What exactly does leak rate mean?

[HollyDolly]

I started treatment 5 days ago. I just dowloaded the res scan software and the graph shows my leak rate for the first 2 days at 40, day 3 at 24, and day 4 and 5 at 0. Just trying to figure out what this all means. Thanks!

[DreamOn]

Welcome to the forum, HollyDolly!

I will discuss "Leak Rate" as it is reported by the ResMed machines. The other manufacturers report that differently. Leak Rate is the difference between inspiratory and expiratory airflows. Theoretically, these numbers should be equal, in which case the Leak Rate would be reported as zero. Each mask has an "expected vent flow rate," which is the amount of air it releases via the mask vent while the machine is in use. There is a setting on the ResMed machines for the mask type. The mask's "expected vent flow rate" is subtracted before the Leak Rate is reported. A Leak Rate of 24 L/min (0.4 L/sec) or less is considered "acceptable" on the ResMed machines. Anything over that, and your therapy may be adversely affected since the machine cannot compensate for the excessive loss of therapy air. Also, your other results numbers (such as AHI) may be inaccurate if the Leak Rate is excessive.

With a ResMed machine, it's good to get the Leak Rate as close to zero as possible. Leaks can come from a displaced mask seal or nasal pillows that leak air during the night, or you can be losing therapy air from mouth leaks if you're using a nasal or nasal pillows mask. When we are deep asleep, all our muscles relax, which can cause our mouth to fall open. Some people use a chin strap or tape their mouths to prevent that loss of therapy air. Others have to wear a full-face mask. Leaks can also come from holes in hoses or connections, although it's usually coming from mask/nasal pillows or mouth.

So, your Leak Rate the first two days was too high (at 40), Day 3 was right on the border (at 24), and Days 4 and 5 were perfect (at 0)!

By the way, I see that you're using the SoftGel nasal mask. Just thought I'd mention that that mask frame also fits the Activa LT cushion, in case you want to try that one sometime in the future.

[dsm]

I started treatment 5 days ago. I just dowloaded the res scan software and the graph shows my leak rate for the first 2 days at 40, day 3 at 24, and day 4 and 5 at 0. Just trying to figure out what this all means. Thanks!

Another explanation,

Leak rate is the amount of air leaking or escaping from your mask or your mouth during the night.

But, there are different aspects to this leaking.

1) Almost all masks have a 'Fixed leak' rate. This is represented by the small holes in your mask that let air out all the time. The purpose of the 'fixed leak' is to help flush CO2 from your mask and airhose to minimize rebreathing of your exhaled air

2) 'Accidental leak' rate. This is the measure of accidental leaking of air.

2-a) Mask accidental leaks - this is where the accidental leaks is caused by air escaping from around the mask seal.
2-b) Mouth accidental leaks - this is where the user has a nasal mask & during the night opens their mouth and air escapes


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For Resmed machines, when you set the mask type in the menu, the machine automatically subtracts the known fixed leak rate and thus normally will only report the accidental leak that is occurring. Under normal conditions (no accidental leaking) the leak data should show as 0 leak.

For most Respironics machines, the data includes the fixed leak rate as well as the accidental. In order to know what the accidental leak rate is at any point in the data, one has to know the fixed leak rate data for the mask in use, the pressure at the time of the leak, then subtract the fixed leak value from the reported leak, and this should give you the accidental leak rate.

Hope this helps provide some extra insights.

DSM

[HollyDolly]

Thanks for the replies!

[Velbor]

wiki/index.php/Mask_Leaks