SaxChick wrote:Does "Maximum: 18.0" mean "the largest leak was 18 liters per minute" or that I had 18 leaks per minute at one point, or something else?
First, the leak rate is best thought of as a measure of
How much air is leaving the system each minute? Note that "the system" is the PAP machine, the hose, the mask, and your upper airway. On the Resmeds, the
unintentional leak rate is reported---in other words, the figures are reporting
How much air is leaving the system above and beyond the expected, intentional leak rate for the mask?.
Next,
How much air? means we're talking about the
volume of air. And you can think of a ``liter'' of air as the air that fills an empty one-liter bottle. It's basically a quart of air.
So an unintentional leak rate of 18.0 L/m means that the system is losing 18 Liters of air per each minute the machine is running.
Now for the stats lesson you've forgotten.
Your leak numbers are: Median: 0.0, 95th% 15.6 and Maximum 18.0
What do these numbers mean?
Median: 0.0
This means that for 50% of the time the S9 was running, your unintentional leak rate was AT or BELOW 0.0 L/min. In other words, for at least 50% of the night, the S9 could detect no
unintentional leaking. It also means that your unintentional leak rate was AT or ABOVE 0.0 L/min for 50% was running. If these are overnight figures, that's 50% of the night with leaks AT or BELOW 0.0 L/min and 50% of the night AT or ABOVE 0.0 L/min.
95%: 15.6
This means that for 95% of the time the S9 was running, your unintentional leak rate was AT or BELOW 15.6 L/min. It also means that your unintentional leak rate was AT or ABOVE 15.6 L/min for 5% was running. If these are overnight figures, that's 95% of the night with leaks AT or BELOW 15.6 L/min and 5% of the night AT or ABOVE 15.6 L/min. And how much is 5% of the night? Well, 5% of one hour is
three minutes. So you can get an idea of an upper bound on how long your worst leaks (the ones above the 95% leak figure) lasted by multiplying the usage (in hours) by three minutes/hour. For example, if your machine was running for 7.3 hours and the 95% leak figure is 15.6, that means your leak rate was AT or ABOVE 15.6 L/min for a total of
(7.3 hours)*(3 minutes/hour) = 21.9 minutes
Maximum: 18.0
This means that at some point when your S9 was sampling the leak rate it detected a leak of 18.0 L/in. We know you could not have been leaking at this rate for more than 5% of the night because your 95% is much lower than 18.0. When the max leak rate is this much higher than the 95% leak rate it could simply be that the S9 happened to sample the leak rate just as you were making a major adjustment to the mask and you knew the seal was broken because you'd pulled the mask away from your nose in order to reseat the mask. Or it could be that you had a 15 minute leak that was really, really bad. Only the leak line tells which case is more likely.
Are your leaks really a problem?
Leaks come in three basic varieties:
- Leaks that are LARGE enough and LONG enough to adversely affect your therapy. These obviously have to be dealt with. Are your leaks in this category? Well, the Resmed engineers believe the machine is capable of compensating for leaks up to 24 L/min as long as they're not too long lasting. The infamous Mr. Red Frowny Face shows up when the Resmed engineers believe your leaks are both LARGE enough and LONG enough to compromise both your therapy and the data the machine records. Mr. Red Frowny Face shows up when the 70% leak rate is AT or ABOVE 24 L/min. In other words, the Resmed engineers believe that if the leak rate is AT or ABOVE 24 L/min for 30% (or more) of the night, there's a real leak problem that the machine cannot cope with. And at that point, something needs to be done to address the leaks. In your case, the leaks are not bad enough to be triggering Mr. Red Frowny Face.
- Leaks that are LARGE enough and/or LONG enough to adversely affect your comfort. These are leaks that are either not large enough or not long enough to clearly adversely affect your therapy and the data. But if a leak wakes you up, it's a problem. If you wake up with dry eyes from leaks causing air to blow in your eyes, that's a problem. If you wake up with a dry mouth, that's a problem. If you can't get to sleep in the first place because every time you move in bed the mask springs another leak that makes you more alert, that's a problem. And if you can't get to sleep because the leaks simply annoy you and keep you from drifting off into slumberland, that's a problem. In other words, if the leaks are causing you discomfort, they're a problem and they need to be dealt with so that you'll be more comfortable, and hence, sleep better.
- Leaks that are NOT large enough and/or long enough to adversely affect your therapy AND do NOT cause you any discomfort. My advice on these leaks is to not lose sleep over them. No one is going to have 95% leak rates equal to 0.0 L/min night after night after night. If that 95% leak rate is below 10 or 15 and you're sleeping through the leaks and not waking up with any problems caused by the leaks, then don't get too worried about working excessively hard to eliminate the last bit of leaking.
