Pesky Thoughts on Leak Rates

[Kiralynx]

OK, so, we all know that keeping our leak rates within our mask's parameters is the only way to get reliable data and therapy.

We also know that on straight CPAP, you find the leak chart for your machine, find your pressure, and run up the line to the leak line, and that will tell you what an acceptable leak rate is for that mask.

As, for instance, here is the chart for the Aeiomed Headrest which has become my "summer" mask, since it is so light and cool.



Mrmph. This looks as if the picture will over-run the screen, so I'll just post the URL:

http://www.tnlc.com/Lara/laura/osa/Mask ... illows.jpg

Now, if I consider my leak rate to be determined by my EPAP (6), then my leak rate should be around 18 by the chart. But if my leak rate is determined by my IPAP, then I would have a range from around 24-26 (Ipap = 10-14).

In actual fact, I usually run around 20-21, with the occasional "bad night" of 24-26.

So just how DOES one determine the appropriate leak rate for a Bipap, an Auto, or one of the fancy machines, like my Bipap Auto SV?

[spacetoast]

How is the leak reported to you on the bipap machine? As an average? If so, I would say average the high and low numbers off of the chart to get an idea. The average of 24 and 26 is 25. From my interpretation of the chart, I would say a pressure of 10 corresponds to 23 and 14 corresponds to closer 28 for an average of 25.5

In my ResMed Manual (for my mask), it mentioned that the venting holes are subject to manufacturing tolerances and therefor the leak rate could vary from mask to mask.

If your leak rate is significantly higher or lower, you might want to check your mask. If it is quite a bit lower, you might want to see if your vent holes are plugged, or if you somehow close them off while sleeping.

If I understand your post correctly, you are getting a leak rate of around 20-21 normally? And bad nights are 24-26? If all is well with your mask (you have a good seal), it could be that the 20-21 number is what your mask is really venting at. 20.5 is within 20% of 25.5

[Pugsy]

So just how DOES one determine the appropriate leak rate for a Bipap, an Auto, or one of the fancy machines, like my Bipap Auto SV?

I have an APAP set 10 cm minimum and wide open to 20 cm maximum. Last night I saw 18 cm briefly.

Unless I am seeing large and lengthy leaks, I just "wing" it. I know what my 10 cm pressure vent rate is and I just look to see where I seemed to spend the majority of the time and allow for just a little more. Most of time time my overall average is right close to the normal vent rate for the 10 cm pressure. I figure it is just an average and unless I had a perfectly flat leak line I couldn't expect to come up with a figure unless I wanted to do a whole lot more math than I am inclined to do. I tend to look at the leak rate graph itself and it usually tells me a pretty good story. Obviously I don't have any experience with the fancier machines but this is how I look at my leak rate. It gets mostly a glance now.

[Kiralynx]

viewtopic/t40856/viewtopic.php?p=357821#p357821

Shows some charts from my machine. Leak is presented as an average.

Seems like it might make sense to average EPAP and MaxIpap, thus 18+26 = 44. 44/2 = 22, which is pretty close to what I'm getting.

[spacetoast]

Oh, I see now that I don't really understand how your machine works at all! I don't know what the epap and ipap mean. Can you explain them to me? Just for my own personal edification?

[Kiralynx]

Unless I am seeing large and lengthy leaks, I just "wing" it. I know what my 10 cm pressure vent rate is and I just look to see where I seemed to spend the majority of the time and allow for just a little more. Most of time time my overall average is right close to the normal vent rate for the 10 cm pressure. I figure it is just an average and unless I had a perfectly flat leak line I couldn't expect to come up with a figure unless I wanted to do a whole lot more math than I am inclined to do. I tend to look at the leak rate graph itself and it usually tells me a pretty good story. Obviously I don't have any experience with the fancier machines but this is how I look at my leak rate. It gets mostly a glance now.

OK, so then if one has an average IPAP of, say, 12, then one might figure around that figure +/- a few.

I generally glance at mine to see if it's reasonably flat, 'cause if it isn't, that's usually cause for figuring out what I was doing that wasn't quite right.

I don't stress over it, but if I crawl out of bed and am very achy or groggy, it's a reasonable bet that

a. I had a bunch of large leaks for whatever reason (rare except with a full face mask, if occuring with a nasal pillows mask, it usually means there was a dachshund on the straps)
b. I had a whole slough of hypopneas and periodic breathing that weren't caught for whatever reason
c. My average leak rate is significantly higher than usual, which probably means there was a dachshund lying on the mask straps during the night.

This is not critical, but it was something which suddenly occurred to me. And I wondered if others had wondered about it.

[Kiralynx]

Oh, I see now that I don't really understand how your machine works at all! I don't know what the epap and ipap mean. Can you explain them to me? Just for my own personal edification?

EPAP = exhalation pressure.

IPAP = inhalation pressure.

For more fancy commentary, see here:

viewtopic.php?p=359079#p359079

And yeah, the Bipap Auto SV has enough bells and whistles to drive anyone crazy, but it's proved ideal for me.

[spacetoast]

Ahhh. So the IPAP portion acts sort of like my auto? You can set a low and high pressure to take care of your events?

So, I would probably take your average IPAP from your data and use it to get the venting correlation and then average that with your EPAP value (18cm).

Thanks for the explanation!

[Pugsy]

I don't stress over it, but if I crawl out of bed and am very achy or groggy, it's a reasonable bet that

Yep, I sort of do the same thing minus the dog since my dog prefers to lay at my feet. I still haven't had but maybe a handful of "great" days in regards to how I feel despite having some "great" numbers. So with this in mind I just sort of make mental note of what might have caused things to be undermined a bit. I realize that I am still very new at this stuff and I also realize that I probably have experimented when I should have gone with the flow a little more.

Last night I did great until I woke at 3AM to let the dog go outside and clean up the mess he had made. Then I went back to bed (around 4 AM) and had a nasty little group of events which probably was around 5:30 AM and lasted about 30 minutes. Got up at 7 AM. That 3 hour period got scored all by itself since I was up about an hour. My AHI for that 3 hour period was 6.6 and all the events occurring during that 30 minute period. I looked at the graph for the leak and I see a larger leak than I would have wanted but I also see 18 cm of pressure. Hmmm. was the machine chasing the leak, was it chasing all those events, were the events happening because of the leak???
The events appear to have started before the leak. I am trialing the Opus 360 right now. Sometimes I do really good with it and sometimes I don't. The leak rate showed around 50 L/min during that 15-18 cm pressure time.
According to the paperwork at 15 cm the flow rate is 39 L/min and at 17 cm it is 42 L/min. So while at first glance the leak might appear quite large, at those pressures it really isn't a monumental huge leak.

Surprisingly, I felt quite decent today. I have had 2 nights in a row with 8 hours of sleep or more (even if broken up during the night) so that seems to play as big a part in my overall feeling as "great" numbers might play. It is still a struggle to get more than 6 1/2 hours of sleep with "great" numbers but I am slowly getting there.

So when I wake up feeling less than ideal, I also factor in the number of hours of sleep I got and did I remember tossing and turning a lot?? Most of the time the tossing and turning and shorter hours of sleep always go hand in hand. Just in case anyone thinks the increase in pressure wakes me and causes the tossing and turning. I don't think that is the case. The 18 cm nights are rare. Most of the time I might go to 12 -14 cm. I truly don't seem to notice the pressure increases and since I toss and turn on nights where the maximum hasn't need to go so high, I don't think that is a factor. I did experiment with a very narrow 2 cm window with the APAP. No change except that maximum of 12 cm let a truckload of events happen a couple of nights.

The numbers are there for me as sort of a validation but I think that they are only a very small part of the overall picture, so I also do not dwell on them.

[Kiralynx]

Yep, I sort of do the same thing minus the dog since my dog prefers to lay at my feet.

My two sleep anywhere they can squeeze in. Dunno if you were on the board yet when I had the adventure of the dachshund hose-warmer.

The numbers are there for me as sort of a validation but I think that they are only a very small part of the overall picture, so I also do not dwell on them.

Check -- I find, for instance, that I sleep lighter during the week. Part of this is because my husband is up and moving at 4:30am, and at that point, I've had just enough quality sleep that it is difficult to go back to real sleep.

But I like being able to check the numbers, because it tells me if something's gone really whacko. Like the last night of our vacation, I was using the full-face mask because of hay fever and woke up feeling as if I'd been beaten with an ugly stick. Checked the data and it seemed as if the whole night had been one giant large leak. Well, no WONDER I felt that way....!

[Kiralynx]

Ahhh. So the IPAP portion acts sort of like my auto? You can set a low and high pressure to take care of your events?

Basically, yes. I have the EPAP which handles the apneas, and then a range of IPAPs to handle other events and hypopneas. It's a pretty clever machine.

So, I would probably take your average IPAP from your data and use it to get the venting correlation and then average that with your EPAP value (18cm).

Thanks for the explanation!

Well, your idea seems logical to me. Wonder if anyone else will chime in on this.

Posting explanations is how we learn about this stuff. <g> If it weren't for the numerous posts by some of the truly brilliant people around here, I wouldn't be doing nearly as well as I am.

So... we pay forward....