What is the Resmed ST used for and why would I need it?

[PappaJoe]

I have come across a resmed ST.  
It seems to give control over breathing cycle.
I seem to struggle with I:E ratio and thought this might help.
I struggle with very fuzzy flow rate too.
Unfortunately, attempts to include the ST into my therapy has resulted in Central Apneas in mass.
Any suggestions on how to dial in this monster would be appreciated.
Any explanation on the STs application would be appreciated also.
Thanks in advance for your response.

[SarcasticDave94]

The ResMed ST is a bilevel Spontaneous Timed machine. It's mostly used for patients with lung disease.

Yours however seems to be a hacked machine that acts like all somewhat, but will not deliver 100% like the actual higher level machines. Why I say hacked is due to your OSCAR chart states an AutoSet having ST mode, which is definitely not available from the factory.

In your many other threads you've bounced to considering many machines including VAuto and Philips Respironics SV Auto. I have lost track what you need, but I'm pretty sure ST isn't the right one. Let's find out if it's right.

Tell us what lung disease you have. If none, my opinion another machine or in the case of this suspected hacked machine, another mode is better. Probably just VAuto basic bilevel. Do note if it truly is hacked, it may not be as effective as the actual machine it's pretending to be.

[PappaJoe]

Thanks, Dave.
I hope that you may be able to set me on the right track.
I have COPD.  No other medical condition that requires special equipment that I am aware of.
Unfortunately, the years have not been kind so the ability to concentrate lags the ever growing curiosity about anything affecting my health; but I must keep trying to keep from dying!
Untreated sleep disordered breathing seriously affects my health, that's for sure.
(Before PAP therapy, you wouldn't have wanted to be near me driving down the highway.  And it's likely the afib surgery was necessary due to lack of PAP.)
Sleep study had me in the high 50s which scored a Airsense 11 CPAP in Aug 2023. (13 cm h2o EPR 3, changed to AirCurve 11 Vauto this January with a cryptic "Ipap setting 18/13 Epap 9/5" apparently the DME didn't know what that meant either because the machine came set to Vauto!)
Anyway, I've watched videos and read articles and comments esp on this platform and have learned that getting a machine is just the beginning.  That's where the medical establishment leaves off.  Instead, we must be proactive if we are to get to the most effective PAP therapy.
I have gleaned from my studies that the answer is in the fine tuning.
So, I've fine tuned CPAP (with and without autoset), BiPAP S and Vauto, ASV, BiPAP ST (modified Airsense 10) and some others one off.  It's been a waste of time and money and if anything has been concluded for all this, damned if I know what that is.  Still have the fuzzy FLOW RATE that I started with, no matter the machine or configuration. 
Don't know which way to turn.
Don't know if 'the fuzzy' flow rate is of significance anyway!
Don't know if the I:E ratio is causing CO2 buildup resulting in frequent arousals'. 
Do know that I'm not as rested in the morning as should be.
Can you offer direction, Dave?

[SarcasticDave94]

COPD would be one such reason for the ST. However it's rather basic in therapy delivery, except for the backup breath rate. It's static exhale/EPAP and inhale/IPAP with PS between them.

The modified CPAP you have is going to deliver somewhat compromised therapy in most modes, especially higher level ones. It seems to miss a bit of therapy accuracy.

Your current chart shows a recurring Unclassified Apnea event pattern. It may be Positional Apnea based, however you have Hypopnea as well so there's a need for higher EPAP at minimum. Again, the shortcoming of an ST is that you don't get variable pressures but static. This can't be set for ranges in EPAP or IPAP.

If you're able to try it, I would increase EPAP and IPAP by 1 each and see if it helps.

And I'd be less concerned over the flow rate look at this time.

[PappaJoe]

Thank you, Dave, for the speedy reply.