This might be a long one so buckle Up...
I don't know how much you know about UARS. Most of what I know comes from this guy - from what you've said above you might get a bit of a jolt at 2:05 - I did (daytime sleepiness hit in my mid 20s, 6ft 2in, 75kg / 165lb).
https://www.youtube.com/watch?v=sa9zNYpTWlM
So UARS, by his definition, is not about complete blockages. Its about trying to breathe through a narrow opening - "breathing through a straw". A single UARS "incident" can go on for several minutes or even an hour. Your breathing will be in steady state - same one breath to the next - doesn't have to be increasing or decreasing like apnea/hypopnea - its just restricted enough to cause some light to be flashing in the brain to stop you getting into a proper sleep state.
The following is from my flow rate graphs. Top two from last night. Bottom one from early December before I discovered Oscar.
The top trace is what you want. Regular breathing. The inspiration section above the mid-line should be like half an egg (or sine wave if you prefer) with a nice curved top. The middle trace is when some kind of minor obstruction is in the way. The inspiration flow gets to some level and can't get any higher so it continues about that level for longer than normal before dropping off - "flattening of the inspiration curve". There is a whole zoo of such flow limitations (see
https://www.apneaboard.com/forums/Thread...#pid461525). The third graph is when the brain starts to panic and starts gasping / panting. Broadly each time the line goes from below to above the mid-line is counted as a breath so the higher your respiratory rate is recorded the more likely you are having issues with UARS-style flow limitations.
Note that the flow is not settling near zero in any of these situations - so no OA or H events will be recorded. Your body is getting enough oxygen so it will not show up in SpO2 traces (and it didn't in mine). But your brain may have some warning light flashing in scenarios 2 & 3 which means you wake up unrested.
Bluntly IMO CPAP machines are not designed / set up with the intention of dealing with this kind of issue. They will be regulated to focus on OSA. From my rooting around in the last few weeks the flow limitations score you see on OSCAR is heavily weighted towards OA / H like events. You can get periods of significant "not great" form which only get 0.1 flow limitation score.
Here is your respiratory rate graph from last night.
From my experience the restriction is cleared by shifting in your sleep (I video myself) but as you start to drift deeper into sleep in a new position it tends to re-emerge.
Zoom in to the detail of your Flow Rate graph at the times highlighted by the red line. Look at 60 seconds of data and fix the Y-axis so that you look at the same height each time (right click to the left of the graph on "Flow Rate" - Y-Axis -> "scaling mode" = override, min = -40, max = 40). Compare it to the Desired From & "Not Great" above.
Mr Veer has another video titled "Why Doctors Don't Understand UARS" from Nov 2023 outlining why it is so difficult to detect. There doesn't seem to be a real practical test for UARS. Sleep clinics have a process set up for OSA and will declare you treated with AHI < 5. So if, like me, you have UARS-like issues and OSA (supine positional), you'll be declared treated any time you raise ongoing daytime sleepiness and sent on your way.
As far as treatment goes, its the same as OSA. CPAP/APAP/BiLevel if it works for the individual. The word on the street here is that having a large difference between inhalation and exhalation (BiLevel) is good but try telling that to a sleep specialist. A MAD may be helpful. There is also the option of surgery. In the last couple of weeks I've found a soft foam surgical collar transformational.
Upload your flow rate detail (during the worst of the red line areas) and we'll see if they look like any of the "zoo".