Leak Rate and AHI

[clownbell]

@Dave - thanks for the thought but it was 108 here today. Should have been ICED coffee but i tanked up on regular old H20 instead.  

[multicast]

The intended leak (which is not shown in ResMad's machines) is much more than 24; roughly double it. And the unintentional leak is sort of oraculated by all machines.

[Ratchick]

My understanding is this but I stand to be corrected.

The leak graph shown in ResMed is equivalent to the unintentional (lower) leak line on the Philips. Both of those show leaks AFTER taking into account the expected leak that is built into the mask. This figure will vary depending on the mask and the pressure being used (the higher the pressure, the bigger the intended leak). The figures should be listed in the manual for your masks (and can be altered in the OSCAR settings if needed).

In Resmed data, the intended leak figure isn't shown on any graph. In Philips data, you have the Total Leak Rate (which is the intended leak rate plus the unintended leak rate) as well as the unintended Leak Rate as another (lower) line on the graph. The 24l/min figure is not the intended leak rate - it's the point at which unintended leaks (after taking into account the intended leaks) are high enough that the Resmed may start to have issues reliably counteracting them. The 24l/min has just generally been accepted as a boundary at which leaks become an immediate problem.

So if the mask at a specific pressure expects you to have a 50l/min intended leak, and the actual leaks are measured at 55l/min, In OSCAR for data from a Resmed, you would have one line showing a value of 5 for leaks, and with data from a Philips, you would have a Total Leak line showing 55 and a lower, unintended Leak line showing 5.

You can demonstrate this by making sure your mask isn't leaking at all - and you'll still feel air escaping from the vent. Those are the intended leaks that Resmed doesn't show, but can be calculated on the Philips by comparing the two lines on the graph.

In reality, the Resmed can supposedly cope with about double that, but ideally, you probably get better therapy and more restful sleep with fewer unintentional leaks. This should reduce your AHI more effectively, and also ensure that the machine is better able to monitor your breathing and counter issues that might potentially be missed with a lot of high leaks.

[Islander99]

Many thanks for everyone's responses and they have helped in my understanding of the numbers. You are correct in noting that what matters most is how one feels under the influence of CPAP. My AHI last night, for example, was 1.01; 29 seconds in apnea; and 0% over leak redline. My leak rate was Min 0; Med 1.2; 95% 10.8; and Max 13.2. Today, I feel fine/refreshed after last night's sleep. No question that I do breathe through my mouth on occasion through the night although I am wearing a nasal mask.


Correct me if I am wrong in my thinking but take a subject with 0 apnea and let's say that he's a mouth breather and his leak rate is therefore 100 percent. For that person, the leak rate wouldn't matter because CPAP therapy would be unnecessary. For those with sleep apnea, leaks become important if they occur during an apnea event or an apnea event occurs because the pressure needed to prevent same is lacking (i.e., leaking and apnea events occuring at the same time).


In future, I will be less concerned about leak rate and more concerned about how I feel the next day.

[Ratchick]

My understanding is that if someone has to breathe through their mouth at night, they can still have apnea. It's not just breathing through your nose that causes the obstructive events.

If you're having some minimal mouth leaks, and otherwise feeling fine (especially with no time over the redline - which is the 24l/min figure) and an average leak of 1.2l/min, you might be fine to just leave it, as is. Otherwise, if they are mouth leaks, you could go ahead and try various "fixes" for those, but as others have said - if you're feeling amazing, you may choose not to bother. While zero unintentional leaks might be ideal, it's probably not achievable for even the majority of people.

[SarcasticDave94]

Yep, I'm a heavy percentage mouth breather. This doesn't eliminate the likeliness of Apnea. I still have both Obstructive, Hypopnea, and Central events. I use a full face though. Leaks still count though.