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AitFit F20 With Dreamstation - AAV Issues

Just purchased a new AirFit F20 mask after using the F+P Simplus mask.

I find the Simplus has been leaking around the nose area into my eyes - I think its quite common, very annoying.

The new F20 fits and seals really well, really comfortable also - however the anti asphyxia valve keeps opening and shutting randomly frequently. Disturbs my sleep and the wifes - worst than snoring in her words.

I cant work out what is triggering it to close over the machine inlet. Some cases I can breathe out heavily and it doesn't close over the inlet testing it.

My  Dreamstation is set for 4cmH2O  to start - well within the specs for the F20 - and A-Flex @ 1. Mask type is off. 90% pressure is usually 6 - 8 cmH2O. I have set the machine to start @ 6cmH2o - with the Same Results.

Any ideas I really like this mask - even thought of removing the AAV but even though we haven't had a power outage for awhile - not really worth the risk I read.

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AAV is a safety feature. Never remove a safety feature.

Welcome Stick around. We have quite a few members from the land down under.

The machine pressure is supposed to close the AAV which opens the mask to atmosphere in the event of the blower stopping.

May I suggest you download Sleepyhead software. Posting some graphs may permit the machine to be fine tuned with a slightly higher EPAP to keep the AAV closed; and even improve therapy. https://sleepyhead.jedimark.net

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I have been using Sleepyhead since I started treatment as the Dreammapper app doesn't really give me enough info.

I have not seen a leak rate graph like that, and the misses indicated that it seem to coincide with the AAV noise - the Simplus mask when it leaks its massive spikes and the bridge of the nose leak doesn't seem to register as its so fine (sometimes I think its not a leak but where the vent holes are)

F20 Mask:

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A Simplus likes to be positioned lower than what you would expect.  I believe the intended leak is 24 L/min.  

You might see an additional improvement in your AHI by upping your bottom pressure from 4 to 7 and bringing down your upper limit to about 11.  This will tighten the response range that seems to help the CPAP's algorithm.
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Increasing the lower pressure might also help to keep the AAV from opening and closing so easily. I think your problem with the AAV opening and closing so much imay be due to the low pressure and subsequently low flow rate. The "massive spikes" that you see on pressure are really not all that massive. They just look that way due to the low maximum pressure on the graph. The spikes are how the PR machine checks to see if maybe you need a higher pressure. If the higher pressure does not help then it returns to the original pressure. At 4 cm/H2O pressure the AAV may not close of the vent completely and when the machine tests a higher pressure it may slap the flappers completely closed.

Just my thoughts. Increasing the lower pressure limit to 5.0 or 6.0 for one night should tell you if what I am theorizing is correct.

Best Regards,


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PaytonA passed away in September 2017
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Hi kymmitsu,
WELCOME! to the forum.!
Hang in there for more suggestions and good luck to you with your CPAP therapy and getting it fine-tuned to better meet your needs.
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If it's not working well, could it possibly be faulty? Have you asked your DME?

I'm sorry I don't know this mask well enough to comment more competently.
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Seem to go alright last night - no complaints of the AAV noise.

Ill see tonight - thanks for your help
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