I am a bit of a newbie myself (got APAP on Sept 20th) and am not currently using a pulse oxy meter (though I would love to!).
Question for you - in the post itself you list the S9 Auto 25 but in the profile it lists the S9 Elite; the S9 Elite is a straight CPAP whereas the S9 AutoSet automatically adjusts breath by breath to deliver the lowest therapeutic pressure.
The machine being used will affect your treatment.
Also, I Highly recommend using the SleepyHead software; it is much more understandable than ResScan, at least for me (GRIN!).
I just checked the link for the SleepyHead (SH) software, at the top of this page, and here is the info on O2 compatibility:
##As of 0.9.8, SleepyHead works with the full range of Contec CMS50 series of Oximeters (and clones, like Pulox) either standalone or synced with CPAP data.
SleepyHead also supports ResMed and PRS1 oximeter attachments, and file import from ChoiceMMed MD300W1 oximeters.##
Evpraxia in the Pacific Northwest USA
Diagnosed: 44 AHI when supine, O2 down to 82%
Treated since 20 Sept 2014:: 0.7 AHI, Settings 7-15, EPR on Full Time at Level 3
Better living through CPAP/APAP machines!