Everest Aura & CO2 clearance

[gracie97]

Is anybody else here concerned about how well the Aura clears CO2?

I recall complaining about the noise and wind from the CO2 port on a previous interface to my sleep specialist, asking why the port couldn’t be away from the face. His response was that the further the port is from the nose, the less easily CO2 could clear from it and the more likely CO2 build up would be.

The Aura port is quite a bit further from the nose than any other interface I’ve seen yet. The CO2 has to travel way up those two narrow tubes against the pressure of the incoming air to escape.

What assurance do we have that the Aura clears CO2 adequately or as well as, say, the Swift? Is there some way we can compare CO2 clearance for different interfaces?

I began wondering about this after seeing posts here from people who described feeling a bit starved for air using the Aura: Could it be that they are getting plenty of air but that the air they are getting has too much CO2, leading to a slight sense of suffocation?

Any thoughts or information on this topic appreciated.

Gracie

(PS: I'm currently using the Aura, though. But I do get a bit of sense of air shortage with it, even though it fit me out of the box with no bending of the wires needed. And have also been having more headaches since starting with Aura a week ago.)

[Jere]

When I switched from the Swift to the Aura I experienced a definite drop in pressure. I increased my pressure by 1 to compensate and it has been smooth sailing ever since.

I had CO2 issues with the Swift when ever a pillow or blanket got too close to the vent holes. I don't have this problem with the Aura.

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CPAPopedia Keywords Contained In This Post (Click For Definition): swift, Aura

[ozij]

His response was that the further the port is from the nose, the less easily CO2 could clear from it and the more likely CO2 build up would be.

Sorry, that doesn't make sense to me. That's the docotor rationalizing, not analysing. You've got air blowing into the mask, and being blown out of it constantly. This is not a one time gust that grows weaker as you get further from the source. This is new air constantly pushing away whatever is in front of it. Why in the world should the CO2 accumulate? The CO2 you exhale get carried away by that stream.

What assurance do we have that the Aura clears CO2 adequately or as well as, say, the Swift?

The fact that the interface was OKayed by the FDA?

(PS: I'm currently using the Aura, though. But I do get a bit of sense of air shortage with it, even though it fit me out of the box with no bending of the wires needed. And have also been having more headaches since starting with Aura a week ago.)

* I notice you're using the Aura on a Remstar Pro 2. Do you have software to report your results? Have you checked them?

* Have you checked for leaks around the nostrils? They're there even when you can't hear them - you have to put the back of you hand to the area around the nostrils to make sure you don't have any leaks - you might be undertreated since the pressure is escaping. The rubber bands are a tremendous help with that for me.

* I had headaches on my first nights of Aura use because of the way I put on the headgear - it put pressure on the muscles just below my occiput, and that's where tension headaches start. I also took me a while to find a way to snuggle into the pillow without dislodging the heagear - another reason for developing tension in my neck muscles.

O.

[Guest]

Sorry ozij,

I dissagree with you. The further away the port is from the nose, the more CO2 you will rebreath. If the pressure is not sufficient to wash the CO2 away fast enough, there is no question that you will be rebreathing it.

If this were not the case, mask/xPAP manufacturers would put the port on the hose where it connects to the machine (or on the machine itself)--the masks would then be whisper quiet. Unfortunately, we would all suffocate.


-John

[deltadave]

The best way to measure CO2 levels would be to use a CO2 monitor



But even many sleep labs don't have them.

Hey o., wouldn't this be a great segue for the Complex Sleep Disordered Breathing thread?

You might be able to hazard a guess if you can figure out the volume of the interface in ml. Fill it up with water (yeah, close the nasal openings) to the point of the exhalation port.

You usually need about 100-150 ml before you even start to influence your body's CO2 levels.

Even then you will usually just breathe a little deeper to take care of the difference.

Now, occluding ports is a whole 'nother matter....
deltadave

[ozij]

If the pressure is not sufficient to wash the CO2 away fast enough, there is no question that you will be rebreathing it.

(my added emphasis)

Operative word: If. "There in no question" etc. , if the hypothesis of the pressure being too low is accepted.
I have every reason to believe the pressure on an FDA okayed device is sufficient.

And before we all get into an argument about what we should and shouldn't believe, I'ld like to make it clear that the most important datum is how we feel, and I take Gracie's headaches seriously - something in her combo is not giving her the treatment she needs - which is why I pointed out things she can control, and should check.

Gracie's options:
* Stop using a comfortable interface because of a hypothetical possibility that it is not clearing CO2 properly.

* Make sure there are no leaks

* Raise the pressure 1 cm/H2O

The second and third options do not exclude one another.

Hey o., wouldn't this be a great segue for the Complex Sleep Disordered Breathing thread?

Sure would! Between worrying about too much CO2 clearance, and too little CO2 clearance, we can all drive ourselves sleepless...

I had the nasal seal (medium) soaking in a vinegar solution now, so I measured how much water it contained: maybe 25 ml. I estimate the addtional volume to the ports at about 10 ml.

Let us know what you decide to do and how you feel Gracie! I'm pretty sure rested gal will buy the aura from you if you decide to give up on it and if it has a transparent "headgear holder". Unless she's already found one....

O.

P.S. - Gracie, do your best to get the card reader and software - it'll make it much easier for you to follow the ups and downs of your treatment.

[deltadave]

wouldn't this be a great segue for the Complex Sleep Disordered Breathing thread?

Well then, this might provide for some entertaining reading...

Complex Sleep Related Breathing Disorder

deltadave

[WillSucceed]

I purchased an Aura and found that I had concerns about how far the CO2 vent was from my nose. I was worried about CO2 washout and, I suspected that the distance of the vent from the nose contributed to accumulation of rain.

I ended up selling my Aura to another user and have not heard how she is making out. For me, the Aura was a bust; I'm well aware that others love it. As with all masks, one users' poison is another users' pleasure.

[john5757]

I purchased an Aura and found that I had concerns about how far the CO2 vent was from my nose. I was worried about CO2 washout and, I suspected that the distance of the vent from the nose contributed to accumulation of rain.
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WillSucceed you brought up a interesting point. I was going to try the Aura mostly for the vent going straight and maybe some more comfort for the nasal pillows. The swift gives me the best treatment and the DreamFit as the most comfort. The DreamFit gives good number reading on the machine but since the vent rate is low I feel that there is more C02 re breathing and after a period of time after a month or so I was getting to be a little bit more tired with the DreamFit as compared to the Swift which does have a higher vent leak rate. With the Aura the exhale has to fight against the direction of the incoming pressure in order for the exhaust to escape. Some full size mask like the ResMed Ultra Mirage have the vent far away near the top but the exhaust does not have to fight against the incoming pressure to escape but just drift to the top with incoming air at the bottom and the exhaust at the top. While not perfect, like air going straight out, the Swift gives me good treatment and I will still use the Dreamfit since it is very comfortable for my needs. There is a whole topic of CO2 rebreathing under the disorder breathing on another board and please do not get me started on that issue.

[Snoozie]

Interesting post. I have been rotating between the Aura and Swift for some time now. I always have breathing problems with the Aura and don't feel as well when using it, but love the comfort and just keep trying and hoping it will get better. The puzzling part is that my AHI's are close on both even though I feel markedly worse when using the Aura. Bottom line - do AHI's tell you how much CO you are breathing in? Not to my knowledge. Is it possible that AHI's would be the same whether or not you are getting an increase in CO because you are still getting the correct amount of pressure? Also, does anyone know how these devices are tested before being marketed? Not saying anything bad about any device, but why are AHI's better with some and not with others? Just curiously thinking out loud. Also, what are the long term effects of heavy chest breathing? Can an increase of forced breathing over a long term cause any kind of strain on your heart? My chest sometimes hurts after wearing the Aura, which is a great concern to me. I think it is a perfect design, just needs some more professional tweaking.

[Jerry69]

I've been mulling over this topic and the responses.

Now, I'm thinking out loud:

• 1) The leak rate on my Aura and Swift are around 25 liters/min. Thats a lot of air going out of the vents.
  2) When I inhale, the machine speeds up to supply enough air to maintain 9 cm of pressure and supply my air intake. Air continues to flow out of the vents because there is 9 cm of pressure in the interface.
  3) When I exhale, the machine slows down because I'm not using any air and it is still maintaining 9 cm of pressure. Actually, the pressure subsides somewhat due to the C-flex feature that reduces pressure on exhale.
  4) The noise level of the interface and machine are less on exhale. This is bothersome because with normal breathing, the noise on exhale is greater than on inhale, for me anyway. [Not germane.]
  5)Okay, where am I going. I'm not sure.
  6) But, when I'm exhaling, all of the air from my lungs and the air being supplied to maintain the C-flex exhale pressure is being forced out of the vents. That is, the entire air flow is going out of the vents.
  7) Now, I suppose the question is, is there a sufficient flow of air to carry the exhaled air out of the vents?
  8 The Aura nasal seal has a volume of about 30 ml.
  9) Well, with a flow of 25 liters/min (25,000 ml/min) continuous. During a 3 sec exhale, 1250 ml is being exhausted. I'd bet that the 30 ml volume of the Aura nasal seal passages is completely refreshed during exhale.
  10) One poster pointed out that if the location of the exhaust ports didn't matter, the manufacturer's might put them on the machine or on the hose well away from the interface. Might be a problem with this because the entire hose volume would then have to be expunged during an exhale.

Anyway, this is my seat-of-the-pants thought on the matter.

The only time my Aura gives me a headache is when I drink too much alcohol before going to bed.

[Jerry69]

I was curious, so I filled the 6-ft hose with water and poured it out. It only holds 600 ml. So, the exhaust during a 3-sec exhale (1250ml) will expunge the hose and the nasal seal, easily, as they are only 20 + 600 = 620 ml.

If I didn't miss a decimal point, you will have plenty of fresh air to breath next you inhale. IOW, your headaches are being caused by something else.

Jerry

[MissAmethyst2U]

WOW, all I have to say is I read some of the stuff you ppl knwo on here as in Math and calculating all kinds of stuff and I am just amazed...I feel soooo lost half the time reading this stuff lol...I diff feel like I need to go back to school and I am one of the youngest ppl on the boards if not the youngest...

[john5757]

Jerry69

It is my understanding that with the Aura for example the exhale has to travel the same path as the oncoming fresh air that is under constant pressure to reach the vent in the opposite direction. The 30 ml volume of the Aura nasal seal will never get refreshed until you stop exhaling and some of that exhale can be re-breathed. If the Aura has a different path for the exhale breath to escape then the fresh air can reach the nasal seal and refresh it. If you can visualize the exhale as red and the fresh air is white and the vent is on the other side of the hose all the tube will be red by the time you reach the vent and some of the red exhale will be pull back alone with the fresh air when you inhale. If the vent is at a different location on the mask from where the fresh air is coming in you have a better wash out effect and the incoming fresh air has a better chance to refresh the nasal seal with fresh air. Generally not the best idea to put the vent on the supply line that is under constant pressure trying to keep the mask with fresh air.

[Jerry69]

Jerry69

It is my understanding that with the Aura for example the exhale has to travel the same path as the oncoming fresh air that is under constant pressure to reach the vent in the opposite direction. The 30 ml volume of the Aura nasal seal will never get refreshed until you stop exhaling and some of that exhale can be re-breathed. If the Aura has a different path for the exhale breath to escape then the fresh air can reach the nasal seal and refresh it. If you can visualize the exhale as red and the fresh air is white and the vent is on the other side of the hose all the tube will be red by the time you reach the vent and some of the red exhale will be pull back alone with the fresh air when you inhale. If the vent is at a different location on the mask from where the fresh air is coming in you have a better wash out effect and the incoming fresh air has a better chance to refresh the nasal seal with fresh air. Generally not the best idea to put the vent on the supply line that is under constant pressure trying to keep the mask with fresh air.

John, I'd like to be able to color my exhale red, or inhale some smoke (not cigarette, ugh) to see how it clears from the nasal seal. If I could find something suitable to inhale through my mouth and exhale through my nose while holding a hand mirror, I could see the dispersion of the exhaled air. [If you can think of anything, try it, and if you live to tell me, I'll try it. ]

The Swift design does seem to have a better washout path. However, I suspect the Aura vent acts like an eductor to eject air from the nasal seal tubes.

Barring any testing such as I described, I'll just have to go by the way I feel. I've been using the Aura for several weeks, now. and prior to that, the Swift and Breeze, mostly the Swift. I don't notice any difference, except that the Aura is more comfortable, but nothing that I could attribute to re-breathing CO2. (I frankly don't know what the effects would be.)

Jerry