I was diagnosed with OSA in 2004. I currently use a REMStar Pro with C-flex+. My PSG from 3/2010 showed an AHI of 0.6, but an RDI of 9.6. I subsequently had a titration study that resulted in a Rx of 5.0 cm H20 (I cannot current find the report).
A couple months ago I moved from 5200 ft to 1000 ft (the elevation my sleep study was at). At that elevation, I had it set at 5.5 cm as my AHI was not below 5 and the symptoms were obvious. After moving at the end of June, I still had it at 5.5 cm and my AHI gradually rose from ~3 to ~5 with symptoms returning. As I was starting to get symptoms, I started taking a closer look at my data by downloading SleepyHead. In doing this, I noticed I was getting some leaks that would correlate with my AHI increasing through the night, so looked into my Swift FX mask and realized I didn't have the straps optimally set and readjusted them. However, since doing so, my leaks have gone from 5-6 Lpm to 1-3 Lpm yet my AHI has climbed to between 4-5.
Here's more of a breakdown:

Sample:

At 7/21, was having symptoms still, so tried an increase of 0.5 cm to 5.5, everything pretty much stayed the same.
Sample:

Was still getting some high numbers which would correlate with afternoon exhaustion and sluggishness, so checked out mask fit and discovered I was wearing it incorrectly (velcro straps too high up, silicone strap too far back). I then had the results from from 9/1 to 9/4:
Sample:

I noted a decrease in leaks almost immediately, but also AHI jumped to the mid 4s with even more tiredness. Most notable are an increase in CA and HA. I thought perhaps I was getting too much pressure and then went back down to 5.0, my prescribed setting for 9/5 to 9/7.:
Sample:

It should be noted that for some reason I'm getting scored for obstructive events that last less than 10 seconds. On 9/5 it scored 9 events (4 of which were > 10s), 9/6 one 11s event and 9/7 had 7 events (one of which was > 10s). Now there's a big jump in hypopneas and I'm figuring an insignificant jump in obstructive events.
So, the trend I see is that my leaks have improved, but my AHI has worsened. Over this time, I've also noted that on nights where I have alcohol, my AHI can be very low - in the 0.9 to 1.5 range - obvious outliers, but I would think it would have the opposite effect. Looking at this data, it makes me wonder if my pressure is actually too high.