Leak Rate Graph

The Leak Rate graph---a detailed look

Depending on what machine you are using, the Leak Rate Graph will have either one or two graphs in it.

ResMed machines report only the excess leak rate, which is simply called Leak in the OSCAR leak data. A ResMed user will see only one leak graph in the Leak Rate graph.

All other major brands of data-capable CPAPs report Total Leaks, which include both the intentional leak rate for your mask at your pressure AND the excess leaks. In other words:

Total Leak = Intentional Leak + Excess Leak

OSCAR does a statistical analysis of the Total Leak data for non-ResMed machines to calculate an estimated excess leak rate and reports this estimated excess leak as Leak Rate. This means that users of NON-ResMed machines have two "leak" graphs in the Daily Detailed Data graphs: One for Total Leak (the raw data from the machine) and one for Leak (the OSCAR estimated excess leak rate).

The top (gold) graph is the Total Leak Rate graph and the bottom (purple) graph is the Leak Rate graph, which shows the OSCAR estimated excess leak rate.

Defining Large Leaks

Different manufacturers have different definitions of what Large Leak means for their machine. But for all brands of machines, the idea is that if your leaks are under the manufacturers' Large Leak definition, the machine should be able to gracefully compensate for the leaks and deliver effective therapy and accurate data.

Per PR DreamMapper Help FAQ What is a large leak?

Philips CPAPs tolerate up to twice the intentional leaks. They compensate for this leak by adjusting the speed of the blower. Beyond the tolerance threshold, the DreamStation indicates that its detection is not reliable in terms of the increased level of non-intentional leaks. It then qualifies these leaks as large.

Intentional Leak Info is derived from Intentional-leak-rates-for-DreamWear-masks-and-exhalation-ports.pdf

The conservative approach to identifying a Large Leak on Philips Respironics machines is to Manage leaks that exceed the minimum Large Leak line in the above data.

Information about how ResMed, Philips Respironics, Fisher & Paykel and DeVilbiss each define Large Leak can be found in 8. Leaks.

Part II: Are my leaks bad enough to worry about?

Interpreting the graphical leak data

The Leak Rate graph is the most reliable way of answering the question: Are my leaks both large enough and LONG enough to adversely affect the quality of my therapy and the accuracy of my data?

Loosely, Leak and Total Leak lines can be described as "Great", "Good", "Decent Enough", "Problematic", "Bad", and "Horrible", all of which are based on the amount of time the leaks or total leaks are in Large Leak territory for your particular machine.

Great, Good, and Decent Enough Leak/Total Leak lines

In general, a Great Total Leak line will be flat or almost flat and hover somewhere around (or just below) the intentional leak rate for your mask at your pressure. A Good Total Leak line will be "fuzzy" flat, stay mostly around the intentional leak rate for your mask and pressure, but tends to have some visible periods of noticeably higher leaks, most of which stay well below the cut off for "Large Leaks" for the given machine. A Decent Enough Total Leak line has more obvious leaks than a "Good" one does, but line stays below the Large Leak line for at least 70-90% of the night. (There's some debate between CPAP users of just how long the Large Leaks need to last before they become problematic.)

For ResMed users or for folks who simply want to concentrate on the (excessive) Leak data, a Great Leak line will be flat or almost flat and hover somewhere around (or just below) 0.0 L/min. A Good Leak line will be "fuzzy" flat, stay mostly around 0.0 L/min, but tends to have some visible periods of noticeably higher leaks, most of which stay below 10-15 L/min. A Decent Enough Leak line has more obvious leaks than a "Good" one does, but the line stays below 25-30 L/min for at least 80-90% of the night. (There's some debate between CPAP users of just how long the Large Leaks need to last before they become problematic.)

If we look at the Statistical Leak data from the Left Side bar for Great Leak/Total Leak lines and Good Leak/Total Leak lines, the 90% (or 95%) Leak/Total numbers will be under the manufacturer's definition of "Large Leak". The maximum may or may not be under that line.

The Statistical Leak data for a Decent Enough Leak/Total Leak line will have a median Leak/Total Leak number well below the the manufacturer's definition of "Large Leak". The 90% (or 95%) leak numbers, however, may very well be larger than the official Large Leak definition.

Problematic Leak/Total Leak Lines

These are leak lines where it's clear that Large Leaks are present during a significant amount of the night, but it's not clear if the Large Leaks last long enough for the machine's manufacturer to say they are a problem.

The manufacturer with the clearest definition of when Large Leaks become long enough to adversely affect the quality of the CPAP therapy and the accuracy of the data is ResMed: ResMed indicates on the machine's Sleep Quality Report when the (excess) Leaks are AT or ABOVE 24 L/min for at least 30% of the night. So we'll assume that if the time in Large Leak is approaching 30% of the entire night, the Large Leaks are problematic.

So a good working notion for a Problematic Leak/Total Leak line would be the following:

A Problematic Total Leak line is one that is NEAR or IN the manufacturer's Large Leak Territory for somewhere between 20-35% of the night; A Problematic Leak line is one that is ABOVE 24 L/min for somewhere between 20-35% of the night. A Problematic Leak/Total Leak line indicates that the leaks may be both long enough and large enough to have an adverse effect on the quality of your therapy and the accuracy of the data.

The Statistical Leak data for a Problematic Leak/Total Leak line will typically have a median Leak/Total Leak number well below the manufacturer's definition of "Large Leak", but the 90% (or 95%) leak numbers, will be larger than the official Large Leak definition.

If you see a Problematic Leak/Total Leak line every now and then, there's no point in worrying about it. If you see Problematic Leak/Total Leak lines a lot, however, you may want to consider taking measures to address the leak issues.

Bad and Horrible Leak/Total Leak Lines

These are leak lines where it's clear that Large Leaks are present during a substantial amount of the night, and it's clear the Large Leaks are both long enough and large enough to adversely affect your CPAP therapy.

A working definition of a Bad Leak/Total Leak line is that the leaks are bad enough to trigger an unfavorable leak indication if you were using a ResMed S9: If large leaks make up more than 30% of night, you've got a problem with leaks.

A Horrible Leak/Total Leak line is a leak line where the leaks are totally out of control: If over 50-60% of the night is in Large Leak territory, you've got a Horrible Leak/Total Leak line and a pretty significant problem with leaks.

The Statistical Leak data for a Bad Leak/Total Leak lines may have a median Leak/Total Leak number well below the manufacturer's definition of "Large Leak", but the 90% (or 95%) leak numbers, will be larger than the official Large Leak definition. If the median Leak/Total Leak number is close to or above the manufacturer's definition of "Large Leak", then you've got a Horrible Leak/Total Leak line.

Most people don't have random, rare Bad or Horrible Leak/Total Leak lines. Folks who have real leak problems tend to have Bad or Horrible Leak lines on a significant portion of the nights they use the CPAP. If you are seeing multiple Bad or Horrible Leak/Total Leak lines each week, you know you need to do something about the leaks.

A final comment on the connection between the Statistical Leak data and the graphical leak data

It is important to note that Decent Enough, Problematic, and Bad Leak/Total Leak lines may all have the same characteristics in the statistical Leak data:

• The median Leak/Total Leak numbers will be well under the manufacturer's official definition of Large Leak
• The 90% or 95% Leak/Total Leak numbers will typically be above the manufacturer's official definition of Large Leak.

What separates Decent Enough leaks that you don't need to worry about from Bad leaks that must be fixed is the duration of the large leaks. And knowing the median and 90% leak/total leak rates is just not enough information to tell whether the large leaks lasted about 10-15% of the night (Decent Enough) or whether the large leaks lasted about 40-45% of the night (Bad or Horrible).

If the median Leak/Total Leak numbers look good and the 90% (95%) Leak/Total Leak numbers are in Large Leak territory, you must look at the Leak/Total Leak graphs in order to figure out whether the leaks were both long enough an large enough to adversely affect your therapy.

Donate to Apnea Board