Mask Leak Rate Experiment

Just as another data point. I have a similar problem with the same CPAP model (Fisher Paykel 244). I am using it with a SWIFT FX mask, not the Quattro.

My leakage rate after a session is always between 50 and 60 liters per minute. The manual for the mask list the flow rate at about 30 liters per minute. I
say "about" because I don't have the mask manual with me.

The display reports my AHI as between 0 and 2, but in my mind, if the leakage is in question, then the AHI numbers might be completely wrong.

The suggestion from the DME was that I might be mouth-breathing and that I should try a chin strap. I am having difficulty to believe that I am, but I suppose that's a possibility. I do have a dry mouth, and did before CPAP as well. No sore throat. I guess I thought for sure that a mouth leak would wake me up, but I guess I could be just leaking around the lips and not actually breathing through my mouth. I'm still skeptical.

I do have a different mask (a non-pillow nose mask) that I took home from my sleep study that I suppose I could try for a night. Then i could see if the leakage rate is any different. But realistically, I am so overwhelmed with other things to do (exhausted and can't concentrate on anything) that I might not get a chance to go find where I put it.

I just sent the data stick in after my 30 day compliance check, so my hope is that some sleep dr. will be looking at it and call me if something is wrong.

So in summary, I'm just letting you know that you're not the only one experiencing this issue.

OK, here's an update. Zeke, unless you have an alter-ego on the apneasupport forum, then there's three of us that have the
same question about the Fisher Paykel Sleepstyle 244 CPAP display of leak rate.

Last night I did try the nose mask (as opposed to nasal pillows) that the sleep center let me take home with me, and slept with it for a night.
Result? 60 L/min.

I think the guy on the other forum using another swift nasal pillow mask, and because I slept a night with a different mask, I'm tend to think that either we are misinterpreting the data, or (much less likely, given FDA validation requirements), that the device simply has a bug in the software.

(As an aside, I found it perplexing that people didn't catch what the poster was saying - they kept questioning him about possible mouth leaks, etc, after he described several times how he progressively sealed off different parts of the system _without_ wearing the mask!)

I did not yet go so far as repeating the same tests as you did, and the person on the other forum did - that is blocking off all the exit routes.
However, we have to consider that we don't know (or does someone?) how the machine determines leak rates. For example, does it simply ignore cases where it senses that it's completely blocked off? If I were designing the software, I would treat a zero flow rate as an exceptional condition and _not_ include it in the stats.

The description of "System Leak" from the operator's manual mentions that a reading below 60 indicates an acceptable amount of leak, for what that's worth.
Also curiously, it says that "... leak is comprised of exhaust flow ... . Exhaust flow is the expected leak at the interface exhalation port ...".
That wording is ambiguous. Is it actually measuring the exhaust port leak, or is it somehow only measuring "delta" flow rate from some steady state point, and assuming that the steady state level is equal to the "expected" exhaust flow leak".

Well again, I'm sure I'm over thinking this thing, but sure does seem odd that there are now three of us who are experiencing the exact same issues with the F/P 244, namely, exhaust rates between 50 and 60 lpm.

So, what do we make of this? I slept with someone twice since I started therapy, and she mentioned that I never snored. The machine never registers more than 2 AHI. I however am just as tired and scattered as before therapy, but that could easily be due to other medical conditions.

Ok, just thought I'ld report back. Of course know I'm in deep sheet because I'm going to be late to work tomorrow due to typing this. Arggg. I need to start leading a normal life again. It's been a constant nightmare.

Larry63,

Thank you for the reply. I have been so busy at work that I have not had the chance to close off all exhaust and see what it reports. I do have the software and the leak rate is pretty consistent. As you have found a third person with the same issue I am starting to believe it could be a bug in the reporting. I think I will run the full closed off exhaust test this weekend and see what happens. I will then see if I can get a response from F&P seeing as my machine is only 3 months old and should still be under warranty.

I will post back later.

Zeke351

Zeke351 wrote:Larry63,

Thank you for the reply. I have been so busy at work that I have not had the chance to close off all exhaust and see what it reports. I do have the software and the leak rate is pretty consistent. As you have found a third person with the same issue I am starting to believe it could be a bug in the reporting. I think I will run the full closed off exhaust test this weekend and see what happens. I will then see if I can get a response from F&P seeing as my machine is only 3 months old and should still be under warranty.

I will post back later.

Zeke351

Well I was able to obtain a data report from the machine.

It does seem that the report matches what the manual says, namely, it says only that anything below 60 LPM is ok. So, the LCD display is not inccorect.
The leak graph even has a horizontal grid line across it at the 60 LPM mark. So I doubt that this is a bug - how about you?

In my case, the leakage does occasionally jump signifanctly to 80 or 100 or so, which I take to be actual leaks.

In my case, I don't think I will try to do those experiments with closing off exhaust points, only because I'm not sure what the software would report
under those extreme cases (e.g. what if has a special case for full unimpeded flow, or full blocked flow).

It

Zeke351 wrote:Bill,

My pressure is set at 10 and I do not use the ramp feature at all. So the leak rate should be around the 36 +/-6 mark. So at the upper end I should be looking at 42 or so NOT 60.

The RT at the DME provider is NO HELP AT ALL! After I explained how thoroughly I tested for leaks she told me to "just ignore it"

When I told her that I was concerned about the AHI and other readings being off if the unit can't figure out the flow rate properly, she basically said I was over thinking it and not to worry. So I asked her how I could trust the data if, like computer programming, if you put crap in you get crap out. She said that because I wasn't using a F&P Mask the unit couldn't adjust for a mask that was from another manufacturer. I then asked her "Isn't a leak rate a leak rate regardless of who makes it and where it leaks?" She got real snippy at that point and said "She was 100% sure that there was nothing wrong with the CPAP machine." This without ever having seen the machine! So I told her, I am 1 month from insurance covering a new mask and I will get a F&P mask at that point and see if there are changes to the leak rate and we will take this up again then. All she could say was that she didn't like F&P's FF masks. I told her that was ok because I love the fit of the Quattro and I could always switch back if I didn't like it.

I think I piss her off because I won't back off just because she thinks she is the expert! Welcome to a thinking CPAP users world!!

Zeke351

Larry,

I still think there is an error in the amount of leakage the machine is reporting. I feel my therapy is going well and do not have a lot of confidence in the number the system is reporting as far as leaks go.

My software readouts do agree with the lcd display which I feel reinforces my point. My leak rate is showing as 62 l/min which would be approximately 37 l/min higher than the leak flow rate of my Quattro mask. Since the software/lcd doesn't adjust for leak flow rate of the mask and just adds up the leak flow rate and actual leakage to get the numbers it uses, I have a difficult time believing my mask is leaking at 37 l/min without me noticing it.

My graph showing my leakage is relatively steady, so while I think the machine is detecting when there is a leak, I do not believe it is reading and computing an accurate number.
This all leads to my greatest area of concern, namely that if the machine is calculating the leak rate incorrectly, can it be computing the AHI and events incorrectly also?
Zeke351

It would be interesting if you could get a loaner of the same model to test it out. I can only tell you that we have two same machines, model M Series. One seems to be calibrated exactly on target so my husband gets the expected leak rate of about 40 lpm at a pressure of 12cms.With the other one his leak rate is about 45 but surprisingly is a quieter machine. Leak line and AHI is good on both. I've asked and have been told this is sometimes a manufacturing glitch and has no impact on therapy, but I would certainly question the leak data on your machines,that seems strange.

I would return machine as defective and if dme can't/won't get a different one, find one that is more concerned with your therapy. She sounds like one I dealt with, but only once. There are a lot of them out there that don't like it when you educate yourself more than them. Most of them only know a product, not therapy issues. I do most of my shopping on-line, and get most of my knowledge from all of you out here. My general Dr. is aware of where I am at and is confident in my therapy. jlk

Contact the manufacturer with your data and mask specs in hand.

Zeke351 wrote:Larry,

I still think there is an error in the amount of leakage the machine is reporting. I feel my therapy is going well and do not have a lot of confidence in the number the system is reporting as far as leaks go.

My software readouts do agree with the lcd display which I feel reinforces my point. My leak rate is showing as 62 l/min which would be approximately 37 l/min higher than the leak flow rate of my Quattro mask. Since the software/lcd doesn't adjust for leak flow rate of the mask and just adds up the leak flow rate and actual leakage to get the numbers it uses, I have a difficult time believing my mask is leaking at 37 l/min without me noticing it.

My graph showing my leakage is relatively steady, so while I think the machine is detecting when there is a leak, I do not believe it is reading and computing an accurate number.
This all leads to my greatest area of concern, namely that if the machine is calculating the leak rate incorrectly, can it be computing the AHI and events incorrectly also?
Zeke351

Zeke, and everyone else - My opinion is the machine is NOT defective. It just somehow reports the leak rates differently. I say this because both in the printed manual and the graph on the reports, it clearly states that leak rates up to 60 lpm are acceptable. Notice that this statement makes no mention of the type of mask, so really think we're fine, and I'm guessing the reporting of events is accurate when the leak rate is below this level. It is too much of a coincidence for three people so far to have the same problem with these machines, and all are reporting leak rates around the 60 lpm level, which is the same level mentioned in the manual.

I don't know how long that this machine has been in the field, but if three of us on the forums are reporting the exact same issue, then it think the most likely scenario is that are CPAPs are working correctly, and this model simply has a different way of reporting leakage. Maybe it works in some different way (not I can imagine how). Of course there could be a design error in this machine, but certainly by now _someone_ somewhere would have noticed it and there would be a recall.

But I agree, it would nice to hear from the manufacturer, if they talk to patients.

What's your opinion, Zeke and everyone else?

Well Larry we will see what F&P have to say. I sent them an e-mail this weekend, but I am not holding out much hope of a response.

My gut is telling me that the unit is functioning fine but it is reporting the leak rate incorrectly. I believe that the calculation is off by approximately 25 l/pm. I am averaging a 62 l/pm leak rate for the last 4 months: Mask Leak Rate of 35 l/pm + 25 l/pm for the inaccuracy would make it 60 l/pm. With me averaging a 62 l/pm leak rate, I can accept that my mask averages a 2 l/pm leak rate from other than the exhaust vents while I sleep. IMHO YMMV

Zeke351

Zeke, be sure the two oxygen ports are properly fitted with the screw in plugs!!!!

ww wrote:Zeke, be sure the two oxygen ports are properly fitted with the screw in plugs!!!!

I am still fairly new to this...what oxygen ports?

I use a fitlife full face thing and it farts and leaks all over the place just no way to stop it I would say its a faulty machine

Zeke351 wrote:

ww wrote:Zeke, be sure the two oxygen ports are properly fitted with the screw in plugs!!!!

I am still fairly new to this...what oxygen ports?

They are the two plastic ports at the bottom level on the front of the plastic mask. There is a soft silicone cover for these two ports, when missing, the mask leakage will increase significantly. You should be able to use a mirror and feel of the leakage from each of the normal vent holes near the top of your nose and then feel at the bottom of the mask near your lower lip as there should be no venting there unless the silicone cover is missing

Thanks ww,

Those are sealed up tight though. Looks like I get to keep looking.

Zeke351