Can you explain leaks?

[MoonBear]

Hi,

Thanks to help here, I have finally been able to load my S9 Elite. The great news is since the 8th, my average AHI is under 1.

I do not understand the leak numbers and their significance. It seems obvious that lower is better, but what constitutes a high or low reading is a mystery. I have been trying all kinds of things to keep my Quattro from hurting my nose and abrading skin, and suspect some leaks may be happening due to this. I do see it is liters per minute, but I don't, again, understand how many lost liters would be considered good or bad.

So here are my numbers for the past seven days. could someone tell me if these leaks are of concern? If you have leaks, but your AHI is below 1, is the leaking still a problem? What does 95th percentile indicate?

Date. Median. 95th Percentile. Maximum

12/29. O. 10.8 24
12/28. 0. 1.2. 4.8
12/27. 0. 3.6. 152.4
12/26. 0. 10.8. 16.8
12/25. 0. 6. 163
12/24. 0. 2.4. 72
12/23. 2.4. 16.8. 22.8
12/22. 0. 6. 10.8

Some days I take off my mask without turning off the machine. Won't do that anymore.

It would seem that leaks are irrelevant if my ahi is under 1? Even if these numbers indicate significant leaks (so hard to believe as I feel like my face is vacuum-sealed under my quattro when I am awake), if my AHIs are under 1, isn't that what is most important? Or am I missing something?

THANKS FOR THE HELP! I do appreciate it. ANd BTW, there are leaks showing in the first few days before any skin was
irritated and the seal was perfect. For example, therre is a day with .1 apnea, .o hypopnea with an apnea average of .1, and leak median of 4.8' , 95th percentile of 16.8, and a maximum of 21.6 .

Thanks again.

Namaste,
MoonBear

[Muse-Inc]

...Median...95th Percentile...Maximum....

Median means that 50% of the night the leak was below this number and 50% above.
95thcentile means that 95% of the night leak was below or equal to this number.
Maximum means the highest leak the machine recorded that night.

For the pressure readings, just substitute pressure where you see leak in the above definitions. Max is the max pressure the machine delivered that sleep session.

For some an AHI <1 would be heaven! Yes, it's a good number and many here would give almost anything to be able to reach that number. AHI is about the number of events whereas leak is about therapy air escaping from the mask and your airway. Until the leak reaches the red line shown in the detailed graphs (can't remember the exact number right now), the machine can compensate and will increase pressure to keep your aiways inflated (open). The larger the leak the higher the APAP will increase the pressure (to compensate for the lost therapy air) which is why you want to keep leak low...the APAP will increase pressure until leak reaches that red line at which point the machine cannot fully inflate your airways as needed.

I hope this helps Moonbear.

[KatieW]

wiki/index.php/Mask_Leaks

[robysue]

MoonBear,

First, before I get to the tutorial, those leak numbers look pretty good. The short version of the tutorial has been provided by Muse and KaiteW. But if you want a more step-by-step version, here it is, complete with your numbers for the examples.

First the basic definitions:

• The median leak rate is the rate that you were leaking AT or BELOW for 50% of the time the machine was running for the night. That also means you were leaking AT or ABOVE this rate for 50% of time the machine was running for the night.
  
  The 95% leak rate is the rate that you were leaking AT or BELOW for 95% of the time the machine was running for the night. This is the number that is shown on the machine's LCD each morning. That also means you were leaking AT or ABOVE this rate for 5% of the time the machine was running for the night. To get an idea of how long 5% of the night is, the key is to remember that 5% of one hour is equal to three minutes. So you can multiply the usage time on the LCD (which is shown in HOURS) by three minutes to get an idea of how long you were leaking at a rate AT or ABOVE the 95% leak rate.
  
  The maximum leak rate is the largest leak rate the S9 detected during the night. Note that the S9 samples the leak rate several times a minute, but not continuously. Of the three leak rates, this one is probably the least useful to most people since it can be very high if the S9 samples the leak rate just as you break the seal to do some serious scratching of the top of your nose for example.
  
  Now lets look at those numbers you provided.

  Date. Median. 95th Percentile. Maximum
  
  12/29. O. 10.8 24
  12/28. 0. 1.2. 4.8
  12/27. 0. 3.6. 152.4
  12/26. 0. 10.8. 16.8
  12/25. 0. 6. 163
  12/24. 0. 2.4. 72
  12/23. 2.4. 16.8. 22.8
  12/22. 0. 6. 10.8
  
  Some days I take off my mask without turning off the machine. Won't do that anymore.

  Bet the days you took the mask off without turning it off were 12/17, 12/25, and maybe 12/24. It won't harm anything and I wouldn't worry about it if you do it again. As I said, those max leaks don't really mean that much. The 95% leak is much more important as we'll see in just a minute.
  
  Now on every night except 12/23 your median leak was 0.0. That means on all but one night, you had no detectable unintentional leak for half the time the S9 was running. That's reall, really good for someone just starting out. Give yourself a pat on the back. And on 12/23, you were leaking at a rate that was LESS THAN or AT 2.4 L/min, which is well less than the red line in ResScan (which is at 24 L/min). That's an acceptably low median leak rate from ResMed's engineers point of view (since you saw Mr. Green Smiley on the next morning.) Now, is it acceptable to you? Well, if the small leaks that night didn't keep you up and bother you, then my advice is you can ignore them.
  
  Now let's examine those 95% leak figures a bit more closely. Most of them are well less than 10. Again---if you don't remember fighting any leaks on those nights, these 95% leak figures are so small that you don't need to worry about the leaks. After all, remember that you were leaking at a rate ABOVE these tiny leak numbers for an average of THREE MINUTES per HOUR.
  
  Now three of your 95% leak figures are what I call "middling" 95% leak rates. They are still quite low---far too low to make Mr. Red Frowny Face show up. But they are just large enough that there is a chance the leaks that caused them may have also caused some discomfort to you and hence disruption in your sleep. My own feeling about middling 95% leak rates is this: If I don't remember any leaks waking me up and bothering me and demanding my attention, then I don't worry about them. But if I do remember fighting leaks for any part of the night, then I do try to figure out what's going on leak wise and address the issue.
  

  It would seem that leaks are irrelevant if my ahi is under 1? Even if these numbers indicate significant leaks (so hard to believe as I feel like my face is vacuum-sealed under my quattro when I am awake), if my AHIs are under 1, isn't that what is most important? Or am I missing something?

  There are two kinds of BAD leaks in my opinion:
  
  • Leaks that are bad enough to compromise your therapy. Your leaks are NOT this kind. With the S9, it's easy to tell if your leaks are this bad: Mr. Red Frowny Face shows up. If you start seeing extended leaks in ResScan above the red line (24 L/min), those may also indicate your therapy might be beginning to be compromised. But a really short spike above the Red Line is not something you need to worry too much about in my opinion.
    
    Leaks that are bad enough to compromise your comfort and hence your sleep quality---regardless of how small they are. If a leak is keeping you awake or if a leak is waking you up and keeping you from getting back to sleep, it's a problem that has to be addressed. It doesn't matter how tiny it is---if the leak is bugging you, you need to figure out how to fix it.

Now your current leaks clearly don't fit into the first category. Only you can tell whether they fall into the second category. But if they don't fit into the second, then I think you don't need to worry about leaks right now.

[MoonBear]

Another greeat explanation, Robysue. Thankfully, I haven't had any chronic leak issues. So if I can figure out how to keep my mask Zest from hurting my nose -- and causing skin abrasions --I will be in bliss. But even with these things, I am so grateful to now understand leaks and how to regard them. Once again, another post for the archives.

Bear Hugs,
MoonBear

[jules]

was that data you posted with the quattro (mask on your profile) or with the zest (mask you mention)?

[jbenenson]

BTW there is a misunderstanding about the term "median". It's another way of saying "average", determined by adding up all the data and dividing it by the hours, but it doesn't mean that 50% of the time the data were below the median and 50% above. That's the "mean". For example, if you had one huge occurrence, say 20 at the end of the night (1 hour) and 2 the rest of the time (9 hours), the median would be 3.8 and the mean would be 2. The ResMed S9 reports the median not the 50% value (if they know the difference).

[jules]

BTW there is a misunderstanding about the term "median". It's another way of saying "average", determined by adding up all the data and dividing it by the hours, but it doesn't mean that 50% of the time the data were below the median and 50% above. That's the "mean". For example, if you had one huge occurrence, say 20 at the end of the night (1 hour) and 2 the rest of the time (9 hours), the median would be 3.8 and the mean would be 2. The ResMed S9 reports the median not the 50% value (if they know the difference).

I think you need to go back and relearn your basic stat material.

[avi123]

Comment:

Most CPAP machines do not use a sensor to measure the pressure inside the mask. So how could they estimate mask leak accurately? If I am correct that you can't accurately estimate the mask leak during treatment, without taking a measurement at the mask, then all those fency statistical data are sort of for the birds?

Recent patents applications by Resmed do talk about pressure sensors in the masks. This in addition to flow sensors at the blower outlet. Such arrangements would require either electrical wires or pneumatic tubing going from the mask to the CPAP controller.

Latest machines by Resmed do offer a Mask Fit feature whereby a 3 minutes static cycle is devoted to mask leak testing. But it seems that nothing yet on the mask pressure sensors for monitoring the leaks over time.

Puritan Bennet GoodKnight® 420E Auto-CPAP System does offer pressure measurement at the mask, "for a precise measurement and better patients comfort". See such an air hose with an inner pressure sensing tubing:

http://www.cpapxchange.com/cpap-tubing- ... bipap.html