help with leak rates

I was wondering if there is a standard number for the highest leak rate you want to keep cpap theraputic. I have a pressure of 7 and range from 29.5-32.0 on my l/min rate. It appears in my manual for the mirage ultra ffm that the flow curve is about 27 or so (it says 32 for pressure of 8 ) Just wondering if leaks are causing me to still be tired. Thanks,
Jen

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Leaks are good and bad. A good leak is called the vent flow rate or flush rate, airflow through the vents, purposely designed to flush away exhaled carbon dioxide. Leakage above that rate is a bad leak from a poorly selected, sized, or fitted mask, leaking because it doesn’t rest securely on your face or nostrils. The higher the pressure, the higher the vent flow rate and bad leak rate. Wash your face to remove facial oils before using a mask, and avoid skin moisturizer on your face at night. The mask shouldn’t leak into your eyes (causing conjunctivitis) or anywhere else around its seal. For subtle leaks with nasal pillows, you may not be able to detect leaks by how they feel on your face. Use your hand to feel around the mask for leaks. Another way to detect leaks is by sound. If your mask turns into a sonar device, echoing a new sound off of bed pillows, you have a leak. If your full face mask makes a rude raspberry noise or turns into a wind instrument, you have a large leak.

For a discussion thread on interpreting leak rates, see viewtopic/t14536/Meaning-of-System-Leak-Numbers.html

For a table of vent flow rates of various masks compiled by cpaptalker dsm from other users quoting the manufacturers’ published vent flow rates,
see http://www.internetage.com/cpapinfo/leak-rates-1.html .
The numbers along the top line of the chart are machine pressure in cm/H2O. This table is useful if you want to compare the necessary vent flow rate with the leak rate shown by your machine software. The difference allows you to assess how badly your mask is leaking due to a poor fit.

Happy reading!
D.

Thanks for the reply. I am still a little confused about some of the numbers. The graph that shows all the masks and leak rates does not go down to a pressure of 7. Also, my machine gives me l/min and alot of the post seem to talk a about l/sec so trying to figure up if I am still leaking much or not...for instance last nights readings- leak-31.6 l/min, AHI-6.4...I am guessing from my ultra mirage user guide to have a vent flow of about 27 l/min so still trying to figure if it is leaking much or not. I do not feel any leaks at night. Thanks

look at the leak graph on the software report - not the LED information

now if you don't have the software, get it - it is the only way to know if leaks are really bad

reefdreamer,

I don't think there is a definitive answer to your question about a standard leak rate. The software I use has a big ole red line when the total leak rate is 24 l/min above the designed leak rate, but I don't know the reasoning behind it. The goal is to minimize the leak number.

The reason people talk abut l/min and l/sec is that the one manufacturer (respironics) reports their data in l/min, while another (resmed) reports their data in l/sec. I'm not sure what the other manufacturers report their leak rates as. For a pressure of 7, your mask with a perfect seal, should leak at 30 l/min. Your reported leak rate is 31.6, so you're pretty darned close.

Jules is correct about the software. The "quality" of leak can only be determined by looking at the software. In other words, do you have a slow, small leak or a short major leak? In my opinion (and you know what they say about opinions), a slow small leak is not that big of a deal (other than the possibility of air drying out the eyes). A short, large leak can interfere with your treatment if you have apneas etc during the leak events.

Good Luck,