How to setup System One Auto BIPAP BiFlex as an Auto CPAP?

Thinking of using a used Auto BIPAP Biflex (750P) as a backup CPAP. I am sure there are many advanced users of BIPAP here, so here are the knowns and unknowns

At present I am using an auto with this settings:
A-Flex=1
Min Pressure: 6
Max Pressure 10
and get pretty good results in the last 5 years

If I use the BIPAP Biflex auto , how to setup this settings into the System One BPAP Biflex auto, so that it can behave as a normal System One auto?
IPAP=10 ?
EPAP=6 ?
PS=?
Biflex=1?

Please let me know -

You can't make the BiPap Auto behave like an APAP. You can get close but the BiPap has a 2 cm default pressure support that you can't get around. It can't/won't go any lower. To have it behave like an APAP you would need EPAP to equal IPAP and let IPAP have its range up to whatever maximum you set.
To get close to APAP settings you would need EPAP at 6 cm and Max IPAP at 10 cm and PS of 2 in auto mode.
Doesn't matter what the BiFlex setting is. That's a comfort feature and it doesn't really matter but if you liked AFlex at 1 you probably would like BiFlex at 1.
The ResMed S9 VPAP Auto will allow EPAP to equal IPAP but the Respironics machines won't.
Your APAP settings were pretty tight and using EPAP 6...IPAP max of 10 with PS of 2 should be real close and be comfortable for you. While awake you will see EPAP at 6 and IPAP at 8 and when you go to sleep the machine will do its auto adjusting as it senses the need.

Hi Pugsy

thank you for your very informative guide. I will try your suggested settings tonight and see how it goes.
I like the idea of having this BIPAP as a backup since it can be used as an all-round CPAP and I bought it used at a very great price.

What I noticed from the SleepyHead reports is that I experienced Clear Airway apnea every night. I guess this is the same as Central Apnea and am concerned. When using S9 Auto, my results are consistently very good: AHI less than 1 however with BIPA my AHI is around 2 and I have CA of around 0.2

Is this something serious?

No, nothing serious with the difference in AHI or Centrals (Clear Airway).
Different brands and different ways of doing things and slightly different definitions too.
The difference between an AHI of 1 or 2 is insignificant anyway. With time you might find that the BiPap data trends downward. I had that happen when I started using the BiPap last year. Over about 6 weeks the AHI reduced by 50% overall without my changing anything. You will likely see some nights a little better than others but unless you get up to the 4 to 5 AHI range and stay there...I wouldn't worry.

Just get into the setting menu and found out that I can only set PS =3, 3.5 and 4

Well 2 cm is the default and not much difference between 2 and 3 anyway. With such a tight range with max at 10 cm it isn't going to make a huge difference anyway. PS will roam around between 2 and 3 when asleep as needed.

Thanks Pugsy
Will post the sleep results later after 3-5 days to see the trend and whether CA is still there

I find I have some nights with minimal to none Centrals and then other nights it looks like central city convention.
Almost always in clusters which can be explained away with "awake" stuff being flagged. Occasionally no known explanation but as long as they don't start having conventions in large numbers every night I just chalk it up to aliens and don't worry about it. I have found that when I have a "bad" night being restless maybe from back pain or something I always seem to have higher central count. I suspect they are the turn over in bed hold my breath centrals.
My AHI varies each night anyway. One night it might be less than 1 and the next night pushing 3.0 AHI and I can't explain it. It just happens. I don't feel any better or worse with either night anyway.

well so far only 2 nights data. First night after the change of settings: very good, AHI less than 1 - the best so far and no midnight wakeup. The 2nd data last night: wake up at 1 AM and stay awake for 2 - 3 hrs and AHI 2.2 - the worst so far, due to large CA and OA. As Pugsy stated, many of the CA happened when I was awake.