What brought me to this thread is that I am researching TiMin / TiMax settings. I have found this thread interesting because there are some similarities to what I am going through.
First, when I looked at the 2 graphs you posted on 3-14, one thing that sticks out to me is that on the zoomed in graph you had 3 episodes where the leak rate increased. Each one corresponded to a period without CA's.
This makes me wonder if you are getting too much air that is causing an imbalance of Carbon Dioxide (co2) and is causing your CA's.?
One big similarity is the issue of Insp time at 2.0. I have found on my data when I hit the TiMax it ends to lead to sleep disruptions with CA's.
I will give a brief summary of what I am going through and perhaps some of this may be of benefit to you.
I was diagnosed with OSA many years ago, but on the 2 previous attempts I was not able to become compliant with the machine. I just could not synchronize with it. I can not use CPAP, as I just can not exhale against the constant pressure. When I tried a bi-pap, when it forced an IPAP while I was tring to exhale it made me feel like I was suffocating.
So, we are up to current time, my 3rd attempt.
I did a mask fitting in Feb. The biggest change was the sleep lab started me with nasal pillows, to go with the least intrusive mask instead of going right to a full face.
Between the pillows and the new "easy breath" features, I was able to lay down and breath with the machine. I could even fall asleep with it!
For me it does not take much pressure to take care of my Obstructive apneas. 8/4 does it. The titration study showed 10/6 or 12/6 was "best", but I had problems exhaling against the epap pressure, so the sleep doc said to just stick with 8/4.
But, the problem now is with centrals. I am very sensitive to them, and have 2 issues. The first is when I am falling asleep I have a cluster of centrals. If I can get through them I enter a sleep state. If they are too severe it keeps me awake.
Once asleep I have a pretty steady breathing pattern. Around 15bpm, with an INSP time around 1.4, and an exp time on near 2.7 and tidal volume around 500.
When my respiration rate drops below the 10-12 range I have observed that my INSP time is hitting the max (2.0 initially) and my EXP time will begin to move up above 3.
The flow rate, tidal volume, etc. will become erratic, and a central or cluster of CA's are going to show up. It has been getting to where I am not sleeping through them much anymore, so that is limiting my time on the machine.
I first tried an experiment with changing the pressures to see if the "best" settings would make a difference. I used the auto settings with ps and ramp to get to sleep at the epap of 4. A setting of 10/4 gave me the best I:E ratio (ResScan stats). But it did not really help to eliminate the centrals.
I made a small change to TiMin from 0.3 to 0.6. My thought behind this was that when I took the slightest bit of inhalation to start the IPAP that it would push a little more air to where it would help me get take a breath. I can't go too long with it though because of my problems with exhaling against an ipap.
This helped a little to reduce the clusters of CA's. But it did not eliminate the breathing disruptions that lead to the ca's.
I changed the TiMax from 2.0 to 2.3 and 2.4 My thought was that it would increase the IPAP time to "force" me to breath, and hopefully would push me through a CA, or even stop the CA from happening.
This gave me the longest continuous times on the machine. For 2 nights. It increased the number of CA's, and even brought up some OA's. But I slept right through them,,, for those 2 nights.
The next 3 nights were terrible, a barrage of CA's that kept me from even getting to sleep with the machine.
I reduced the TiMax to 2.1 and I can get to sleep with it again, but once again, I am hyper sensitive to the CA's and am only getting about an hour on it before a CA or a disruption that would lead to a CA wakes me up.
In doing more researching on TiMax, I am seeing that it might be better to reduce it instead of increase it. Getting too long of an IPAP cycle could lead to an imbalance of the co2 where your body stops inhaling to let the co2 return to the level it should be at.
The 2nd and 3rd links deal with MS and COPD, but what I liked was the easy to understand explanation about co2 and ventilation.)
Later today I plan on taking a nap with the TiMax set to 1.8 to see if that makes a difference. If it does I will post back on here and you can consider whether you want to try to decrease TiMax to see if it makes a difference for you too.