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Inhaling exhaled CO2 gases
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bryank1 Offline

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Post: #1
Inhaling exhaled CO2 gases
Does anyone know if there is any CPAP industry wide standard that is used for masks and mask types as far as how much CO2 is re-inhaled in any particular mask?

I have tried quite a few masks. The Quatro FX has the tiny holes for constant release. I am assuming after air is exhaled it is mixed with the constant flow of air that is pushed out those holes. I would think there must be a small amount of C02 that is re-inhaled. I noticed on some masks that the constant air stream is almost nonexistent. For instance on a nasal pillow mask, how is exhaled air released without re-breathing it back in?
11-16-2012 11:06 PM
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PaulaO2 Offline
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Post: #2
RE: Inhaling exhaled CO2 gases
All masks have an exhaust port. Some have one hole, other have several. My Breeze (pillow mask) has one big hole in the frame that holds the pillows. I had one nasal pillow mask that had a whole bunch and while it was quieter, it was a PITA to keep from hitting the pillow or sheet and causing more noise.

I would assume that nearly all CO2 is vented due to the constant flowing air. Unless you are panting, it's getting recycled fairly quickly. Unless you are putting out more air than it is putting in, the risk of re-breathing is minimal.

I'm still looking for the information. The key is to put in the right search term. arrrgh

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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
11-16-2012 11:21 PM
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PaulaO2 Offline
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Post: #3
RE: Inhaling exhaled CO2 gases
Here's an interesting study. .PDF format. The main website is in Spanish so not sure what the site is. It is testing a prototype mask against two others but it doesn't say what the prototype was. My eyes are a little too tired to figure what they are saying.

http://www.archbronconeumol.org/watermar...org&lan=en

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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
11-16-2012 11:32 PM
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zonk Offline

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Post: #4
RE: Inhaling exhaled CO2 gases
Full face masks have an anti-asphyxia valve ... a safety feature which allows you to breath thru ... in event of power failure

Its important to check the valve is not damaged and working properly

All masks designed with vents that meets some legal requirement standard for protection against re-breathing

As with all masks comes with a warning ... some re-breathing may occur at low pressures

The vent flow rate vary from mask to mask ... the higher pressure ... the higher mask vents leak (intentional leak)
Its important to kept clear of bed covers

Your Quattro FX vents leak 34 L/min at pressure 12 but the S9 take this into account and report unintentional leak (mask leak)
Other machines report total leak = intentional leak plus unintentional leak). You only have to set mask type
11-17-2012 01:05 AM
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JJJ Offline

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Post: #5
RE: Inhaling exhaled CO2 gases
(11-16-2012 11:32 PM)PaulaO2 Wrote:  Here's an interesting study. .PDF format. The main website is in Spanish so not sure what the site is. It is testing a prototype mask against two others but it doesn't say what the prototype was. My eyes are a little too tired to figure what they are saying.
http://www.archbronconeumol.org/watermar...org&lan=en

Cruburos Metálicos is a large company in Spain. They claim 1,000 employees and 200 distributors, although none of them seem to be outside of Europe. Their main product line seems to be industrial gases. I couldn't figure out much about the mask in question, except that it is probably not sold outside of Europe.
11-17-2012 01:16 AM
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bryank1 Offline

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Post: #6
RE: Inhaling exhaled CO2 gases
(11-16-2012 11:32 PM)PaulaO2 Wrote:  Here's an interesting study. .PDF format. The main website is in Spanish so not sure what the site is. It is testing a prototype mask against two others but it doesn't say what the prototype was. My eyes are a little too tired to figure what they are saying.

http://www.archbronconeumol.org/watermar...org&lan=en

That is an interesting study, seems that each mask had a different rating on co2, which is what I noticed after using several masks. Most of the full face masks seem to have the largest openings for constant air flow out of the mask. Then nasals seem to have a small amount of air and the pillow types very small amount of air. Just wondering how sufficient that little amount of air exhausted by the pillow or nasal mask is since it is significantly less than a full face.
11-22-2012 07:31 PM
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PaulaO2 Offline
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Post: #7
RE: Inhaling exhaled CO2 gases
I think it is acceptable because the air exchange is smaller. If I am thinking correctly, the full face mask has a larger space for the exhale breath to sit in. A larger air exchange is needed because there's more air to move. Like, you need a big fan for a big room and a smaller fan for a smaller room in order to properly move the air around.

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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
11-22-2012 09:14 PM
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bryank1 Offline

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Post: #8
RE: Inhaling exhaled CO2 gases
(11-22-2012 09:14 PM)PaulaO2 Wrote:  I think it is acceptable because the air exchange is smaller. If I am thinking correctly, the full face mask has a larger space for the exhale breath to sit in. A larger air exchange is needed because there's more air to move. Like, you need a big fan for a big room and a smaller fan for a smaller room in order to properly move the air around.

Good analogy, I'm sure that maybe how the masks are designed around that criteria. I'm still seeing it a different way.

If you can clone an individual side by side and put a pillow mask on one and a full face on another, the constant is the amount of air that each lung would exhale on each. One mask might be bigger, but the smaller nasal pillow mask has to have a way to exhale the same amount of air and after trying all 3 types I'm not seeing that type of mask releasing the exhaled air.

So, for example if you cup your hand and exhale normally. The full face mixes the exhaled air with the constant pressure air out the holes and there more than likely is enough airflow to get all the air out before you inhale back in. On the nasal pillow type(or even a nasal mask-at least the ones I have used), those holes don't seem to let out enough of the exhaled breath stroke. However, the exhaled air is obviously going somewhere. I am just not seeing the amount that is exhaled out going out those holes. So where is the air going?
11-22-2012 10:23 PM
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archangle Offline
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Post: #9
RE: Inhaling exhaled CO2 gases
You don't have to worry about rebreathing CO2 as long as you're using standard CPAP equipment in proper working order.

First, realize that you exhale Carbon Dioxide, CO2, not Carbon Monoxide, CO. Carbon MONoxide is the stuff that kills you if you have a car exhaust leak. A fair number of people confuse the two. There is no Carbon Monoxide involved in CPAP. (Except whatever pollution is in the air you breathe even without CPAP.)

Long before CPAP was thought of, we figured out the hazards of rebreathing CO2 from using ventilators. The physics of the situation are very well understood, safe levels were established, and CPAP equipment was designed to have a large safety margin.

The minimum pressure most machines will produce is 4 cmH2O. The exhaust holes are designed such that they leak out enough air at that pressure that they will clear out the exhaled air enough to prevent the build up of CO2 and depletion of O2 to harmful levels. Unless the exhaust air holes are plugged, or the machine is producing less than 4 cmH2O, you won't get enough rebreathing to be harmful.

By the way, the hazard to rebreathing air is not so much from high CO2, as it is from low O2.

Also, the effect of rebreathing some of your exhaled air is much the same as having apnea. In either case, O2 has a hard time getting into your lungs and CO2 has a hard time getting out.

Enough for one post. Time to stop to let my keyboard breathe for a bit.

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11-22-2012 10:31 PM
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PaulaO2 Offline
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Post: #10
RE: Inhaling exhaled CO2 gases
LOL Good answer!

You said it much more clearly-er than I could.

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Breathe deeply and count to zen.

INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
11-22-2012 10:54 PM
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