Mask Depenent Pressure Differences

Jim Eads · Post by **Jim Eads** » Tue Mar 07, 2006 1:59 pm

I usually use an Aura and my APAP pressure runs around 11.

I recently purchased an H&P Flexifit full face mask due to a headcold. I'm finding the pressure using this mask is in the neighgorhood of 16.

Why would a full face mask required higher pressure?

Jim

neverbetter · Post by **neverbetter** » Tue Mar 07, 2006 4:18 pm

Simple.....LEAKS !

Linda3032 · Post by **Linda3032** » Tue Mar 07, 2006 11:46 pm

Jim, that is interesting. What does your software say? A lotta leaks?

With my Nasalaire, I had a 90% pressure of 7 (and sometimes 6). But with the Aura, I'm running a steady 8. I have much fewer leaks with the Aura. Plus I have a lower AHI and SI.

And the really good thing is, I NEVER feel the pressure with the Aura. I have to feel the exhaust to see if it's even on. With the Nasalaire, I would wake up at night and have to hit the ramp button because I could sure tell if I was hitting 8 or 9.

Snoredog · Post by **Snoredog** » Wed Mar 08, 2006 2:12 am

when you use an interface with smaller delivery tubes it can impact the ability of the autopap to "read" your events accurately. This is not so much of a problem using a straight cpap machine since it doesn't need to read any of your events. But on an autopap it must sample your breathing pattern store it in memory, if the delivery tubes are smaller than what the machine is expecting to see it can throw off its ability to respond to SDB events, it doesn't change the pressure so much as it changes the volume of air as you breathe in and out. Smaller delivery tubes seem to skew that measurement on the autopaps.

Most machine mfgs say they only recommend use of their own interfaces for that reason, if you look at a Resmed machine they will even have a menu mask selection in the machine setup field to compensate for the type of mask interface being used.

Also most masks have to have a built-in leak rate so to speak for CO2 washout, most fall into the range of 12-16LPM, if your mask interface has more than that then the machine will think its a large leak and try to compensate for it with increased pressure.

Jim Eads · Post by **Jim Eads** » Wed Mar 08, 2006 9:57 am

I am definitely getting more leaks with the FlexiFit.

I finally got it adjusted properly last nigh but had it really tight. The machine ran a 90% of 15.7 versus about 11 for the Aura. Also, it's showing an AHI of about 15 versus about 2 with the Aura.

I can also tell from the way I feel that I'm not sleeping as good with the FlexiFit.

I guess if you have to wear a full face mask, it's not all that bad but compared to the Aura... well there is no comparison.

I wondering if the configuration of the throat is different with the mouth open than it is with the mouth closed that would cause apneas to occur easier with the mouth closed?

Jim

Darth Vader Look · Post by **Darth Vader Look** » Thu Mar 09, 2006 1:11 am

Jim, my last trial mask was the 431 flexi-fit and I used the large cushion. I thought the under the chin was a good concept but the mask leaked around the bridge of the nose and had to be strapped down tight. This made it uncomfortable for me so I returned it for the Resmed Activa which works great. I have had the Ultra Mirage full face and liked that one as well. It will likely be my next mask and I will purchase it here a cpap.com.

NightHawkeye · Post by **NightHawkeye** » Thu Mar 09, 2006 6:00 am

Jim Eads wrote:I wondering if the configuration of the throat is different with the mouth open than it is with the mouth closed that would cause apneas to occur easier with the mouth closed?

Bingo! I had the same problem with my Ultra Mirage Full Face Mask. It was my first mask and I couldn't understand why when I got leaks under control that my AHI went up. (I kept pressure constant, rather than allowing pressure to go up as you have.) After a couple of weeks it finally dawned on me that by tightening the mask down so much I'd actually pushed my lower jaw back and induced a greater number of apneas! When I posted about my discovery on this forum, a number of folks responded that they also had apnea which was related to jaw position.

Sounds like that's probably what's happening in your case too, Jim. I have a theory, which I haven't tested yet, that using a chin strap might hold the jaw in position well enough to allow using my full face mask. Just got the chin strap yesterday, but am liking my Swift nasal pillows mask so well now that I didn't want to experiment with the chin strap last night. .

Regards,
Bill