AHI and Auto CPAP (APAP)

I have switched to a System 1 Auto machine the 550 model. I originally was prescribed a pressure of 7cm and since using the auto mode I have set ti to range from 7 - 12.

I get a good night's sleep but I have noticed that my AHI is under 5 (like 2.6-4) on a pressure of 7cm but when the machine is at higher pressure it gives me an AHI of 6 -8.

I am assuming that if I was only at a pressure of 7 then at that point in the night i would expereince much more apnea and that the AHI at 7 would be higher.

Is it that my AHI climbs at these pressures because the machine senses apnea/obstruction and then generates more pressure to compensate?

Should I go back to just CPAP mode?

Do you have the Encore Viewer software for the PR System One machine you're using?

Some people do indeed do better on straight CPAP for a variety of reasons. One of those is that some people begin to get pressure-induced central apneas as the pressure is increased once the pressure gets above 10cm. It could be that you are unusually sensitive to pressure and that you are beginning to experience centrals at pressures that are in your APAP range that are also above your titrated 7cm (hence you had really good AHI's when you were using straight CPAP at 7cm). The only way you could tell for sure would be to download your data and see what's happening in Encore.

But since your AHI went up in APAP mode and you had good results with straight CPAP at 7cm, I'd say go back to straight CPAP at 7cm if you were comfortable sleeping with that setting.

I really wanted to like APAP. The whole theory made sense to me. But, alas, I can't tolerate it and do way better on straight CPAP.

I, too, get much better results with CPAP.

However, make sure your leaks are still minimal at the higher pressures. That will almost certainly affect AHI.

Very good advice, robysue. You touched on all the things I was going to say.

Great personal experiences, Lee Lee, Jersey Girl, and LinkC.

If you do not have access to the data (Encore Viewer), and you really WANT to use apap mode, you could try tightening your range, so 7-9 ir 7-10 and see how you do. But, there is nothing wrong with going with straight cpap, if that works for you!

happy sleeping!

I guess, I'm one of the different types. I have been on straight cpap since 1977 and last month went on apap and my AHI has been averaging 3.1. I really like the difference in the breathing and lack of adjusting my mask several times a night because I think there is a leak. My arousal rate is down and which means I don't wake up five or six times a nite to go to the bathroom. YMMV, but I am really pleased with apap.

I have encore pro so will look at the graphs rather than just the AHI on the summary page.

Silly question...AHI take into account both central and obstructive episodes correct?

What I do find with a pap is that I wake up less through the night. Another option is to go on cpap for a couple of days and compare data with the period on apap.

I will report back soon!

Thanks for the insight.

alex a wrote:Silly question...AHI take into account both central and obstructive episodes correct?

Yes, AHI takes into account central (clear airway) apneas, obstructive apneas, and hypopneas.

and NO questions are silly! Just keep asking.

and if you need help with those graphs, you can just post them here, and many forum members will help you.