robertverhey wrote:But the real problem I've encountered (and I was surprised that it hasn't been mentioned by anyone else in this informative thread) is one of its design features, to maintain the high prescribed airflow rate (in my case 10) when two apnea episodes occur within one minute. This means that for the rest of the night it doesn't return to the base setting (in my case 4). This must be happening in my case, because I have woken up a few times now with the thing blasting away at full speed (well, 10) and the aforementioned dry mouth. 10 is enough to force my mouth open, even though I'm not normally a mouth breather.
That's the algorithm at work and the reason that it probably hasn't been mentioned before is that for most people that new minimum the algorithm comes up with because of the 2 apneas within a certain time frame is really a good thing and not necessarily a bad thing.
I am using that same algorithm in my AutoSet for Her machine and I rather like it but then my new minimum doesn't blow my mouth open.
In fact I sometimes see upwards of 16 to 18 max pressures and I still keep my mouth shut.
But if you switch to cpap mode and a fixed pressure the 2 strike thing is turned off....but you give up auto adjusting capabilities which means you most likely would have to use a higher pressure all night but if reducing the max to 6 didn't make the AHI go up much...probably not a big deal in terms of therapy effectiveness results.
What happens with any pressure (and what you are describing can happen at any pressure even 6 cm for some people) is that air goes up the nose and proceeds down the airway and instead of going down past the oral cavity it tries to exit into the mouth because the back door closing off the mouth from the back airway is open and not closed. Air enters the mouth...lips are closed maybe but the cheeks might inflate and before long the only thing left is for the lips to open and the air pressure to escape and this will often wake people up. We call this chipmunk cheeks and it can happen at any pressure and in any mode of operation on any machine.
Sounds like you may have a potential issue with the reduction in humidity that using the Humidex humidity thing. While some people do well with minimal humidity...others don't and a person just has to decide how critical that feature is to someone.
For me...it would be a deal breaker for sure but others it's not an issue at all.
If you didn't have dryness issues with the other 2 machines...you may have your answer there.
Oh...the non tiny ResMed APAP machine with the 2 strikes feature...that machine has another auto adjusting mode that doesn't do the 2 strikes thing...
So it can be turned off and still keep the auto adjusting mode but it no longer changes to a new minimum pressure if 2 apneas happen within a minute....it goes back down to the original minimum.
I may have to RISE but I refuse to SHINE.