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[Treatment] AHI vs Leakage
#1
Sad 
Need help in finding solution to sleeping with my mouth open. Have tried full face and hybrid masks but this gives AHI of 44, and leakage of 97. A more promising approach has been using a nasal mask and tape to keep my mouth shut. (Yes, I have been told that this might be a disaster if I were to throw up in the night, but I am not in the habit of doing this, and until a better solution can be found, I am prepared to accept the risk.) Anyway I have been resetting the display and pressure (9-11) on my Remstar Pro everynight and have succeeded in getting the AHI as low as 11. But, at the same time a mask leakage of 88 was indicated. Another night I obtained an AHI of 13 and leakage of 54. I have been told that reducing the leakage, presumably due to the failure of the mask to be properly fitted, may be the key to reducing the AHI, but from an engineering perspective I find it hard to understand how the machine can determine the difference between a mask leak due to an improper fit, and that which built into the mask itself in order to take care of one's exhale. (The air which escapes from this source is certainly far in excess of anything which I have been able to detect from the mask, or around my mouth.)

Anyway, if anyone out there can make any sense out of this or give me some additional guidance I would certainly apprceiate it. Thank you!
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#2
As I understand it, high leaks produce inaccurate AHI readings. Best to get leaks under control and accurate AHI readings can be taken. Get rid of the tape and get a chin strap.
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#3
With leaks that high, the CPAP machine can't pressurize your airway and it therefore cannot prevent the collapse of your airway. Thus the very purpose of the CPAP therapy is defeated by the leak.

To determine the AHI the machine makes use of a flow meter. When you breathe the reading on the flow rate meter goes up and down. Up when you inhale, down when you exhale. When you stop breathing the flow rate stays steady. When this happens for more than ten seconds the machine scores an apnea. Moreover, the machine sends pressure pulses during an apnea in an attempt to determine if your airway is clear or obstructed. If clear, a CA is scored, if obstructed a OA is scored. I would think that high leak rates would interfere with this type of determination.

The bottom line is this. It doesn't matter what the AHI is when your leak rate is that high because your therapy is compromised by the leak and so is the machine's ability to measure the AHI.

Have you tried a chinstrap? Taping is a foolish and irresponsible practice.
Sleepster
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#4
(08-13-2012, 02:29 PM)glengen Wrote: I find it hard to understand how the machine can determine the difference between a mask leak due to an improper fit, and that which built into the mask itself in order to take care of one's exhale.
Welcome glengen
What machine and mask are you using? Resmed machine in profile
Respironcis and Resmed machines goes about reporting leak in a different way.

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#5
Hi glengen, WELCOME! to the forum.! Have you tried a chinstrap? I would sure TRY LIKE ANYTHING to keep from using tape to keep your mouth closed, I'm sorry you are having so much trouble but hang in there but please, try to get away from using tape.
trish6hundred
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#6
(08-13-2012, 02:29 PM)glengen Wrote: I have been told that reducing the leakage, presumably due to the failure of the mask to be properly fitted, may be the key to reducing the AHI, but from an engineering perspective I find it hard to understand how the machine can determine the difference between a mask leak due to an improper fit, and that which built into the mask itself in order to take care of one's exhale. (The air which escapes from this source is certainly far in excess of anything which I have been able to detect from the mask, or around my mouth.)

Welcome to the group Glengen! Welcome

All masks leak, this is how they flush out carbon dioxide when you exhale. The amount of air that escapes to facilitate this flushing process is a known quantity which increases at a known rate as pressure is increased. This is called intentional leakage. Anything over and above what is used to flush the mask is considered unintentional leakage. Nobody cares about intentional leakage, we want that! It is a good thing as it keep us from suffocating! But at the same time we do want to minimize unintentional leakage in order to allow the pressure to build up in our airway and keep it open to reduce or remove Apneas. I hope that makes sense!
I would tend to agree with the crowd here about chinstrap, not tape! More than just throwing up can cause distress with tape over your mouth. You could have some sort of unforeseen reaction to something and develop serious breathing problems, etc.
As always, YMMV! You do not have to agree or disagree, I am not a professional so my mental meanderings are simply recollections of things from my own life.

PRS1 - Auto - A-Flex x2 - 12.50 - 20 - Humid x2 - Swift FX
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#7
(08-13-2012, 02:51 PM)Sleepster Wrote: With leaks that high, the CPAP machine can't pressurize your airway and it therefore cannot prevent the collapse of your airway. Thus the very purpose of the CPAP therapy is defeated by the leak.

To determine the AHI the machine makes use of a flow meter. When you breathe the reading on the flow rate meter goes up and down. Up when you inhale, down when you exhale. When you stop breathing the flow rate stays steady. When this happens for more than ten seconds the machine scores an apnea. Moreover, the machine sends pressure pulses during an apnea in an attempt to determine if your airway is clear or obstructed. If clear, a CA is scored, if obstructed a OA is scored. I would think that high leak rates would interfere with this type of determination.

The bottom line is this. It doesn't matter what the AHI is when your leak rate is that high because your therapy is compromised by the leak and so is the machine's ability to measure the AHI.

Have you tried a chinstrap? Taping is a foolish and irresponsible practice.

Thank you for your reply. Yes, I have tried the chinstrap. Unfortunately although it will keep my teeth together, it doesn't keep me from opening my lips when I go to sleep. Perhaps there is another way to keep to keep my mouth shut but I havn't figured that out. Upon examining my log for the past week or so there seems to be little, if any, correlaton between the AHI and indicated leakage. The minimum leakage I have obtained is 36 with an AHI of 33. In addition to the results reported in my original post I have obtained an AHI of 14 with leakage of 47. In general my lower values AHI seem to correspond with higher values of leakage, and this presumably makes no sense. This has lead me to wonder if the display is indicating correctly. One further observation: I have set the pressure as high as 11.5, and when I do so I can definitely the pressure trying to push my cheeks out which would seem to indicate that the pressure is present in spite of the indicated leak.

Anyway, thank you again for your initial reply and if you have any additional thoughts, I would certainly appreciate hearing them.
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#8
Glen,

Be careful! Resmed indicates that any leak over 24 l/min (unintentional) can comprimise the ability of the machine to detect apnea events. You may not have low AHI at high leaks, just that the machine looses its ability to detect them efficiently.

As stated, very high leaks may even compromise your therapy, though I have not found a published "number" of what level that is. Be sure to look at your 50% & 95% numbers as well. A single mask slip can make the Max leak very high while you're actually doing okay 95% of the time. The 95% leak rate is what I use for GOOD/BAD looks at my leaks.

Keep posting and let us know how you do.
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#9
(08-13-2012, 03:00 PM)trish6hundred Wrote: Hi glengen, WELCOME! to the forum.! Have you tried a chinstrap? I would sure TRY LIKE ANYTHING to keep from using tape to keep your mouth closed, I'm sorry you are having so much trouble but hang in there but please, try to get away from using tape.

Yes, I have tried the chinstrap keeps the teeth closed, but unfortunately doesn't keep me from opening my lips. I'm beginning to wonder if I can believe what the display is telling me.
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#10
(08-13-2012, 03:59 PM)jdireton Wrote: Glen,

Be careful! Resmed indicates that any leak over 24 l/min (unintentional) can comprimise the ability of the machine to detect apnea events. You may not have low AHI at high leaks, just that the machine looses its ability to detect them efficiently.

As stated, very high leaks may even compromise your therapy, though I have not found a published "number" of what level that is. Be sure to look at your 50% & 95% numbers as well. A single mask slip can make the Max leak very high while you're actually doing okay 95% of the time. The 95% leak rate is what I use for GOOD/BAD looks at my leaks.

Keep posting and let us know how you do.

Many many thanks for your interest and input. But what I fail to understand is that if the leakage is as bad as the machine indicates it would seem that I should be able to recognize it after I have put the mask on. In reality I have been unable to detect any, and it certainly must be much much less than that which has been built into the mask.
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