Acceptable Leak Rate?

[deadhead]

Hello.

Last night I used CPAP for the first time. I am using a Swift LT nasal pillow mask and a Remstar Auto M machine. I'm using it in CPAP mode for now with a pressure of 7 and C-Flex of 3. After a few hours of use last night, the system leak rate was 25.5 l/min. Is this ok? What is the acceptable range? I see a chart in the user manual showing Vent Flow Rate vs. Mask Pressure but I'm not completely sure if this is the info I'm after. If it is, then is Vent Flow Rate the same as the system leak rate (25.5) shown on the CPAP machine and is Mask Pressure the same as the pressure I set (7) on the CPAP machine?

Thanks!

[Guest]

I see a chart in the user manual showing Vent Flow Rate vs. Mask Pressure but I'm not completely sure if this is the info I'm after. If it is, then is Vent Flow Rate the same as the system leak rate (25.5) shown on the CPAP machine and is Mask Pressure the same as the pressure I set (7) on the CPAP machine?

Thanks!

It is. The rate varies with pressure and each mask is different. Keep in mind none have been calibrated to "Your machine".

[deadhead]

Hi. I'm not sure what you mean by "none have been calibrated to "Your machine"". Thanks for your help...

[Songbird]

Last night I used CPAP for the first time. I am using a Swift LT nasal pillow mask and a Remstar Auto M machine. I'm using it in CPAP mode for now with a pressure of 7 and C-Flex of 3. After a few hours of use last night, the system leak rate was 25.5 l/min. Is this ok? What is the acceptable range? I see a chart in the user manual showing Vent Flow Rate vs. Mask Pressure but I'm not completely sure if this is the info I'm after. If it is, then is Vent Flow Rate the same as the system leak rate (25.5) shown on the CPAP machine and is Mask Pressure the same as the pressure I set (7) on the CPAP machine?

Hi, Deadhead.

Yes, that's a great leak rate! I’m pretty sure the chart you’re talking about is the one I checked. It’s on page 8 of the Swift LT User Guide (http://www.resmed.com/en-us/products/se ... er-mul.pdf) in the section entitled "Pressure-Flow Curve." The chart itself has "Vent Flow Rate" along the vertical line on the left, and that’s why I think we’re talking about the same thing.

Yes, the Vent Flow Rate IS the same as the system leak rate shown on your cpap machine. It's the actual amount of air escaping from your mask. A certain amount is necessary in order to flush the C02 that we exhale, and different styles of masks have different acceptable leak rates. As the set pressure changes, a mask's acceptable leak rate will change; thus the chart in your User Guide. There's more about leaks, as well as other very helpful information, in a wonderful article written by our own Mile High Sleeper (reading the whole thing is highly recommended). Here's the link: http://smart-sleep-apnea.blogspot.com/2 ... blems.html

Yes, the Mask Pressure is the level of air pressure that’s been set for your machine. In your case, the Swift LT chart doesn’t exactly state the acceptable leak rate for a set pressure of 7 cm/H2O. But since it says the acceptable rate at 4 cm H2O is 21 and that the acceptable rate at 8 cm H2O is 28, doing the math tells me that the acceptable rate at your pressure of 7 cm H2O would be 26.25. (BTW, numbers are NOT my friends; if I figured this wrong, would someone pleeeeeease correct me?) If your AHI is too high (5.0 is acceptable; 0.0 is perfect, although elusive), one of the first things to look at is your leak rate. If it’s significantly higher than your acceptable leak rate, it either means your mask isn't sealing well somewhere and you need to fix that or, if it's anything except a full face mask, you might be sleeping with your mouth open (therefore the air isn't getting where it needs to) and you either need to find a way to keep your mouth shut (a lifelong challenge for me, btw ) or switch to a full face mask. Since your leak rate of 25.5 is below 26.25, don't worry about being a mouth breather, don't change the adjustments on your mask and be happy!

Just to repeat myself, math and science are weak areas for me. If I’ve misstated anything, I’d very much appreciate it if someone would correct what I’ve said. Thanks!!

Marsha

[deadhead]

You may not be great at science and math as you say, but you're great at being helpful. Thanks.

[Hawthorne]

Songbird - I'm not that great at math or science either but I think you explained it every well!

Deadhead, I think you can take Songbird's explanation "to the bank"! I don't know if "take it to the bank" is a US expression or not but, in Canada, it means she is right on! You have a great leak rate!

I just thought, given the economic climate, that may not be the best expression to use right now!

Doesn't matter. As Songbird said, you have a great leak rate.

[deadhead]

I don't know how my wife will feel about women telling me I have a great leak rate!

[echo]

But since it says the acceptable rate at 4 cm H2O is 21 and that the acceptable rate at 8 cm H2O is 28, doing the math tells me that the acceptable rate at your pressure of 7 cm H2O would be 26.25. (BTW, numbers are NOT my friends; if I figured this wrong, would someone pleeeeeease correct me?)

Assuming the trend is linear (that is, leak rate increases proportionally to the pressure) , then 26.25 is spot on

Hi. I'm not sure what you mean by "none have been calibrated to "Your machine"". Thanks for your help...

As for this comment, I'm not the one who made it, but I can only guess they mean the following:
On some machines, you can enter in the type of mask you're using, and the machine will automatically calculate the excess leak rate, that is [actual measured leak rate - expected leak rate for that mask at the measured pressured (the intentional leak rate) ] = [leak rate] --> And if this last number is greater than 0, that means you have leaks for other reasons besides the mask's intentional leak rate. Whew, did anyone follow that? sorry if I didn't make that clear enough.

Anyway, some machines don't do this at all, so the leak rate that you see is the total leak rate, including any unwanted leaks PLUS the intentional leak rate.

I don't know what you get if you have a machine which lets you program in the mask, but you haven't actually programmed one in - then does it use some default value for the intentional leak rate, or does it just use 0, dunno!

Ha ha, guess that was less than helpful.

[Songbird]

I don't know how my wife will feel about women telling me I have a great leak rate!

ROTFLMAO!!! Y'know, it doesn't do a lot for my "seriously hard-working State worker" image to land on the floor because I was laughing so hard. Thanks, Deadhead!!

(And thanks, everybody else, also. )

Marsha

[boston]

I just switched to a swift lt, was using a comfort gel and my leak rate was between 45-60, since switching it came down to 31.7. according to the chart im a little low, so i will wait another week or so and see what my 7 day average is then. but either way, at least for me the leak rate went down.