Guys I would quit trying to tell him he's wrong. We all know he is, but he will not accept that fact. And you're saying this right after Sludge posts data confirming my observations? The dotted line on the graph above shows that the inspired air in this mask never falls below 1% CO2 during the brea...

Several people have commented that a vent rate of 20-30 L/min should dilute that CO2 to a much lower level than what I am seeing and that therefore I must be wrong. Actually I'm with the crowd that's saying your entire testing methodology is wrong. Your graph indicates that your FECO2 - FICO2 diffe...

miltf I think I see the measurement error in your procedure. When you exhale, the pump sucks in air from your exhalation and you see a rise in CO2 concentration. When you inhale, the enhanced CO2 level air still remains in the sampling tubing and is only gradually mixed with the incoming air from t...

One more time -- I have an S9 Auto. It starts at 5 cm and then goes up (to about 10) as needed by my breathing. Why the bad vibes?

Thanks for all the responses. Here is the data: http://i1369.photobucket.com/albums/ag239/miltfriedman/co2cpap_zps8c1cc22b.jpg As you can see, the level of CO2 never drops below 2.2% or so, so it doesn't matter what the deadspace volume is, I'm still breathing 2% or higher CO2. I may be a pretty sha...

According to this study: http://www.archbronconeumol.org/en/comparison-of-carbon-dioxide-rebreathing/articulo/13087086/ your readings are a bit low... Thanks for the observation. This is one of the only studies published on CPAP rebreathing and it points out that placing the vent on the elbow or tu...

I don't have a mechanism for why I get congestion -- I just know that I don't get it when I don't use a silicone mask. I can certainly smell the silicone though so it must have some volatile content. As to other details -- The air in the mask is sampled through a flange fitting in the mask wall. A v...

I don't know how to post the graph, but basically the CO2 level in the mask goes up to 3.3% when breathing out and down to 2.3 or so after breathing in. The sampling point is in the mask deadspace, not in the hose. The CO2 level of air entering the lungs during breathing is somewhere between these 2...

Hi, This is my first post here. I am a relatively new CPAP user (6 months). Initially, I found that the silicone in most masks gave me nasal congestion, so I switched to Sleepweaver masks which are cloth. No congestion, but I sometimes had a shortness of breath feeling. I thought maybe the fixed ven...