Found this, which I thought was interesting:
http://www.ncbi.nlm.nih.gov/entrez/quer ... t=Abstract
Given the above, (and I think this is what was being suggested) the different masks might have just enough different resistances that they would cause disturbances.
I also wanted to understand the masks you were using; I think you did poorly with this one
https://www.cpap.com/productpage.php?PNum=1717&PAID=215 and this one
https://www.cpap.com/productpage/Comfor ... -Mask.html
while this mask works well for you:
https://www.cpap.com/productpage/resmed ... ystem.html
I am not a medical type, but I was a scuba instructor. Were someone doing a dive and had they said, "Gosh, I couldn't relax and now I have a headache," I would have suspected hypercapnea (CO2 retention) which would cause both the tension and the headache and would have asked if they were forcing a deep breath occasionally to flush their lungs. Breathing while diving changes your buoyancy - by about a pound per pint of air - so people take shallow breaths so that they can maintain a vertical position in the water column. This turns out to be a bad habit - you need to breathe, as we all know.
Of course, you can't consciously take periodic deep breaths while you are sleeping, but one thing that I really think about is both retained dead space and the way the mask ventilates.
I actually thought I had better nights with the old nose mask if it leaked a little as long as the leak did not blow into my eyes - my thought was that the leak flushed the exhalation out of the mask.
I only own one of the masks you mentioned - the Swift. One thing I have noticed about it is that it just flat DUMPS air out those little holes - my old mask had a section of hard plastic tube with some angled cuts in it, and, well, it sort of leaked a little air by comparison. And the leaks were out past a fairly large tidal space - not a huge space. I sometimes wondered if it leaked enough volume to clear the tube of rebreathed air.
I have no such worries with the swift - in fact, sometimes I feel like there is almost too much air dumped. The swift also has the holes right near the nose piece - meaning that there is almost no additional unventilated tidal volume.
The swift also seems to breathe freely. How do the other masks compare in regards to dumping exhalations, free breathing, and unventilated tidal volume?
When I first started this, I was told that there were two alternatives for exhalation air - one was a valve that was set to your pressure and which would dump when the circuit went overpressure - which would happen when you exhaled.
There was a bit of hysteresis in the valve - that is, the pressure to keep it dumping was not as high as the pressure to open it - and then, as soon as you started inhaling, that allowed the valve to "snap" shut and completely seal.
I was told that those valves were technically better - but fragile and not usually recommended because of the fragility - or the fact that a little dirt on the sealing surface would cause them to leak, and no matter what they died after a year or two. I don't see anyone selling anything I recognize like that at all these days. Also, they needed constant cleaning.
The other was the type I had where there were constant dump slits.
Now, back to the Swift - I also believe that it is an irritating nose thing to use. That hose hanging off to the side is sort of odd. It tends to blow air right in your nose and all that, and to blow hard. The first night, it was incredibly comfy, and then, well, frankly, it got less comfy. I'm find I'm blowing an interesting and colorful assortment of ooze out of my nose in the morning. I find that changing the nose piece to one that is a different size every couple days helps. All that is to say that I really understand why you want to change out of it after a few days,
But I can tell you that the way I sleep with my nose mask and with the pillows seems different. If they could titrate you endlessly, it might make sense to try you in different masks - but there is a payback point.
If this makes any sense to you, then you might look at the masks and decide which ones have a larger unventilated tidal volume. Try leaving a tiny leak to make the whole mask ventilated. Maybe, if you have a teeny tiny drill bit, you could make a teeny tiny hole that would allow more of the mask to be ventilated - if it is a bad idea, you can probably patch the hole with a bit of paper and some superglue. If it is a good idea, you might try plugging a couple of the holes in the mask and making some holes where more of the mask is ventilated - so that you end up with more or less the same leak area and a better ventilated mask.
Different people really are more or less sensitive to retained co2. One of the good things about those old Mike Nelson two hose regulators is that they inhaled from one side and exhaled from the other (and when Mike cut the bad guy's air hose to disable him, he always cut the exhalation side) so you were breathing in hardly any of the air you breathed out. But this big old regulator that sits in your face, well, you inhale and exhale through that same volume, and it means that there is a regulator full of exhalation you are gonna inhale - and the exhalation is probably only 10% O2 rather than the 21% you breathe in. And that little bit of air, well, it has the CO2 you just exhaled - and you breathe that in too.
Some people didn't notice the little extra CO2 - most people didn't - but some people were sensitive to it.
There were low volume regulators, and sometimes a change to a low volume regulator would cure post dive headaches - just because the diver would be pulling in less air that they had just breathed out. Good luck.
