1 day of data on each machine is not enough information to make a definitive decision on whether one machine is significantly better at treating your apnea. The AHI can vary (quite a bit) from day to day, even when using the same machine night after night.
That said, there are a couple of relevant things in your post.
First, you say:
Quote:I was then given a Philips Dreamstation auto to try, I found this machine so much more comfortable as it didn't overwhelm me with pressure, and I preferred it over the Resmed
In the long run, you may be much better off with the Dreamstation because the first thing that has to happen for PAP therapy to work is that you have to actually be able to sleep with the machine all night, every night. Comfort issues are very important and it seems that the steep pressure increases in the Resmed bother you quite a bit. And that could make it more difficult to really learn how to sleep well with the machine.
Next, let's talk about the AHI's: First, each company does have it's own proprietary system for scoring the data recorded by the machine. The differences are usually not enough to make a huge difference, but it's possible that the DreamStation is scoring OAs and Hs just a bit more aggressively. But that would not account for the huge jump in AHI: If we look at just the OAs + Hs (the obstructive events), the DreamStation did let a lot more events get through. But it also looks like you only turned the DreamStation off and back on two times during the course of the whole night. But you turned the Resmed off and back on four times during the night you used it. So it looks like your sleep may have been a lot more fragmented on the night that you were using the Resmed. And if you didn't sleep as soundly or as deeply, that could explain why the AHI is much lower---many people's apnea is much worse and needs more pressure to control during REM sleep for example.
As SleepRider and OpalRose both point out, there are a lot of centrals being scored on both nights. More pressure usually does not make centrals go a way and more pressure can make them worse. Whether these centrals are "real" is a big piece of the puzzle. And that brings up the question: Were central apneas mentioned on either your diagnostic or titration sleep studies?
Some new PAPers do have a tendency to develop CAs once treatment begins. Sleep docs usually take a cautious "wait and see" approach. The reason why is pretty simple: The excess number of CAs scored for for many of these newbie PAPers disappear on their own as the person's body fully acclimates to sleeping with the PAP. Most sleep docs would be willing to investigate what's going on if the CAI > 5.0 after a month or two of therapy. At that point, a titration study on bilevel or ASV may be recommended.
Here's what I would recommend that you do:
1) Download SH 1.0 now that it's available and look at the DreamStation data in SH as well as Encore. It's a little bit difficult to compare an Encore report to a SH report because Encore doesn't show the flow rate data.
2) Keep the DreamStation since it's more comfortable, but increase the min pressure by 1cm. That might be just enough to help the less agressive PR Auto algorithm respond fast enough to keep clusters of events from happening.
3) Schedule a follow-up appointment with your doc if you don't have one already scheduled. Let the doc's office know that the AHI is mainly composed of CAs on both machines.