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Why does the mask valve sometime 'thump'? - Printable Version

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Why does the mask valve sometime 'thump'? - StevesSp - 05-14-2022

I can't recall what the conditions were at the time, but I am occasionally aware of the little flappy valve in my Resmed FF mask shutting off with a little 'thump'. It happened several times in a row this morning, while i was awake enough to notice. I couldn't figure out why it happens but assume it's when I do something, perhaps not exhaling for a while or breathing out of synch with the machine?

Looking at my charts revealed literally nothing other than the usual sleep/wake transition junk. theer were no events during that period and no flow limitations - that I can see at least.

Why does the valve do this?


RE: Why does the mask valve sometime 'thump'? - Sleeprider - 05-14-2022

Are you certain it was not a humidifier chamber not completely seated? That's what I get sometimes.


RE: Why does the mask valve sometime 'thump'? - StevesSp - 05-14-2022

It's definitely the mask valve. I can feel it thump as well as hear it. I can force it to happen by turning the machine off but then carrying on breathing, when it thumps to and fro. I can't figure out why it happens when the machine is running though.


RE: Why does the mask valve sometime 'thump'? - BobbieM - 05-14-2022

Me too. I thought it was just me. Very definitely the mask. A clear thump. There is no pattern. Sometimes it happens several days in a row and sometimes nothing for months. I've never been awaken by a thump so I assume it has to do with a change of breathing when I wake up.


RE: Why does the mask valve sometime 'thump'? - Dog Slobber - 05-15-2022

The thumping is caused by the Anti Asphyxiation (AA) valve opening and closing. The pressure typically keeps it closed and it opens should there be a power or CPAP failure.

If it is opening/closing during therapy, you are probably take a long deep breath and drawing more air than the device is capable of providing.  Increase pressure or consciously take less deep breaths.

Turn your machine off, take some breaths, with a mirror watch the AA valve, you will see it open and close, the thumping will align with the closing of the valve.


RE: Why does the mask valve sometime 'thump'? - Sleepster - 05-15-2022

I think the noise is caused by drops of water on the valve flap or seal. This can happen if you over fill the humidifier tub, have rain out, or if you washed the mask and it didn't completely dry.


RE: Why does the mask valve sometime 'thump'? - Big Guy - 05-15-2022

Yes, I have experienced the same issue (noise). Not sure why it occurs, but it seems to do it randomly. 

It's definitely in the mask connection, not in the water reservoir or a rain-out issue.


RE: Why does the mask valve sometime 'thump'? - StevesSp - 05-15-2022

It happened again this morning, but this time I was able to figure out that the thump occurs at the end of an exhalation. I'm not sure if that's a clue to the cause.


RE: Why does the mask valve sometime 'thump'? - StevesSp - 05-15-2022

(05-15-2022, 08:55 AM)Sleepster Wrote: I think the noise is caused by drops of water on the valve flap or seal. This can happen if you over fill the humidifier tub, have rain out, or if you washed the mask and it didn't completely dry.

That's possible. It isn't the water itself making the noise, but perhaps droplets can interfere with the normal operation of the valve.


RE: Why does the mask valve sometime 'thump'? - Homerec130 - 05-15-2022

I get the same thing, usually when I first put the mask on while the system is ramping up. I have a short ramp period, more out of habit than anything else. Beside hearing the thump, I can also feel it. Seeing as it goes away in several breaths, I don't really worry about it.