Reducing rebreathing

[littorine]

Newbie here, looking for recommendations for types of masks and/or tubing to minimize rebreathing as much as possible. I know all masks have sufficient venting to be safe, but I'm very sensitive to elevated CO2 levels (can't go in malls, airplanes, or many office buildings because the CO2 is too high for me; and it takes hours for the cognitive effects to wear off if the CO2 is too high), so even mild, generally safe levels of rebreathing are problematic for me. I'm currently using a ResMed Mirage FX mask with pinhole vents and a Respironics REMstar Auto A-Flex System One machine, but I've seen that some masks and tubes are advertised with valves to reduce rebreathing. I'd appreciate any recommendations for equipment that minimizes rebreathing. Thanks!

[raisedfist]

Any mask with a smaller surface area, such as a nasal pillows mask, has less dead space - therefore less chance of re breathing. If you're a mouth breather you can always wear a nasal mask and tape your mouth shut. Many people here do just that.

If you're using the APAP mode, increasing the min pressure will also increase the amount of expired air being vented. Each mask has the vent rates in relation to the pressure set in the manual.

[Wulfman...]

Read and then fill out your profile.......including all your settings.

viewtopic/t172378/Sticky--Newbies-PLEAS ... STING.html


Den

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[Janknitz]

I think you can look at the specs of any mask and see what the vent rate is. That might help in your decision.

[ragtopcircus]

I've seen that some masks and tubes are advertised with valves to reduce rebreathing. I'd appreciate any recommendations for equipment that minimizes rebreathing. Thanks!

If you are referring to anti-asphyxiation valves, they are not intended to reduce rebreathing. The valve remains closed in normal operation. It opens if the machine shuts off so you can get enough air. They are typically found only on full face masks, because if the machine shuts off (for example, in a power failure) when you are are wearing a pillow mask, you can just open your mouth.

Some people have the opposite problem: low CO2 levels can cause Central Apnea, because CO2 is a breathing trigger. This can be induced if the difference between inhalation and exhalation pressure is too high. Unfortunately, the options are limited with your machine, but it might be worthwhile to at least set the Flex to 3 if you have not already.

Do you use supplemental oxygen?

[chunkyfrog]

. . .
I'm very sensitive to elevated CO2 levels

Has this sensitivity been medically confirmed?
If so, then you should be referred to an appropriate specialist for treatment.
The source could be physical or psychological, but not treatable online.

[Miss Emerita]

. . .
I'm very sensitive to elevated CO2 levels

Has this sensitivity been medically confirmed?
If so, then you should be referred to an appropriate specialist for treatment.
The source could be physical or psychological, but not treatable online.

+1

[littorine]

Has this sensitivity been medically confirmed?
If so, then you should be referred to an appropriate specialist for treatment.
The source could be physical or psychological, but not treatable online.

Yes, it has been confirmed medically, and the treatment is to avoid high CO2 environments. I'm not looking online for treatment, just advice about CPAP masks. Thanks.

[littorine]

If you are referring to anti-asphyxiation valves, they are not intended to reduce rebreathing. The valve remains closed in normal operation. It opens if the machine shuts off so you can get enough air.

Thanks, that's very helpful information.

Unfortunately, the options are limited with your machine, but it might be worthwhile to at least set the Flex to 3 if you have not already.
Do you use supplemental oxygen?

Thanks, I'll try that! No supplemental oxygen, since I don't have any problems in that regard.

[palerider]

Has this sensitivity been medically confirmed?
If so, then you should be referred to an appropriate specialist for treatment.
The source could be physical or psychological, but not treatable online.

Yes, it has been confirmed medically, and the treatment is to avoid high CO2 environments. I'm not looking online for treatment, just advice about CPAP masks. Thanks.

I've never encountered a CPAP mask that has any significant amount of CO2 rebreathing.

It's very easy to tell, as I'm breathing, I can feel the vent air change temperature as it's purging my exhaled breath and goes cool again before the next inhalation.

[littorine]

I've never encountered a CPAP mask that has any significant amount of CO2 rebreathing.

It's very easy to tell, as I'm breathing, I can feel the vent air change temperature as it's purging my exhaled breath and goes cool again before the next inhalation.

That doesn't mean all the CO2 is gone, but that isn't a problem for most people since they can tolerate some CO2 rebreathing. I've checked the CO2 outside the vents of my mask using a CO2 monitor and can confirm that it's well higher than ambient air (about 1400 ppm in a room that's kept below 550 ppm, compared to about 1900 ppm when holding the monitor at the same distance without the mask), but the monitor also shows higher CO2 inside the mask just prior to inspiration. It's impossible to get a good reading inside the mask because of having to stick the monitor underneath it, which causes a big air leak and diffusion of the air inside the mask and therefore artificially low levels, but I've had readings from 750-1500 ppm. Again, this is NOT an issue for the average person - I've been in hotel rooms with CO2 levels of 1500 ppm, and no one thinks twice about sleeping in them, except those of us who carry around CO2 monitors!

[palerider]

I've never encountered a CPAP mask that has any significant amount of CO2 rebreathing.

It's very easy to tell, as I'm breathing, I can feel the vent air change temperature as it's purging my exhaled breath and goes cool again before the next inhalation.

That doesn't mean all the CO2 is gone, but that isn't a problem for most people since they can tolerate some CO2 rebreathing. I've checked the CO2 outside the vents of my mask using a CO2 monitor and can confirm that it's well higher than ambient air (about 1400 ppm in a room that's kept below 550 ppm, compared to about 1900 ppm when holding the monitor at the same distance without the mask), At what point in the respiration cycle? the co2 concentration varies wildly.

[littorine]

At what point in the respiration cycle? the co2 concentration varies wildly.

The inside mask readings? I stick the meter in just before I would naturally breathe in (but holding my breath). My CO2 monitor is designed to reflect ambient CO2, and doesn't respond quickly enough to record the ups and downs of a respiratory cycle, so the measurements outside the vents and at an equivalent distance from my mouth reflect the maximum it's exposed to, rather than any particular instant.

[littorine]

It might be worthwhile to at least set the Flex to 3 if you have not already.

Thank you! I tried that last night and felt much clearer and energetic this morning.

[zonker]

It might be worthwhile to at least set the Flex to 3 if you have not already.

Thank you! I tried that last night and felt much clearer and energetic this morning.

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