Acceptable Leak Rate on Resmed ASV machine

[struts]

What is the acceptable leak rate ? I read that it is < 24L/min . Is that correct ?
From my previous experience with trial machine after sleep study, I found that if the leak rate was higher, the AHI was also higher, even the rate <24L/min. 

This also leads to my main quesiton on the proper method of getting a good mask fit.

This was my experience...
I always ran the 'Run Mask Fit' every night to get a good mask fit. 
I always attempted to achieve zero leak. As the 'Run Mask Fit' runs at the max or very high air pressure, 
I ended up always making the mask very tight and very uncomfortable.

[slowriter]

Sometimes you also just have to experiment with different masks.

[staceyburke]

It would be better to use oscar and post the nights sleep. It can be helpful in seeing what type of leak and what that leak causes. We all have leaks and the machine does take care of some of them, it is only important if the leak causes the therapy to suffer. So again, post last nights charts from OSCAR and make sure the leak rate and event and flow and pressure charts are able to be seen. Also the left column - take off the calendar and pie chart so the settings are available.

[Sleeprider]

Struts, all masks have an intentional leak or vent rate that ranges from 24 to 36 L/min depending on design or pressure.  This is to prevent rebreathing of expired air.  Note that leak rate is anywhere from 7 to 7 times the air volume required for respiration, generally 5 to 10 L/min depending on the individual.   In addition, some CPAP machines like Philips report total leaks, while Resmed reports only the excess leak.  So when we talk about an acceptable leak rate, we allow for the designed mask leak and add about 25 L/min for unintentional leak before we reach the large (excessive) leak rate.  That may be as high as 55-60 L/min of total leak depending on variables of mask type and pressure.  What really matters is whether the CPAP can maintain control of the airway at any given leak rate. When we see detected respiratory flow rates drop and a lack of definition in the detection of breathing, that is a good indication that leak is really excessive.  Finally, if leaks are disruptive to sleep they need to be reduced so we can sleep well.

For more details please see the Leak Rate Graph wiki and the Mask Primer

[SarcasticDave94]

I've always used the practice towards using Mask Fit is to get your mask adjustment in the ballpark and you fine tune it while lying down under your therapy pressures. If the mask needs adjusted with extreme headgear tension, it is either the cushion is the wrong size or wrong design for you. If you feel like you need to adjust the mask with a torque wrench, then again something in the mask formula is not correct for you. Change something to get better results. And leaks of ZERO are not required or expected. What is required is the leaks are in a controllable range so the machine can compensate for it and that gives you reasonable comfort.

[struts]

As Resmed only report excess leak rate, I don't need to be concerned with the intentional leak of the mask ,
which in my case, is the FFM, Mirage Quattro. 
When I fit the mask, should I skip the 'Run Mask Fit' and start the normal run to fit the mask based on the reported leak rate ?
The "Run Mask Fit"  always run at the max pressure, I ended up always over tightening the mask. 
What leak rate should I target at while fitting the mask, zero or 12L/min or the large leak rate, 24L/min ?

[mesenteria]

Run the mask fit with the mask adjusted for comfort, not for leakage.  It MUST NOT be overtight! Let the machine determine if there is too much leakage, which it should signify.

Excess leakage should be sufficiently obvious to cause annoyance, or to at least hinder either the onset of sleep or the continuance of sleep.  If the mask fit procedure doesn't render a warning, or an instruction to adjust fit, then you should assume it suffices, and you should assume that it will be that much less prone to leakage at the reduced pressure you have been prescribed.

[struts]

The 'Run Mask Fit' option only show a 'angry' smiley and a 'happy' smiley. What exactly does those smiley indicate ? 'Angry' means > large leak ?, 'Happy' means < large leak or no leak ?
As 'Run Mask Fit' runs at the max air pressure, my experience was that I tended to have to over-tighten the mask to get a 'happy' smiley.
The 'Run Mask Fit' does not show the actual air leak so that I can compromise between the amount of air leak and the comfort.
My original question is about the usefulness of the 'Run Mask Fit', and whether I can just skip it and adjust my mask fitness or tightness based on the previous night sleep data.
or how should I properly use the 'Run Mask Fit'  ?

[SarcasticDave94]

See that red frown up there? Does it cause you nightmares?

Those are the demon twins that will drive you crazy with their arbitrary Red frown or Green grin. Save your sanity by skipping the Mask Fit. What does OSCAR say your leak rate is or how bad or good it was this night or etc.? Mask Fit is not very helpful with no real meaningful info to guide you. I'm serious, just skip the Mask Fit of you'll be fit to be tied.

Learn how to adjust your mask with OSCAR data and how the mask instructions tell you how its done. Whatever it tells you for your mask, do that. All masks will leak a little, otherwise where does the exhaled air go? Obtain a reasonable and controllable leak rate then sleep on it.

[struts]

Dave, 
I agree with you, the angry and happy smiley are just not giving enough granular fit/leak data. 
Most of time, 'Mask Fit' just drove me nut adjusting the tightness. 
I wish the 'Mask Fit' can be more informative and adjustable, e.g. giving me the actual leak at what pressure, and user can set the pressure based on the max pressure from previous night data. 

I also agree with mesenteria to adjust for 'Comfort' not just for 'leakage'. 

I am still waiting for my ASV to be delivered. 
During the time of my trial use of xPAP machine, I thought it was a simple process, and turned out to be a lot complicated than I thought, and I did not get the chance to learn much. 
Now, I try to learn more in order to have a better experience based on my previous beginner's experience.

As the ASV machine starts at the lowest pressure of the setting and only increases the pressure 'on demand', chance is that the max pressure will only happen in the middle of night while I am not awake enough to know what is going on. 
Most likely I can only adjust the mask fit the next night based on the previous night data. 

Not quite interactive and convenient.

I would like to see others' experience of Mask Fit with ASV machine.