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Mask Fit and Leakage
I just find it odd...that I have a respironics machine...have an unintentional leak rate over 24lpm...and am being told by a respironics software program that my mask fit is 100% which means my leak rate is WELL below what would be considered a high and unacceptable leak.

no where ...(for my phillip respironics autosv advanced machine)...is there any mention or information about a particular leak rate number making the machine statistics unreliable .

Odd that there would be such a huge discrepancy about leak rates by two relatively new advanced machines
I don't believe anything I hear and only half of what I see
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According to the American Academy of Sleep Medicine, a clinician should use their judgment based on the published intentional leak vs. pressure information published by the mask manufacturer as to whether or not the unintentional leak is acceptable.

That seems to go against ResMed's recommendation of 24L/min. Is it possible that this recommendation is specific to ResMed brand masks?


Quote: There is insufficient evidence for what constitutes a
clinically significant leak given mask fit and other factors;
however, in general, an unacceptable leak for PAP is one that is
substantially higher than the leak recorded at a given pressure
from a well-fitted, applied, and secured interface. The acceptable
leak will always exceed the intentional leak, which depends on
the applied pressure and interface type. The intentional leak vs.
pressure relationship is usually supplied by the manufacturer of
each interface (Consensus).

This recommendation is based on consensus agreement by
the PAP Titration Task Force. The intentional leak of all interfaces increases as pressure increases. The exact amount of leak
also varies with the type of interface. This makes identification
of what constitutes an unacceptable leak value very difficult.
Clinical judgment based on laboratory-specific criteria or the
leak vs. pressure relationship supplied by the manufacturer for
a given interface is recommended. A sudden increase in leak
without a pressure change should alert the technologist to a possible increase in mask/mouth leak.

source: http://www.aasmnet.org/Resources/Clinica...040210.pdf
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I think it is important to keep in mind that there is a difference between identifying the leak level that compromises therapy and the leak level that compromises the proper functioning of the machine and all of its features. 24Lm is the maximum leak level above which ResMed warns the function of the MACHINE may be compromised (i.e. may not differentiate OAs from CAs properly, data may be skewed, may raise or lower pressure improperly, may not be able to raise pressure enough to counter the leak). No Auto machine can overcome large leaks at a certain point - at some point the leaks will prohibit the proper sending and sensing of pulses. PR Auto machines have some threshold of leaks they can't operate efficiently/properly above - PR just doesn't tell us what that is as far as I can tell.

Straight PAP would be completely different - a whole other story.
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Thanks to all that have commented over the last week. I've tried several suggestions and have varying degrees of success at reducing the leaks I am experiencing.

In the last few days, I have managed to keep my leaks at a point where I am mostly waking up with a Smile and an AHI of 0.3 to 0.5 (down from 161 at my sleep study).

As with my original post, I still feel great when I wake up, even without achieving my morning smiley face.

I am wondering about the line of thought that has been mentioned in the last few replies about the 24L/min leak rate being the standard of deciding what is a reasonable leak and an unreasonable one. Specifically, if the pressure is set in the higher ranges (like my 19 cmH2O), doesn't that mean that more air volume per minute is flowing to the mask to maintain that pressure? If so, wouldn't it make sense that even a very brief leak could result in a spike over 24L/min? In other words, if several liters escape in a short amount of time, say 10 seconds, that could push the leak rate for that minute much higher than the remaining 50 seconds of that minute would otherwise register. If 5/6 of the minute has little or no leak, that doesn't seem so bad, but it would still record a spike above an acceptable level of leak for the entire minute.

If this is true, someone with a lower pressure might need to leak for a good portion of a minute to lose 24 L of air, whereas I might lose that in only a few seconds as the pressurized air escapes from the mask into the lower pressure of the room air.

If this logic is accurate, I'm not sure if it makes sense to consider a leak over 24L/min as being that bad. Leaks are bad in general, but it seems like the leak rate target should slide based on pressure settings.

I never was that good at chemistry, so if my thoughts on the relation between pressure and volume are confused, then my whole theory could be nonsense. My recollection is that, all other things being equal-the temperature and composition of the air, then the relationship between pressure and volume is directly proportional (P1V1=P2V2 sort of thing). If anyone would like to correct me, please do so.

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ResMed S9 does own leak calculation ... subtract vents leak rate (intentional leak) at set pressure from total leak and report 95% unintentional leak on the LCD. You only need to select mask type

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