? on hose and mask

[Sleepless in Indiana]

I am a new hose-head so still trying to figure it all out. My question is related to only breathing fresh air, instead of rebreathing the same air. I was given a F&P Flexifit 431 mask to start with, and noticed that it has a small fitting that is between the hose and the mask elbow, that has what I would call a reed valve to keep the air you exhaile from going back up the hose. I just got a ResMed Mirage Activa LT nasal mask, and it doesn't have anything like a check valve. I think I can tell that some of the air I breath out goes up the hose, and then as the C-Flex comes back up, I can feel a second or so of hot air coming back into the mask before I get good fresh air. Am I missing a piece or is this normal? I don't really feel much hot air dump out of the mask opon exhaling, like I did with the full-face mask.

Any ideas? - Thanks

[TheDreamer]

The 'check' valve on the full face mask is more likely the anti-asphyxia valve, which isn't 'needed' on a nasal mask. Because if the PAP goes off during the night, you'll hopefully open your mouth and keep breathing with the nasal mask. While a full face mask needs some way to let air in when the pressure drops.

Otherwise, the masks rely on positive pressure to blow your exhale out of the exhaust ports to avoid rebreathing.

The Dreamer.

[Bearded_One]

Depending upon the type of mask, there is usually a small amount of exhaled air left in the mask, and as long as the exhaust port isn't defective or obstructed, there isn't any danger from rebreathing that small amount of exhaled air. Nasal pillows have virtually no air left in the mask between breaths, nasal masks have a very small small amount of air left in the mask between breaths, and full face masks have the most air left in the mask between breaths.

[roster]

The Resmed Activa LT nasal mask has exhaust ports that are large enough to prevent buildup of excess CO2. As long as you don't block those ports you should not worry.

I have what may be a bigger concern for you. You say they originally gave you a full face mask (Flexifit 431). This is usually given to someone who mouth breathes or leaks during the study.

Now you have switched to a nasal mask. If you are indeed mouthbreathing/leaking, the pressure will escape and the airway will not be held open - you still will have apneas.

Do you know why you were originally given a full face mask?

[Sleepless in Indiana]

I did the split study. So after 2 hours of sleep, they put me on the machine. They tried the nasal mask at first, and I laid there for over 30 minutes just listening to the sould ofthe machine and couldn't go to sleep. I felt ok, and think I was just concentrating on breathing with the new adventure of Cpap. They said I was breathing slower then I had been. So they switched me to the FF before I ever went back to sleep.

I have been watching my numbers and they seem to be just about the same with either mask. I think the leaks are less with the nasal mask. And I seem to be not wakeing up to loud leaks. I seem to be able to seal my tounge to the roof of my mouth very easily ( as I have an extreamly narrow pallet). So I thnk that is helping me out. But have seen from reading all the post on here, that I need to keep a watch on this issue. - Thanks