of correlation to me.

If one was to ask me what prompted the machine to raise the pressure from the available data, I would have to conclude that it followed the vibratory snore values. Are the vibratory snore values caused by a seal that is vibrating due to leakage? I do not know but I have never had my Simplus give me face farts.

To summarize, there is not a correlation between leaks and pressure increases. It does, however, seem that the A10 Aircurve Vauto seems to respond more aggressively to snore values than the S9 VPAP Auto that I use.

Best Regards,

PaytonA
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#8
(02-25-2016, 03:13 PM)PaytonA Wrote: I am going to go out on a limb here and say that, if your machine is truly chasing leaks with pressure, there is something wrong with the machine. It can't be too old. I would take it back to the DME, if that is possible and get it replaced.

The DME is me. The machine is under warranty, but I really don't think it's behaving incorrectly. I do wonder if it's confusing leaks with snores though.

I don't recall reading anything authoritative on how these machines measure snores, but off hand, it seems like it could be hard to distinguish between a snore and a vibratory leak based on just the flow/pressure data that the machine has available.

I'm going to give some mask liners a try and see what sort of difference that makes.
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#9
I have had face farts with simplus, just lucky I guess. My trick for higher pressure when I used that mask was to get it set and floating just perfect so the gasket part was positioned correctly and then tighten the straps, all 4, by about 1/8" to compress the gasket.

The higher the pressure the tighter the straps, but you still have to get that gasket standing up to get a good seal.
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#10
I see the machine increasing pressure based on snores or whatever is being interpreted as a snore. You would need to very closely examine the flow line to see if there might be some reduction in respiratory volume that is also working to increase pressure. I think the leaks were coincidental and insignificant.

Sleepyhead badly needs an update to fully show the IPAP and EPAP pressures on the Aircurve, and properly interpret pressure settings. For all I know there may even be a bug in the leak reporting. Again, a closeup of the flow line would be more revealing here than the empty events chart.
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