What is large leak threshold for various cpap's?

It seems 24 lpm is the threshold for Resmed from what I've seen. Wondering what they are for other brands and if different why is that?

They are different because they report leak differently.
ResMed subtracts a generic value for the vent rate per the mask setting and reports excess leak only and they came up with 24 L/min.

Other brands of machines report total leak which is the intentional vent/leak rate plus any excess leak.
Vent rates increase as the pressure increase and when auto adjusting pressures are used the line in the sand for excess leaks will vary both from the mask used and the pressure so it's difficult to come up with an exact number for the large leak threshold because it can vary so much.

In general...F & P Icon will have a 60 L/min approx...line in the sand.. when total leak is reported. Their older SleepStyle machines had the line in the sand up around 90 to 100 L/min.

Devilbiss used to have around 90 L/min...I haven't seen anything in a long time though. I got that from reading through their software use guide...that's total leak also.

Respironics again uses total leak and large leak line in the sand will vary a lot but usually somewhere between 75 and 90 L/min depending on the mask and the pressures used and maybe even a little higher when a full face mask is used with pressures around 20 cm.

Resmed is the only one that reports excess only leak and I think the 24 L/min line in the sand is a bit conservative.
I never get a large leak flag with a Respironics machine and I rarely don't have at least one little kiss with large leak territory with my ResMed machine. I think there is some wiggle room with the ResMeds in terms of where the leak really can significantly impact therapy and recording ability. It doesn't go immediately in the toilet at 25 L/min but instead becomes more iffy the farther above 24 that a person goes. Over 30 L/min and we start seeing some unknown flags which means the machine is having trouble deciding what the event was. Over 35 L/min and all bets are off as I have seen it miss flagging events right after a 32 L/min leak giving me an "unknown" flag.
So over 35 L/min and the machine is pretty much clueless.

Thanks for your reply. I find this interesting. The reason I wanted a comparison is I'm using an Apex Auto XT and there is little documentation on leaks etc. Initially I thought my leaks were high, and probably in the beginning as i was getting used to a new mask and machine they were. Nobody seems to know what the large leak area is on this cpap. The zzzPap which was the same cpap with a different name had a red line at 70 on their graph. No red line on the new software. Otherwise the machines are identical except for the brand name change.

However, I did a test using a Wizard 210 nasal mask and a Profile Lite Gel sitting in a chair and making sure my mouth was closed and the mask wasn't leaking. The Wizard at 8 cmH20 has an exhaust rate of about 24-25 lpm. The Profile lite at 8 cmH20 has an exhaust rate of about 20. I did the test for 45 minutes at around 8-9 cmH20 knowing that the machine does not start recording data for the first 20 minutes to let a person get situated in bed. It turned out the results were about 54-56 lpm leak for both masks.

I am now assuming that the red line at 70 lpm on the previous software would be were the large leaks start. As it is my average leak rate for about 2 months of therapy is 55.4. My average AHI is 2.3. My average time with large leak is 3.1 minutes. Of course there at times when my lpm spike here and there and there are times my AHI is higher and times where the average time with large leak is higher. I think one day my highest AHI was around 6.

Judging from this I am thinking i am doing quite well with my therapy. And I am thinking that 10-15 lpm over my baseline of 55 from the test, or even maybe 20 lpm is ok. The times it spikes above that are here and there and I understand that this type of thing is pretty much normal.

Would you agree with my assessment?

Sounds like a reasonable assessment to me.

I never really worried too much about the actual line in the sand. I just looked to see what the machine said about the time in large leak and if it wasn't very much I shrugged my shoulders and moved on. Random brief spikes are probably mask movement leaks and not big deal.
I only started worrying when I would see prolonged periods of time in large leak...like 30 to 60 minutes at a time on a consistent basis.

Thanx Pugsy. I agree with you. I know a couple times it showed I had large leaks for 25 minutes and once for 45 minutes. This is pretty rare though and probably a night where I was dead tired.

With the numbers I'm getting I am also assuming it is not worth it for me to try to improve the leaks with a chin strap or FFM, unless I've got a stuffy nose and might need to do some mouth breathing. Wouldn't you agree?

I would avoid a chin strap or full face mask at all costs.
No way would I go to extraordinary measures to fix maybe 10 minutes of maybe mouth breathing maybe 1 night a week that I sleep right through anyway.
Been there and done that and the cure is worse than the disease for me.

Any leak, even tiny, that wakes us up needs to be worked on from the sleep quality standpoint of things.
Leaks that don't wake me up...I look to see how far into large leak territory I went and how long was I there and is it something that happens often or rare.
Then I decide if I need to do anything special about it.

A while back I had occasion to look closely at the leaks. Was spending 20 to 30% of the night in large leak territory and they were waking me up....3 nights in a row. Tried a new nasal pillow and it didn't help. So then I got new headgear and that fixed the issue. My headgear was all stretched out and no amount of hot water washing would shrink it up enough.

Thank you Pugsy. It's a relief getting such good comments from you and that they agree what I've come up with after over 2 months of very tedious research. I'll put you in for a promotion and a raise

Well,

For leaks in tubing you can feel with hand. More couplings = more leaks. Hose does deteriorate, the plastic between wire coils breaks.

There shouldn't be any leak from the interface, though that is difficult to achieve. Keep pressure on your provider to get you a proper interface that is stable.

Perhaps size of exhalation vent varies.

As for calibrating machine to a leak rate, I ask if there really is much px drop from machine to interface with typical flow rates.

There is enough pressure drop in the hose that the manufacturers want to know what hose you are using!

WickedLoki wrote:There is enough pressure drop in the hose that the manufacturers want to know what hose you are using!

indeed, I've measured over 9cm pressure drop between the machine and and mask with a 3 meter hose and antibacterial filter.

just over 27 at the machine, 18 (which was programmed) at the mask.

Ouch, that's a big drop - how much is due to the antibacterial filter?

Why is the filter on the output of the machine not on the inlet?

BigNortherner wrote:Ouch, that's a big drop - how much is due to the antibacterial filter?

surprisingly less than you'd think, but I don't have the numbers in front of me. the 10 feet of hose has more flow resistance than the 3.97 square inches of filter material.

BigNortherner wrote:Why is the filter on the output of the machine not on the inlet?

because it's designed that way.