AHI's On Different Machines

I'm sure this has been discussed here before but I could not find it. My question is, does Resmed count the CA's toward the total AHI's as Respironics does?
In other words my AHI's on Respironics average 4.0. (3.0 ca, +.3 oa,+ .7 h). Would a Resmed show an average AHI of 1.0 ?
I've tried every possible tweak that I can think of and continue to be amazed at the the folks that have an AHI less than 1.0. I've failed to notice what kind of machine they were on.
Thanks again to this wonderful group of friends and friends that I haven't met. Have a blessed New Year!
B.D.

I don't know if the S9 counts CAs toward the AHI or not.

What I do know is that when I was using the Respironics M Series, I got AHI consistantly below 1 but with the System One, I very seldom get below 1 with my AHI. I have the same settings as I had on the M Series.

The System One counts CAs in the AHI, as you said and the M Series did not. I am getting AHIs around 2 with the System One.

Therefore it seems to be more possible for people using the M Series to get an AHI below 1 than it is for someone using the System One with the same settings in the Respironics brand anyway.

I don't know about other brands like Resmed, Intellipap or Fisher & PayKel.

If you are beginning to feel benefit from your therapy, and your AHI is below 5, you are doing fine.

ResMed's S9 AHI is AI + HI where AI is the apnea index. All apneas---centrals, obstructives, and ones that the S9 classifies as unknown because it can't decide whether they are central or obstructive because the result of of the FOT algorithm is unclear---are included in the computation of the AI.

The long term trend difference that a particular person is likely to notice in his/her AHI between brands of CPAP/APAP machines is iikely due to a combination of (i) differences between the companies' algorithms for scoring hypopneas and apneas, (ii) continuing refinements in across different generations of machines, (iii) the person's individual quirkly responses to slight differences in how the therapy is actually delivered by the different companies' machines.

All of these are part of the reasons why you see big disclaimers that AHI data is to be used for "trending purposes only."

For me, the PR S1 seems to score a whole lot more hypopneas than the S9 ever did. (S9: HI almost always equal to 0.0, never higher than 0.3. PR S1, HI almost always between 0.5 and 1.0 and usually equal to (S1 AHI - S9 AHI). My conclusion? The S9's hypopnea scoring algorithm's cutoff for scoring a hypopnea is a bit stricter than the S1's, and in my case, very few of my breathing irregularities meet the S9 definition than the S1 definition.

iirc - the Mseries records NR's = Non-Responsive's which are included in the AHI. NR's are the early equivalent of a central.

Having recently switched from an Mseries to a PRS1 BiPap, my AHI seems to be a bit lower now. Last check was <.2AHI. With the M it was <.5AHI. While negligible, I am not yet certain what accounts for the difference. The pressure seems to be running a bit lower also.