How to determine acceptable Leak rate?

[erik67]

I've been a (mostly) successful CPAP user for over 5 years , and one question that has always puzzled me is how do you determine an acceptable leak rate? I seem to think that it has something to do with the mask itself, but in searching the message boards I am seeing people quoting some much lower leak rates than I am seeing with my machine (sometimes as high as 75 lpm, but mostly below 50 lpm).

Any suggestions on how to determine this?

Thanks!

[BleepingBeauty]

I've been a (mostly) successful CPAP user for over 5 years , and one question that has always puzzled me is how do you determine an acceptable leak rate? I seem to think that it has something to do with the mask itself, but in searching the message boards I am seeing people quoting some much lower leak rates than I am seeing with my machine (sometimes as high as 75 lpm, but mostly below 50 lpm).

Any suggestions on how to determine this?

Thanks!

Hi, erik.

The mask booklet features an Intentional Vent Rate chart. Find the chart, and determine what the intentional leak rate is for your mask at your pressure setting(s). Then compare it against the reported leak on the machine.

Hope that helps.

[KatieW]

You will read ResMed users report a 0 (zero) leak rate. That's because Resmed has a mask setting feature, where you can input your mask type, so it calculates your actual leak rate.

[erik67]

Thanks to both of you! That helps a lot.

[OutaSync]

Erik,

If you can't find your chart, you can post your mask type and pressure rate and someone can help you get the intentional leak rate of your mask. Anything over that number will be your real leak rate.

Bev

[erik67]

Given my mask (Mirage LT) and my pressure range of 6-10, anything under 30 lpm is very good, based on the Resmed brochure. So I think that based on my leak rates, I need to tighten up the mask a little bit.

[OutaSync]

Or you may need to plug up the hole directly below where your mask sits. Seriously, the mask may not be leaking and tightening it may not help. You could be leaking air out of your mouth. That too, will cause high leak numbers.

[erik67]

That's a really good point. So here's a dumb question - how do you know if you're mouth leaking?

[OutaSync]

For me, I tried taping my mouth and saw my leak line straighten right out. Proof enough. Plus, when the air comes out of my mouth, it wakes me up. I'm a "light" sleeper, so everything wakes me up.

[Craig P]

Your mouth may be dry due to the airflow.

[jules]

if you have the software look at the leak graphs - are they flat or are there many hills and valleys?

[OutaSync]

if you have the software look at the leak graphs - are they flat or are there many hills and valleys?

He has the software, Jules, but it doesn't tell him where the leaks are coming from.

[erik67]

The Encore Pro software does give me leak rate data over the course of the night - I know that when I look at the daily max leak rate with the encore pro analyzer software that the leak rate varies from day to day, but not sure what that means. Would "peaks and valleys" or a straight line be more indicative of mouth breathing? I'll check when I'm home tonight and post again.

BTW, the only time I wake up with a dry mouth is when I 1) don't use CPAP at all and 2) when the humidifier runs out of water.

Thanks all for your input!

[jules]

if you have the software look at the leak graphs - are they flat or are there many hills and valleys?

He has the software, Jules, but it doesn't tell him where the leaks are coming from.

I realize it doesn't say where but one then has to start looking to see.

You want the graph to be fairly flat - it will rise when pressure goes up sometimes so perfectly flat isn't going to happen. You don't want to see a lot of big up down steps - some jagged one step up and down can be fine.

Take the graph and draw a line across at say 30 or so and see how much of the time is spent above that line. Then start trying to figure it out - are there other signs of mouth breathing ? are the pillows still intact each time you wake up or do you have to readjust them? is there a leak anywhere else in the circuit (use paper tape or teflon tape on any joints to seal them - check the hose for leaks too)

[OutaSync]

The max leak rate doesn't really mean much to me. That will show up as sudden rises when I pull my mask away from my face to reseat the cushion, or if I have to reach under to scratch an itch. The average leak rate is more of what is happening during the night.