ASV: PS Settings - Examples

[Unkikonki]

Hi there,

I've been on a ResMed AirCurve 10 ASV for almost a month now, and although therapy has improved slightly over CPAP (which was causing Complex Sleep Apnea), it is still far from good.

I would like to understand Pressure Support (PS) better, particularly PS Min.

In my machine, PS is set as a Min and Max range. Minimum can be as low as 0.00 ( = EPAP Min + 0), and Maximum as great as 17.00 ( = EPAP Max + 17.00).

If I understand correctly, PS's function is to deliver enough inspiratory pressure to assist with respiratory drive, particularly to prevent Central Apneas. Now, my question is, how do you determine ideal PS Min and PS Max? I know the easy answer is "a titration study", but could you give examples of what characteristics of an individual would determine those settings? Does it depend on the person's physiology, respiratory mechanism, sleeping position, a combination of these? Could you give concrete examples of an individual who might prefer low PS Min and of another one who would benefit from a higher PS Min?

I guess the reason I am asking this is because, in my mind, the ideal settings would be the least "invasive" ones were the machine provides just enough assistance to prevent apneas without interfering too much with the person's natural respiratory mechanism. Thus I assumed that the lower the pressure and the narrower the range EPAP and PS were set to, the better. But I'm starting to think this assumption might be wrong. Maybe ASV does work best with a wider range (something I actually tried the first nights with awful results).

[Sleeprider]

Well, the PS min has very little to do with respiratory drive, and is more related to comfort and flow limitations at the minimum. Why not just post a chart that shows results and settings? We do know how an ASV works.

[Unkikonki]

Hi Sleeprider. I didn't want to make this thread about me specifically (there's already another thread about my treatment in which you and SarcasticDave have been very helpful) but to discuss PS in more general terms.

You mentioned comfort and flow limitations. Is that a trade-off? The lower the PS Min, the greater the comfort but the higher the risk of flow limitations, and vice versa?

[Sleeprider]

With ASV, I use EPAP min to provide comfort, which is analogous to flow limitations, RERA and hypopnea. For some reason, very low PSmin does not seem to work well with ASV, and I want to see at least 2-cm. Higher PS-min can cause hypocapnea, that individuals with central apnea don't tolerate well. With that said, it depends on the individual and the reasons they are using ASV, so there are no set rules. We used to see ASV used by individuals with central and complex apnea, so for them, a 2-3 cm PS min seemed to work pretty well. Recently we have seen more individuals with "self-diagnosed" UARS using ASV, and higher PS min might be appropriate for them. It really depends on the individual's reasons for using ASV and how they respond. I wish I could say 3-cm PS -min works for everyone, but it's just not that easy.