High AI and constant pressure (using autoset)

[derek70]

I'm intrigued why some nights mi AI > 1 using Autoset and the pressure keep at minimum?
I've been used to Ai=0.1 and I see Autoset working at my graph and then last night my AI=0.9 with no pressure change !!

Have some of you experienced this with S8 Autoset II ??

[derek70]

Same last night.
5 apneas events (AHI of 4) e minimum pressure.
Some of you have experienced this?

[MaxDarkside]

5 apneas events (AHI of 4) e minimum pressure.

Not sure I understand. To have 5 events and an AHI of 4, you had to have slept just a bit more than an hour. Perhaps a typo? On the other hand, an AHI of 0.1 is like nirvana for many of us. Having an AI=0.9 with no pressure change is probably not abnormal. The events may not have been of a nature for the machine to decide to raise pressure, but I'm unfamiliar with the S8 nor the situation (the nature of the events, how they are spaced, their length, etc.). "Central" (open airway) events don't cause a pressure change, for example, and can be caused just by rolling over, moving.

I myself am not too concerned unless my AHI heads over 5, since less than 5 is considered "normal" for everyday folks without sleep apnea and considering in my sleep study I had an AHI in the 40's.

[jweeks]

Derek,

Can you post a graph of your data from the machine? When you say that the pressure doesn't change, can you tell me what pressure it was stuck at? I can think of two possible reasons that pressure wouldn't change...(1) you were already at the max pressure, or (2) you had a high mask leak and the machine couldn't adjust. I don't suspect either of these issues in this case, however, because of your low AHI. There is a 3rd reason that an APAP wouldn't adjust for an event, but that is RERA events, which APAP doesn't effectively treat. In fact, a 4th reason comes to mind...a bad air flow sensor. At any rate, I am really curious, and I would enjoy seeing your data dump.

-john-

[derek70]

Thanks max and jweeks. I'll post a detailed graph later.

In fact I had AHI=4.5 and AI=0.9 maybe 6 hours of sleep for this particular night of sleep.
The pressure was stuck at the minimum 11.6.

My average is AHI=3 with Autoset working to 12 or even 13

S8 has very limited data information, no airflow graph, no central report, no rera...

[Guest]

Thanks max and jweeks. I'll post a detailed graph later.

In fact I had AHI=4.5 and AI=0.9 maybe 6 hours of sleep for this particular night of sleep.
The pressure was stuck at the minimum 11.6.

My average is AHI=3 with Autoset working to 12 or even 13

S8 has very limited data information, no airflow graph, no central report, no rera...

Do you realize that the S8 algorithm (called the "A10" for obvious reasons) will not pursue apneas above the pressure of 10 cm. unless preceded by snoring or flow limitations? (it is supposed to prevent pressure-induced Central Apneas)
So, if you are not having those preceding events, using the S8 in a range of pressures is going to allow events (that needed higher pressure to eliminate) to occur and you will have higher AHI numbers. Many people were better off using the S8 APAPs in CPAP mode.

It's also typical of the S8 machines to over-count hypopneas which also creates a higher AHI.

These scenarios and characteristics have been discussed at great length on these forum pages in the past.

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