Is part of vent flow obstruction ok?

[jjlady]

Is it ok to have some of the air blowing out of the mask blocked, for instance when laying on my side, I am always trying to push my pillow under the vent area so it is completey open, but sometimes I am really tired and part of it will be lightly obstructed, is that ok? Will I be suffocating myself??

[Pugsy]

Blocking the vent is not ideal because the venting purpose is to expel the carbon dioxide that is in our own exhaled breath.
If it can't vent properly there is a possibility of rebreathing some of that carbon dioxide. Might be more critical at lower pressures than at higher pressures but I am not sure. I just don't know if a "partial" blockage would hurt things all that much but it is something I wouldn't want to chance if I could help it. I know that sometimes I block my vent on my nasal pillow mask with either my arm or the bed pillow but I have a mouth that can be opened if needed. With a full face mask there isn't that option because the mouth is covered.

[archangle]

The Mirage Quattro has a leak rate of 22 L/m at a pressure of 4. Presumably, it needs 22 L/m to be "safe."

To oversimplify a bit, as you block the vent flow, the leak will drop slowly down to 0 as the blockage gets worse. At 0, you either suffocate or wake up and take the mask off. At intermediate leak rates, you're getting less O2 and more CO2 than you should. You'll have some of the same effects of having apnea.

You probably do have at least a little breathing room. There's probably some safety margin at 22, and if your pressure is higher, your leak rate will be a little higher than 22, but not as much as you might think.

If you are blocking your vent, you don't really know how much you're blocking it.

Another safety factor is the question of how badly you're blocking the vent. While I don't recommend it, having something lightly laying over the vent holes wouldn't necessarily block the air from coming out of the vent.

Luckily, you have a Respironics CPAP, not a ResMed. It records the actual leak rates. You can install the free SleepyHead program on your computer and see your leak rate on a graph. It will show how low your leak rate gets through the night, and you can see if you're blocking the vents.

Edit - Correction, SleepyHead doesn't work yet with the PRS1 mod 60 machines. Hopefully, the author will fix this sometime soon. You'd have to use the Encore Basic software.

[jjlady]

This sucks as I have to be hyper aware while on my side if any thing is blocking any part of the airflow, and I toss and turn a lot!

[greatunclebill]

don't overthink this stuff. lots of people including me sleep from side to side and probably inadvertently cover their vent holes. most people won't know it because they are sleeping. besides that, your pillow is probably porous and the exhaust flow could go into or through it. it's not like theres a total blockage of your vents.

you should get encore basic and monitor your vent/leak stats as best as you can. if you really have a 60 series machine, sleepyhead is not yet compatible with it. pm pugsy for a link to encore basic.

the vent flow rates, or intentional leak rates for quattro and quattro fx are the same: 22,32,41,48 and 54 for pressures of 4,8,12,16 and 20.

[Julie]

I don't know if people sleep through blockage or not... I've woken up a few times feeling disoriented, dizzy, strange, took off the mask, and had to wait maybe 20 mins. until I felt relatively normal again, and I'm quite sure that's what the problem was - you'd have to be here to see why I said that to believe it because of how I sleep - and normally nothing at all wakes me. Not something I want to do casually and certainly not being aware but careless about it.

[DoriC]

It seems that a "mushy" pillow is not good. My husband tried a nice soft down pillow and I heard some strange sounds and realized his head was buried into the pillow blocking the vent. I woke him before there were any problems. So we went back to his contour memory foam. I'm still looking for the perfect pillow for side sleeping with a FFM that will not spring leaks. A few people have recommended the Sobakawa pillow that's now being sold in larger sizes than the original travel size which I might try...so what's another pillow!

[LinkC]

1. Manufacturers tend to overkill on safety. The only thing they hate worse than killing customers is the resultant lawsuits.

2. If you hear air, it's escaping. If you managed to significantly block the vents, you'd almost certainly have major mask leaks elsewhere, and wake up.

3. Exhaled air is not as depleted as most people think. If it were, mouth-to-mouth would kill you, not save you.

Bottom line: I wouldn't lose sleep worrying about adequate venting.