Breathing in what you breathe out?

[Chronitia]

I am brand new to CPAP, I've had mine for less than a week. There is something that I experienced a bit during my sleep lab and that I am very much experiencing now. That is, the feeling that I am breathing back in what I just breathed out. Maybe it is an illusion, but I tend to breathe without much/any pause between in/out with the mask on. So often my breath in will feel hot and humid and not refreshing at all. I often have to take another quick breath right after it. It feels like I am breathing in my own stale exhalation out of the mask and not getting any oxygen. I have C-Flex at max level because it makes exhale much more comfortable; could it contribute to this feeling though? My pressure is at 10...seems like it should be enough to quickly push my exhale out of the dump valve?

Anyone else have any experience or tips with this? Should I try turning c-flex down/off?

Thanks!

[Wulfman]

What about your humidifier? If you're using heated humidity, turn it way down or off.

Den

[Chronitia]

Yeah, I started at 3, now I'm down to 1. The normal temp/humidity of the air isn't a problem. If I force myself to hold my breath for a few seconds between exhale -> inhale, I get cool dryish air. The problem is with the mask on I'm always either breathing in or out, and often I'm breathing in what seems to be an exhalation.

[Wulfman]

I've never used a nasal mask, so I think I'm out of ideas on this one.
I would think a pressure of 10 should be able to flush out the CO2.

Den

[crossfit]

Is there anything blocking your air vent? I sometimes notice that feeling when the covers are up close around my face. Other times I just put my arm up near my face to feel the air coming out of the vent to reassure myself. I also found it more of an issue when I had my Aflex on 3. On 2 it seems to be better. I tried it at 1 and it felt odd.

[Julie]

If you're using the ramp feature (starting at e.g. 4 or 5) you may just not be getting enough air period. You might try not using the ramp at all and just go straight to your proper setting.

[Chronitia]

Thanks for the responses!

In regards to the ramp issue, I've tried that, but the problem still happens when I'm at my max pressure.

The vent is definitely not blocked, I feel a strong push of air out of there.

Thanks for confirming that the A-Flex might be part of the issue...I'll try dropping it to 2 like you did and see if it helps; if it isn't enough, I'll try 1. Here's hoping

[feeling_better]

I am brand new to CPAP, I've had mine for less than a week. There is something that I experienced a bit during my sleep lab and that I am very much experiencing now. That is, the feeling that I am breathing back in what I just breathed out. Maybe it is an illusion, but I tend to breathe without much/any pause between in/out with the mask on. So often my breath in will feel hot and humid and not refreshing at all. I often have to take another quick breath right after it. It feels like I am breathing in my own stale exhalation out of the mask and not getting any oxygen. I have C-Flex at max level because it makes exhale much more comfortable; could it contribute to this feeling though? My pressure is at 10...seems like it should be enough to quickly push my exhale out of the dump valve?

Anyone else have any experience or tips with this? Should I try turning c-flex down/off?

Thanks!

There are a number of factors that can vary here, and you may indeed be breathing back in SOME of the air you are breathing out. I will try to go over these factors in detail below.

1. Your breath feeling hot and humid might be more contributed by a humidifier than anything else, although a small temperature increase will be there by the machine pumping in the air for you, even after you turn the humidifier off completely. Even when the humidifier is off, if there is water in it, there will be some amount of pass over humidification added. So try with no water, and the humidifier turned off.

2. But there is indeed some breathing back in. Almost all mask designs are such that all your out breath is not washed out completely thru the out venting port before you start breathing back in. The higher the pressure, more will be washed out. The higher the intended leak rate of the mask (this varies by mask model, even for a given pressure), more will be washed out. In addition to the leak rate, there is a 'dead space' for each mask. This is usually the volume of air in the mask from tip of your nose to the out port; which varies from mask to mask. The lower the dead space, more will be washed out.

As you observed, if you wait longer before taking a new breath in, more will get washed out. So there are a number of not so obvious, interacting factors in play here. The net result is that you are breathing a portion of the air back in.

Generally, this is not at all bad or harmful. But you may be particularly sensitive. You may want to try another mask, which has factors above which increases the wash out rate (more leak, less dead space, the outport closer to your nostril). You may also want to try increasing the pressure a bit.

3. Cflex settings, and the cpap tube length also affects the wash out! At the higher cflex setting (where the breathing is easier, especially for people who are new to cpap therapy), there is less wash out! This is because as you breath out, the machine reduces the pressure, so more of your breath will flow back into the tube and get mixed in with the rest of the air in the tube. The longer the tube, there is more compliance in the air in the tube ('springiness of the air'), this effect would be increased.

You can try decreasing your cflex setting or turning it off completely to see if your feeling you mentioned changes. But then again lowering your cflex might make it more uncomfortable to breath out, and you have another 'feeling factor' coming into play here...

Is lack of complete wash out of the breath good or bad? This is an interesting question, it turns out. Generally, if the out breath wash out is decreased, the oxygen saturation might decrease a little bit. However For some people who have Central Apnea (high H reading), if the CO2 washout is decreased, the H reading may come down -- so for these people the breathing in of part of the breath may be better!! Remember, with cpap therapy we are already increasing the air flow in so there is a more than normal wash out of CO2, and that is one of the causes of the higher Hs in those people.

So Chronitia, there are a few things you can try to vary here and see if it helps. If your try any of thee, we would be interested in hearing back from you.

[DreamDiver]

I don't use ramp because I makes me feel like I can't breathe.
Why not try turning off the ramp completely?

If that doesn't help, I wonder if you could try it without C-Flex.

[Chronitia]

Thank you very much for the reply!

I like this mask so much in every other way, would be a pain to try another one. If it continues to be a big problem, I'll try to find one with those factors you mentioned.

I've turned off the ramp and also turned down the c-flex, and that seems to help quite a bit.

I wasn't able to wear it most of last night because I was sick, I'll re-post here as soon as I have some all-night results.

Thanks again!

[carbonman]

I've turned off the ramp and also turned down the c-flex, and that seems to help quite a bit.

I found that when I turned off the ramp, it was much faster to get comfortable w/the
pressure. I have aflex set at 2 and it only takes a few minutes to get my
breathing relaxed and in sync w/the machine.

Every night when I get my mask on and connect the hose and reach for
the switch, I say, " ok, bring it, I'm ready".

[Chronitia]

Yeah! I'm doing without the ramp now. I have the c-flex turned off. And the co2 problem seems all but gone, but the extra pressure is causing some weirdness. I'll try a c-flex of "1" tonight and see if it's a happy medium.

[gasp]

I am brand new to CPAP, I've had mine for less than a week. There is something that I experienced a bit during my sleep lab and that I am very much experiencing now. That is, the feeling that I am breathing back in what I just breathed out. Maybe it is an illusion, but I tend to breathe without much/any pause between in/out with the mask on. So often my breath in will feel hot and humid and not refreshing at all. I often have to take another quick breath right after it. It feels like I am breathing in my own stale exhalation out of the mask and not getting any oxygen. I have C-Flex at max level because it makes exhale much more comfortable; could it contribute to this feeling though? My pressure is at 10...seems like it should be enough to quickly push my exhale out of the dump valve?

Anyone else have any experience or tips with this? Should I try turning c-flex down/off?

Thanks!

I have an A-Flex and have it set on maximum exhale relief. Even so, when first began therapy thoughts of my breathing rhythm entered my mind. Perhaps you're experiencing this kind of thinking? Before having a mask strapped to my face, the rhythm of my breathing wasn't topmost on my mind. I too wanted cool refreshing air, not the heated air sponsored by the humidifier. I got used to it quickly (probably a few weeks) and now don't think about it. I hope you get to this point soon : )

I'm uncertain, but I think the 'dump valve' takes a certain pressure that would be unique to an event such as aspiration. I could be wrong.