How important is leak rate?

SleepySandy · Post by **SleepySandy** » Wed Jan 31, 2007 11:28 pm

I just got my EncorePro software and I'm still kind of confused about the importance of the leak rate.

I currently use a CL2 with the simple mask. My pressure is 10. I was able to find the vent flow rate for my setup is 28.

Last night my AHI was 0.5 but my leak rate is 43.91.

If my AHI is really low, does the leak rate really matter?

Rabid1 · Post by **Rabid1** » Wed Jan 31, 2007 11:31 pm

Don't mess with that kind of success! Leak rates are an average, and if you had a major leak it would factor into that.

CollegeGirl · Post by **CollegeGirl** » Thu Feb 01, 2007 12:23 am

The important question is, did you have any periods of Large Leak (LL)? If so, AHI is not recorded during that time, and so would have corrupted your AHI data for that night.

oldgearhead · Post by **oldgearhead** » Thu Feb 01, 2007 9:53 am

I think 43 LPM at 10 cm/H2O would be a low to moderate leak for the
CL2. I am not sure if the machine's ability to detect events would be
compromised with that amount of leak. But you probably need to fix it.

My CL2/nasal pillows averages 29 LPM at 9.7 average cm/H2O.

Here is a useful graph, compliments of one our most respected Aussie members:

http://www.internetage.com/cpapinfo/leak-rates-1.html

SleepySandy · Post by **SleepySandy** » Thu Feb 01, 2007 1:13 pm

The important question is, did you have any periods of Large Leak (LL)? If so, AHI is not recorded during that time, and so would have corrupted your AHI data for that night.

My report shows Large Leak 3.5 Mins / 1% of Night.

I had no idea that Large Leaks corrupt AHI data. I don't really understand leaks in general and what it means when you have them. General common sense tells me if the mask is leaking, I'm not getting the appropriate pressure I need. But, if my AHI is really low, I don't see how it would matter (other than the Large Leaks and it not recording the AHI data).

dsm · Post by **dsm** » Thu Feb 01, 2007 4:33 pm

Leak rate is very helpful in establishing accurate HI readings by the cpap as well as informing the user (or monitoring doctor) of leaks vs airflow.

In Respironics machines, the software attempts to guess the leakrate based on consistency of airflow. Respironics decided not to use internal mask tables to hold known leak rates - it appears this was to allow any time of mask/brand to be used & they leave it up to the user of the nightly data to work out what part of the leak data is fixed & what part is accidental.

My Puritan Bennett Knightstar 330 has internal mask tables with 6 different profiles. I choose the one closest to the actual mask in use. This allows the machine to have a leak alarm that is pretty accurate (except I have disabled it - hate beeps in the night)

In Resmed machines if using a Resmed mask or one with a corresponding fixed leak profile, a leak rate table in the machine is used to subtract the fixed leak from the airflow so that their software gives a near accurate reading of real leak rate plus it allows the Resmed machines to very accurately calculate the HI numbers.

When using my respironics machines, I look at the consistency of the leak data.

DSM