A primer on looking at System One Leak lines

[robysue]

The following three images are all of my (excellent) leak line on August 9, my first night with the Bella Loops.

First, let's look at it in Encore Basic with the "leak to report" set at Unintentional Leaks:




This is easy to understand: A flat unintentional leak line with a barely visible bump meets anybody's definition of a great leak line.


If we set "leak to report" to Total Leaks in Encore Basic, we get an almost flat (a "fuzzy" flat) line right around 20 L/min, which is the expected leak rate for my min EPAP=4 setting. On this night, my EPAP = 4 for most of the night. The things to notice about this leak line is that it is mostly flat and in the neighborhood of my mask's intentional leak rate at the pressure I'm using.



Now let's look at the same leak line in Sleepy Head:graph itself is confined



The first thing that newbies notice about a Sleepy Head leak line is that it looks like the bumps are HUGE compared to those in Encore. But notice the scale on that vertical axis: Encore is plotting my leak data on a scale that goes from 0 L/min up to 140 L/min AND the graph takes up about the same physical "space" as the Sleepy Head graph. Sleepy Head, on the other hand plots my data using a vertical range of 10-30 L/min, and the graph itself is mainly between 16 L/min and 26 L/min. In other words, my leak data takes up only about 1/14 of the vertical distance in the Encore graphs, but it takes up 1/2 of the vertical distance in the Sleepy Head graph. That's why the bump looks so huge in Sleepy Head.

My own quick estimation of the "flatness" of the Sleepy Head graph is based on the vertical range off the data: If the leak data lies in a 10-15 L/min range in Sleepy Head, then the leak data will likely look flat or fuzzy flat in Encore. And if that
fuzzy" flat line is within +/- 5 or 6 L/min of the expected leak rate for the mask at your pressure, then the leak line is a pretty good to excellent leak line.

[JohnO]

If we set "leak to report" to Total Leaks in Encore Basic, we get an almost flat (a "fuzzy" flat) line right around 20 L/min, which is the expected leak rate for my min EPAP=4 setting. On this night, my EPAP = 4 for most of the night. The things to notice about this leak line is that it is mostly flat and in the neighborhood of my mask's intentional leak rate at the pressure I'm using.

How do you determine your mask's intentional leak rate at the pressure you are using?

I'm on week 1 with my PR System One auto, using a True Blue nasal mask, and trying to determine if my leak line is satisfactory. Sometimes if I switch from side to side, I'll feel a little air escaping. If I do, I can usually get it to stop by tapping the mask - with no more force than a person would adjust their eyeglasses.

[Tino2You]

From the Phillips instruction page (below) the intentional leak rates are 10 @2.2 cmH2O to 50 @ 30

http://www.healthcare.philips.com/pwc_h ... ForUse.pdf

[DoriC]

http://internetage.ws/cpapinfo/leak-rates-1.html

This might help if you can find your mask or a similar one listed.

[Sir NoddinOff]

A good thread: This info about leak lines is helpful in relieving the anxiety some people get when looking at their bumpy/jagged leak graphs. Besides all the newer machines easily adjust and adapt to moderate leaks, thereby maintaining excellent therapy. If it isn't doing that for some reason, it will show up on your machine's 'large leaks' reports.

[JohnO]

Great Info! Thanks!

[Starlette]

Awesome post Robysue a bookmarked keeper for sure!

Starlette

[Starlette]

Robysue,

This is another link you should add to your signature, just a thought.

Starlette

[GumbyCT]

A good thread: This info about leak lines is helpful in relieving the anxiety some people get when looking at their bumpy/jagged leak graphs. Besides all the newer machines easily adjust and adapt to moderate leaks, thereby maintaining excellent therapy. If it isn't doing that for some reason, it will show up on your machine's 'large leaks' reports.

NOT so...
the machine displays are rather lame at reporting excess leaks. Thus the importance of reviewing with software and the purpose of this thread.

I have had leaks off the charts yet the display showed 0 for leaks. I have no clue why - only that the LCD displays are NOT dependable.

Plus when using the software you can easily see if any events were caused during the leak period.

[Sir NoddinOff]

Edit: I forgot to mention that I usually 'zero out my machine data' on a daily basis... therefore it displays only that nights' collection. Sorry for the confusion

I totally disagree with you Gumby. I think the CPAP engineers have a firm grip on when the CPAP machine is failing to deliver therapy, via the built in sensors and circuitry. I think the LCD display, while not as graphically impressive as SH's colorful output, is reasonably accurate in telling the user when the device can't deliver adequate pressure to handle the apneas. That's a pretty easy software feedback loop to design and implement. Case in point. When I occasionally get a large leak, ie. my nasal pillows get dislodged, I find that it's so noisy and bothersome that I eventually wake up. Maybe it's just me, but I'm sensitive to those things. My PR S1 always catches and displays those instances on the LCD readout (I can't speak for the PR BiFlex), tho they admittedly are rare. As a side note, I don't take anything to interfere with my sleep, so that probably helps. (I"m not inferring that you do, so please don't take that wrong.)

[GumbyCT]

I totally disagree with you Gumby.

np you are entitled to. Get in line

I still contend that to find out if you are leaking you should (need to) check with the software for your machine to determine if the leak rate is within the manufacturers specs or NOT. IF your machine is a brick you may never know.

BUT you have to know your pressure AND the make & model of your mask. Your machine (mine anyway) does NOT know that

fwiw - I take nothing but 18cm to get to sleep
On the rare occasion that I can't get to sleep within 30 min or so, I take half a tab of melatonin and I'm done.

[lazer]

Thanks for the info! Still trying to determine if the below (from last night), is of any significance?

[Pugsy]

Thanks for the info! Still trying to determine if the below (from last night), is of any significance?

Did it wake you up?

[lazer]

Thanks for the info! Still trying to determine if the below (from last night), is of any significance?

Did it wake you up?

The one around 6AM did. Otherwise, for the main portion of last night, I do not recall awaking.

[robysue]

Lazer,

That 6AM wake is certainly significant since it woke you up. Did you have a dry mouth? Air blowing into your eyes?

The rest of the leaks are "ugly", but without seeing the rest of the data---the events, the wave form, and the pressure data, it's hard to say just how significant those other leaks are. Encore is not flagging them as "large leaks" and there's some small comfort in that.

Based on the "best" parts of this leak graph it looks like your typical "intentional leak" when the mask is well sealed is about 25 L/min. So if you were using a Resmed, "large leak" territory would start around 50 L/min, which is also about twice your apparent "expected leak rate" based on the graph. Now there's no particular reason to use the Resmed definition of "large leak" (unintentional leak rate >= 24 L/min) on a PR machine. But because I started off using a Resmed machine and because my PR BiPAP seems so reluctant to score any of my leaks as a "Large Leak", I've continued to use the Resmed definition as a rough, baseline guess of when a leak just might be large enough to affect my therapy. So if this were my leak line, I'd be a bit concerned if I were seeing a lot of leaks around the 50 L/min level both because 50 L/min is twice the expected leak rate and because of Resmed's identifiable definition of "large leak" since PR does not tell us what a large leak is. Most of your leaks are not that high (50 L/min), but some of them are beginning to get close to it.

So---if this were my leak data, how worried would I be about it? It depends. If this is an isolated night, I'd accuse Pugsy's aliens of paying a visit and shrug it off. If I had several nights like this in a row, I'd see if replacing my nasal pillows helped. If I frequently was seeing nights like this in spite of using new pillows, I'd start wondering if there was something going on---such as mouth breathing---particularly if I was also having serious problems with dry mouth OR if the rest of the data were indicating there might be some compromise in the quality of my therapy.