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You probably don't want to mess with your max setting. If you suddenly have more of an obstructive blockage that requires 16cm then if your machine is set to say 12cm then there's no way the APAP in auto mode can then ramp the pressure up to 16cm because you've fixed the ceiling at 12cm.

You can change your lower pressure to that close to the pressure that you need when you have your apneas. For some upping the pressure can reduce the obstructive apneas/hypopneas but then induce central apneas, so it's a balancing game. The more you higher your min pressure on APAP the less in theory you should probably see.

The reason why you still see apneas on APAP is that APAP isn't a magic thing to rid you of Apneas, it's there to ensure it can respond if it sees one. If for instance you have a CPAP fixed pressure at 12cm but you have an Apnea at 14cm then the CPAP can't do a thing to resolve it and compensate. With APAP if your min pressure is set at 12cm and you have an Apnea at 14cm then the APAP will see the Apnea and continue to increase your pressure to the top ceiling (Max Pressure set) to then try to reduce the Apnea. It will also stay at that high level for some time before reducing the pressure back to the Min pressure to ensure you don't suddenly get another couple of Apneas in quick succession. It could be that you rolled over onto your back, your upper airway has closed more forcibly and requires more pressure to splint it open.

The only easy way to tell how many Apneas you are getting would be to not be on the machine and go for a Sleep Study. Even if you were to put your Min and Max pressure settings down to the lowest setting (and I would strongly recommend against trying this) it could still pick up an Apnea and resolve it as you have additional pressure coming in.

Melinda wrote:I don't understand why apnea events still occur, and frequently, while using xpap.
I too get clustered events. Shouldn't they disappear all together with the use of an xpap machine?
If I set my machine to near it's lowest flow setting(for max too), would that be a good way of seeing how many apnea events I get without the use of xpap? I'd like to compare just how many events my current machine is stopping on average.

That's probably not a good idea. Too low a pressure probably won't hurt you any more than not wearing the device at all. It's just counter-productive.
Here's a graph of what cpap therapy is like for 'ideal' user with a titration of 10.5. In the case of APAP, think of the pressure shown here as the minimum pressure. AHI decreases the closer you get to the sweet spot at the bottom of the bell curve. There is also the consideration of aerophagia. At some point it starts waking you up as much as apnea might, at which point you have to back off the pressure. Somewhere between the lines for aerophagia and apnea numbers there is an ideal pressure that gives the lowest number and duration of apneas with the least amount of aerophagia. This a very simplified example, and it isn't perfect, but it gives you a better idea of what to expect from obstructive apnea and why they titrate you. The sweet spot is different for everyone. Yours depends on your titration. It could be 7cm H2O, or it could be 17cm H2O. It's very unlikely to be 3 or 30. There are probably other limiting factors, but this simplified example gives an idea of what's involved. Since you've already been titrated, going to one extreme or the other will not yield useful information. There will always be apneas. We just have to minimize them as best we can.


(Note: for those smarties out there, please help me correct this if it's wrong. Cheers.)

dave21 wrote:I too find it interesting that we're self titrating even though we're on auto machines.

That goes back to the primary deficiency of "auto-titrating CPAP" machines. Left on their own, they allow unnecessary events. But used as a tool to home in on the optimal pressure, they work great. You've demonstrated that your numbers get better as you narrow the range around that "sweet spot". The logical conclusion of this narrowing would be straight CPAP at that setting. That's where I get my best results. (For the record, I don't "drink and sleep"; and I try to keep my other sleep patterns/conditions as consistent as possible.)

As others have said, you've done a GREAT job of explaining and documenting the process!

DreamDiver wrote:(Note: for those smarties out there, please help me correct this if it's wrong. Cheers.)

That's how I understand it too DreamDiver.

LinkC wrote:As others have said, you've done a GREAT job of explaining and documenting the process!

Thanks, hopefully this will be a good learning thread for many newbies to come!

DreamDiver, that's a great diagram. I would only add one note. ( I don't know if I'm one those "smarties", all I can add is from my own experience and research. )

It's my understanding (from talking with sleep techs over the years) that - if time allows - once they find that "sweet spot" they will try a pressure that's 2 to 4cm H2O over that sweet spot. That way they know if you can tolerate a higher pressure, if it is needed. But due to potential problems with central apneas and aerophagia, most doctors will prescribe the least amount of pressure needed to address the problem.

Hope that helps.

This could be one of the main reasons why a lot of sleep doctors prefer fixed pressure machines over APAP's due to the pressure could run away and create more central apneas and aerophagia in some patients.

I guess that could be considered quite a major downside for APAP's if the machine isn't set up correctly over a fixed pressure machine requiring potentially more visits to the sleep doctor, closer monitoring when it's just easier to provide a fixed pressure and leave it at that in the sleep doctors mind.

Dave,

Thank you for your incredible email. A few other forum members have suggested to me that my starting pressure of 4 is too low, considering my average pressure is 10.1. After reading your emails, I went and checked a week of data that was printed out for me a few weeks ago, and I studied it closely.
It seems that my apneas seem to happen when the pressure is at its lowest, ie around 4 -6.

I will be discussing this issue with my medical professional asap, because although my AHI has dropped from 33 to 2.5 after treatment, I want a AHI of ) !

Just a quick question concerning the graph. For pressures of around 18 and up it says no point titrating this high. My pressure sits at 18.5 at the 90% range, and regularly runs into the 19 20 range. Could this still not be titrated?

Is it possible for me to change the pressure on my vantage s8 autoset? I was under the impression this coulod only be done by the RT.

Here ya go, puffer:

Brenda's post:
viewtopic.php?t=22776

My post:
viewtopic.php?p=226375#226375

Wow, that easy, thanks gal. I might lower my minimum pressure from a 6 to a 4, just to see if I could get a bit more out of my battery on camping trips. The thing is, I get the feeling that my machine is not really really ramping up that much. Does anyone know where I can still get a card reader and software for this machine. My local RTS are practically of no help to me at all.