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Rebreathing / acceptable flow
#1
Rebreathing / acceptable flow
Is there a way to monitor rebreathing in sleepyhead / Oscar? Can you cross reference tidal with exhale volume or something and see how that compares with the force of port air? I'm on ASV for CSA, 

I have some masks that are my favorite, Dreamware Full Face, but I can't wear it. I get too high and have a slight drop in 02, end up getting a higher ahi even with a perfect seal.  I am on ASV, so my ahi is typically <0.5. Anything over 1 and I feel like garbage.  I notice this with the Dreamware specifically, and anytime I use the Quiet Air elbow on the f20 / f30.  I wanted to switch to the F30i, I noticed there are more port holes and you can use the ported elbow up top, but before I dropped $100 I want to see if there's a calculation I can do to figure out port volume vs pressure vs mask.   I know there is a difference in 02/c02 sensitivity in different people, but the F30 with the ported elbow is perfect for me. Just trying to get the hose off my face. For me specifically, the f30 liner sits a bit too high around the edges of my giant nose and I have to wear a breathe right strip to mitigate.
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#2
RE: Rebreathing / acceptable flow
In short, OSCAR does not do this, and I'm not aware of any software that can. Most masks have a designed exhaust rate at pressure, and we discuss that and rebreathing calculations in the EERS wiki. Perhaps that is a good place to start to learn how we calculate enhanced expiratory rebreathing space http://www.apneaboard.com/wiki/index.php...ace_(EERS)
Sleeprider
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#3
RE: Rebreathing / acceptable flow
I may be confused, but I feel like this theory/system does the opposite of what I would need. An increase of co2 would exacerbate a drop in o2, wouldn't it?  I guess the lack in o2 is what causes the body to want to breathe, but I'm finding the masks that port out more air are the masks that I generally feel better in. Something like the quiet air elbow, restricting more expelled air, which I would imagine is what the eeer/ system theory (can't see the name in the reply) does, increasing co2 / blocking the port?

**EDIT**

add
The apnea, believe it or not, is not really my issue. It's the drop in o2, which causes the headaches, nightmares, and dizziness. I feel like the eers build could make that worse.
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#4
RE: Rebreathing / acceptable flow
The CO2 is the one that causes a breath reflex.  If you reduce the CO2, the brain thinks it has enough oxygen and doesn't require a breath.
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#5
RE: Rebreathing / acceptable flow
Do you think that one has the opposite effect on the other?  Increase of co2 may fix the apnea, but causes a bigger drop in o2? Or am I thinking of it in the wrong way. It seems like the ahi is less of an issue for me because the asv catches me every time I fall anyway. But when I wear that quiet air and restrict the expelled air, my apnea is always higher. When I have the ported elbow my ahi is lower.
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#6
RE: Rebreathing / acceptable flow
Nothing is so simple. By rebreathing some CO2, the spontaneous respiratory drive is stimulated. This can reduce central apnea events and increase minute vent by improving both respiratory rate and tidal volume. The small amount of CO2 in re-breathed air does indeed displace some O2, but not much. The reason I pointed you to that wiki is so you can see exactly how we calculate volume of rebreathed air.

The problem of low SpO2 needs to be looked at individually, not as a function of expired air or mask exhaust rate. Nearly all masks are designed to exhaust 4 to 5 times your volume of inspired air. There is less expired air rebreathed with CPAP or your ASV than if you were using no therapy at all. The source of air is remote to your expiration, and the vent rate exhausts nearly all expired air exclusive of airway dead-space. So I don't think your choice of mask greatly affects the oxygen content of inspired air (FiO2).

If you seek to increase your oxygen saturation there are a few alternative ways to approach it. The most direct is to use supplemental oxygen. We wrote a wiki for Oxygen Bleed with CPAP to help you learn how to calculate the FiO2 from supplemental oxygen http://www.apneaboard.com/wiki/index.php..._with_CPAP

Another means of improving oxygen exchange at the alveolar level is to use higher "Postivie End Expiratory pressure" (PEEP). This is a well known ventilation tool, and improves oxygen exchange by increasing the partial pressure of oxygen in the lungs. PEEP is the same as your EPAP pressure, and increasing that not only reduces obstruction in the airway, but acts as PEEP and can improve SpO2.

Perhaps you can let me know why you are concerned with this topic and I can direct you to something more targeted to your interests.
Sleeprider
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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.
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#7
RE: Rebreathing / acceptable flow
I apologize for the unacceptable delay! My interests are self preservation ? .
I can find no easy way to monitor this, or know in advance with the kind of setup I’m using, (ie mask type, air flow/ports / vents etc) if whether or not my levels are going to be messed with/messed up. I’m obviously super sensitive to changes, just using the quiet air elbow on my f30 makes me feel unbelievably groggy and gives me a headache. I have a solid track record of 0.23 apnea average, with 0 leaks, on my ASV. And never feel the way I do than when I have the quiet air elbow or the dreamware full face mask.(Bad!)

It may sound like a ridiculous stretch, but even if I don’t wear the mask at all, on occasion, usually 1x a month, I don’t feel as groggy as I do than when I’m rebreathing air.
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#8
RE: Rebreathing / acceptable flow
While not directly addressing your question.  Below is an interesting thread on the Quiet Air elbow.  It is conceivable that the diffuser material has become a bit clogged over time and has made enough of an impact on on air flow that you are having adverse effects.  An easy test is to use a standard F20/F30 elbow and see how it goes.
 
http://www.apneaboard.com/forums/Thread-...r-Vent-F30

John
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#9
RE: Rebreathing / acceptable flow
I appreciate it, but even using a brand new Quiet Air doesn't work for me. I consistently feel like im rebreathing my air, always get headaches, and generally feel like crap, groggy and dizzy as im falling asleep, every time with the quiet air. Obviously the answer is to not use the Elbow, but more specifically im looking at exhalation of the original Elbow flow vs Quiet air, and the Dreamware mask vs the new Airfit F30i.  The dreamware also makes me feel dizzy and groggy every time. I've been on the ASV for almost 3 years, and always fall asleep with no issues, and wake up feeling fine. It's only the QA elbow and the Dreamware, which I feel like every time doesn't allow me exhale properly, consistently breathing in my own air. I'm looking at the instruction manuals for both masks, the Dreamware and the F30i (specifically the "I", new one) Just trying to figure out if it'll be worth it to buy the f30i, since I aready have issues with the DW.  The F30i already looks like it has more exhale/port holes in it vs the dreamware, which is good in my case. Couple that with if I use the original elbow, I feel like I should be ok.
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#10
RE: Rebreathing / acceptable flow
I have no idea if this helps, but I think you can find venting flow in L/min for different masks at different pressures. Have no clue if that even applies to your exhaling pressure, but maybe you can see the numbers and glean something from them.

Just google the mask and look for a user guide or manual and go to the technical specs.

John

Edit Added: I did a quick look and at a pressure of 30, the F30 was close to 70 L/Min and the DreamWear was around 50 L/Min. Beats me how that translates to the real world.
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