My Theory based on Respronics Response

[ChipsXJ]

At this point I am not going to sweat the small leaks unless someone tells me where I my theory is weak/wrong. Based on the information below......my machine compensates for the small leaks easily so there is really no therapeutic loss. So I should only be concerned with Large leaks and not the small ones. Do you agree or disagree?


Below is the response I recieved from Respronics when I submitted this question: "I have the Remstar Auto M series with A-Flex. The machine is reporting a leak rate of 43.49 LPM. My mask manufacturer says that vent rate is 37 lpm @ my pressure of 10 cmh2o. so the leak rate is actually 6.49 lpm, correct? Does the machine compensate for this leak keeping my pressure at 10 cmh2o during the leak? So in essence there is no leak or loss of pressure that will affect therapy? What is the max the machine can compensate for before therapy is affected? Thanks "


"fromService <Service@respironics.com>
tochipsxj

dateThu, Mar 12, 2009 at 10:45 AM
subjectreply/ca
mailed-byrespironics.com

hide details 10:45 AM (20 hours ago) Reply


These machines do compensate for leaks up to approximately 60 LPM depending on pressure settings. You are surely within the compensation ranges for that machine.

Regards,

Product Support"

[luke]

Someone videotaped their pressure for a length of time to check what you are asking.
Here's the thread:

viewtopic.php?f=1&t=37842&st=0&sk=t&sd=a



Bill

[roster]

Your leak rate is OK.

I believe Respironics is giving you a number, 60 lpm, for which the machine could compensate at the max machine pressure of 20 cm.

At 10 cm pressure, for instance, I would feel comfortable that the machine could compensate for a leak of 75 to 100 lpm.

Personally, I like to keep mine under 75 cm.

Fortunately, it is always around 40 cm.

[ozij]

I agree.
The major issue with small leaks is whether they, or the machine's adjustment to them disrupt your sleep.
And then, there are masks that mention a +- error rate on the vent measurement as well.
O.

[DreamStalker]

I agree with above comments when using CPAP mode.

In APAP mode however, the auto adjusting pressure sensor is sensitive to small changes in pressure. The higher your leak rate, the more error or loss of sensitivity there will be to the auto adjusting pressure sensor. That I beleive is the reason that my AHI has always gone up the few times I have slept with a FF mask which always had higher leak rates.

[ozij]

In my machine, when I leak in auto mode, the pressure is higher - which makes sense, since it has to supply additional pressure to compensate for that which is lost by leaks.

Your higher AHI with a Full Face Mask, DreamStalker, could be a result of having your mouth open - that raises AHI for most people. Links posted on this thread

The compensation, if not properly calculated may cause confusion in the recommended 90% perssure, since it would be pressure with a compensation for leaks, but why would leaks automatically cause a loss of sensitivity?

O.

[roster]

O and DS,

I don't have much experience with the auto since I use straight CPAP setting. But I do remember when the Hybrid mask was introduced it had a high design vent rate. They soon retooled for a lower vent rate, because the original vent rate was "confusing" autos and causing them to run up the volume.

[SharkBait]

These machines do compensate for leaks up to approximately 60 LPM depending on pressure settings. You are surely within the compensation ranges for that machine.

Regards,

Product Support"

Good info.

I have a F&P FlexiFit HC432 that seems to feel okay and the best I can do is a leak rate of around 10 LPM, but yet it feels to me like there is no leak. The night before last I had a leak rate of around 18 LPM, and my numbers were absolutely horrendous (relatively speaking). AHI of around 20.0!!! And my snoring was off the charts. This wasn't random noise being registered; I woke myself up snoring.

I went back to my Swift LT with taped mouth last night -- Leak rate of around 2 LPM and a 1.5 AHI.

I'm struggling for how the difference can be anything other than my machine not compensating for leak, but the data sample is pretty small so it's hard to reach a conclusion yet. Next time I try that FFM (which I do like), I'll probably go 10-16 APAP and see what goes.

I'm a little concerned about my machine. With the FFM it doesn't feel like it's really blowing and I snore like a dog. I might also try turning off C-Flex...

[The Texan]

Question about reading the LEAK information on Encore Pro. There are 4 sections, Avg max leak, Avg 90% leak, Avg leak and Avg large leak. What does each stand for and what should I be looking for. Mine, with my equipment are, in order, 98.7, 39.0, 33.6, 0. Are these good, bad or what? Maybe once I understand what I'm looking at, then I will understand Respironics response to the OP.

[SharkBait]

Question about reading the LEAK information on Encore Pro. There are 4 sections, Avg max leak, Avg 90% leak, Avg leak and Avg large leak. What does each stand for and what should I be looking for. Mine, with my equipment are, in order, 98.7, 39.0, 33.6, 0. Are these good, bad or what? Maybe once I understand what I'm looking at, then I will understand Respironics response to the OP.

Avg Leak = All of your leaks averaged.

I pay particular attention to Average Leak.

Your mask will have some documentation that will show the vent rate which is "designed link" to flush out CO2. Your actual REAL avg leak is that vent rate (which varies based on your pressure) subtracted from your avg leak rate.

If your pressure is 10, then vent rate looks like around 24 so your actual leak would be 33.6 - 24 or 9.6 LPM.
If your pressure is 12, then vent rate looks like around 29 so your actual leak would be 33.6 - 29 or 4.6 LPM.

[jnk]

. . . why would leaks automatically cause a loss of sensitivity?

O.

I am under the impression that very large leaks can affect my auto's ability to discern what is happening, but I am not sure whether that principle can be extended to other types of leaks. I would assume that intermittent leaks and leaks with constantly changing wide variations might confuse it too, but I don't know. Seems to me that autos get confused often enough without leaks!

"A leak rate of more than 24 L/min (0.4 L/s) affects the accuracy of other measurements . . . The accuracy of apnea and hypopnea logging will be degraded by high mask leak (0.4L/s or more). . . . Problem: Pressure rises inappropriately (in VAuto mode)." Possible Cause: . . . Cushion seated incorrectly causing excessive leak."--ResMed VPAP Auto Clinical Manual (referring, I believe, to rate above intended vent rate).

[DreamStalker]

In my machine, when I leak in auto mode, the pressure is higher - which makes sense, since it has to supply additional pressure to compensate for that which is lost by leaks.

Your higher AHI with a Full Face Mask, DreamStalker, could be a result of having your mouth open - that raises AHI for most people. Links posted on this thread

The compensation, if not properly calculated may cause confusion in the recommended 90% perssure, since it would be pressure with a compensation for leaks, but why would leaks automatically cause a loss of sensitivity?

O.

Higher leaks result in higher "flow" rates. The higher flow rates reduce the sensitivity to changes in flow rates that occur as a result of your breathing.

CPAP mainatians a constant pressure regardless of leak rate (rates below what was quoted by Respironics official).

Because APAP does NOT maintain constant pressure but rather adjusts to higher or lower pressure depending upon air flow, the air flow (ie. leak rate) will affect what pressure the machine uses which in turn may affect the AHI.

[elader]

In my machine, when I leak in auto mode, the pressure is higher - which makes sense, since it has to supply additional pressure to compensate for that which is lost by leaks.

O.

No I don't think so - there is an 'auto' aspect to every cpap machine. Even the basic M series has the ability to hold a 10cM pressure with a non-serious leak. This means that all cpap machines have to be able to increase air delivery to compensate for the leak, the pressure should stay the same.

[luke]

but why would leaks automatically cause a loss of sensitivity?

I think you would have to get into the design of the flow sensor and pressure sensor inside the unit to figure that out.
If I had to guess it would be because the sensor's themselves are most accurate around a nominal pressure or a nominal flow rate
with the sensitivity getting less as you depart from that nominal value. That of course would be known only by Respironics and the
manufacturer of the sensors themselves.
I agree with Elader that even with cpap there's an "auto" aspect to it. Are auto's really doing double-duty then?
Maybe that's why some people here have reported doing better with straight cpap.
The auto's could be easily confused ....I know I am when I'm overworked !

Bill

[SharkBait]

Hey! Let's keep the noise level down in here...