Then, in December, since he'd been five years on the same machine, his DME switched him to the new Respironics DreamStation, with the same pressure setting of 6-16 cm.
Now, with the DreamStation, his AHI average is 13.2, with some nights over 20. I checked SleepyHead's numbers with Encore Pro to be sure, and they matched up.

As you can see, on Dec 24th he switched to the new Amara mask, and it worked well with the old System One machine.
On Dec 28th he switched to the DreamStation, and his obstructive apneas went from one or two a night to 40-80 a night. And his clear airway apneas went from 10-20 events a night to just one a month.
The main problem is that the DreamStation, in reading all these obstructive events, jacks up his pressure all the way to the max at 16 cm. This pressure not only causes all sorts of leaks, but wakes him up, and it's really frustrating him.
To top it off, all that pressure isn't stopping the obstructive events, as you can see here.

After the first few weeks, I printed up a couple charts showing the difference, and he left them at his sleep doctor's office, along with the information on his card, but after a month we hadn't heard back a word.
So I printed up more charts, and he took them and his card in to his DME. She said she couldn’t make sense of it, but she forwarded the information to both my father's sleep doctor and to Respironics.
She also suggested what I'd been trying to get him to do - to go back to his old machine for a night. That was March 7, which you can see in the first chart, where he had an AHI of 3.9, right where he'd always been.
Seeing that, she gave him a new DreamStation, in case the first one wasn't working right. But that night showed the same readings as before.
That was three weeks ago, and when my father called her yesterday, she said she hadn't heard back from either his sleep doctor or Respironics, but would contact them again.
The best I can figure, the DreamStation's algorithm is reading his events differently, with more obstructive events and less centrals. It's also reading less PB, so it might be labeling those events as obstructive events.

The RERA has also changed. On the System One it was nearly always between 2.0 and 4.0, and with the DreamStation it's nearly always between 0.2 and 1.5.
Also, and what might be key here, the obstructive events on both machines are nearly always not from long pauses in breathing, but periods of shallow breathing between deep breathing, as seen here.

He has this breathing pattern for a part of most nights, and when I brought it up with his sleep doctor a few years ago, he had my father wear an oximeter for a night. It said his oxygen levels were fine, so the doctor said it wasn't a cause of concern.
But it seems the DreamStation is seeing this same breathing pattern, marking it as obstructive, and trying to use extra pressure to fix it.
I'm sure his doctor would say that as long as he's sleeping well and getting enough oxygen, that's what counts most, and he'd be right. But it's very disconcerting to get so many AHIs, and my father says he'd really like to go a night "without having my mask explode."
So I'm hoping you can clue us in to what's going on and what we might be able to do about it.