Leak Calculation

General Discussion on any topic relating to CPAP and/or Sleep Apnea.
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LSAT
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Leak Calculation

Post by LSAT » Wed Jan 19, 2022 1:03 pm

I am having a discussion with someone about leaks...Is the exhaust from the mask considered in the leak calculation? If so, how?

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Pugsy
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Re: Leak Calculation

Post by Pugsy » Wed Jan 19, 2022 1:58 pm

Depends....on machine and how it gets reported.
ResMed only reports excess leak...and they do take into account the vent rate before reporting somehow but they never really explain exactly how they do it. I suspect that mask type setting plays a part but probably isn't the only factor.
Vent rate gets subtracted before ResMed machines ever report a leak. How they come up with the "vent rate"...million dollar question.

Respironics report total leak...as do most of the other brands I think. Means vent rate and excess leak are added together.

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palerider
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Re: Leak Calculation

Post by palerider » Wed Jan 19, 2022 2:33 pm

LSAT wrote:
Wed Jan 19, 2022 1:03 pm
I am having a discussion with someone about leaks...Is the exhaust from the mask considered in the leak calculation? If so, how?
Depends on the machine. Respironics, no. others, not sure.

Resmed, yes. I've watched the VPAP Auto's display when first turning the machine on and the displayed leak varies greatly within the first few breaths, until the machine calculates a baseline vent rate and then the 'leak' settles down to 0 as one breathes in and out.

Someone a few years back posted a thing about the math involved, and it was over my head, but one can make some evaluations by watching the rise and fall of the flow rate.

There are some 'sanity checks' in there somewhere, where if you start off with one of the O2 ports open on a mask, it'll show a baseline leak even with the calculation stuff.

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