Why AHI 2.40 not so good for one night

[CPAPforever]

My daily AHI always below 5 and usually below 2 but having extreme daytime sleepiness for a while now. This week has been quite variable and I've been looking at my data in SleepyHead. I have a ResMed S9 VPAP S. I seem to have clusters of events over 2 hour period and then uneventful remaining hours of sleep. (Perhaps this is during REM sleep or sleeping on my back but have no way to know.) Looking over 1.5 years, Sleepyhead said my best setting was 20/16.

Earlier in the week I had my first perfect night of AHI 0.0 at 19/15 which is the setting I have been using for past two months.

AHI 0.0.PNG (127.16 KiB) Viewed 1440 times

A later night this week my AHI was 3.74 at setting 19/15. After looking at the cluster of OAs and the length of time I was above AHI 5, I bumped up my setting to 21/17 (original prescription setting).

AHI 3.74.PNG (147.24 KiB) Viewed 1440 times

Last night after struggling to fall asleep at 21/17 for a more than an hour, I changed the setting down to 20/16. My AHI was 2.40 but look at the data. My AHI was above 5 and went as high as 19 lasting over two hours (25% of sleep time) with large cluster of OAs, several over 20 seconds long. The remaining hours of sleep had only a couple of events.

AHI 2.40.PNG (146.62 KiB) Viewed 1440 times

Might this indicate that I would do better on an Auto BiPAP which could adjust for this wide variability over various settings?

My pulse oximeter is arriving today. So I will looking at what my P02 is over the next month before I see new sleep doctor. (The sleep doctor I have been seeing annually since 2012 dropped all Medicare patients.)

[Pugsy]

Might this indicate that I would do better on an Auto BiPAP which could adjust for this wide variability over various settings?

Classic textbook reason for auto adjusting pressures IMHO.

Something is or has changed to cause a need for higher pressures only at that time.
The usual suspects are either supine sleeping or REM stage sleep or maybe a combination of both.

You have 2 choices right now...use higher pressures all night to prevent the whatever is causing the airway collapse to need more more or use lower pressures and accept it that you will sometimes see these ugly clusters....or get a machine that will let you use lower pressures for the bulk of the night and only auto adjust upward when needed.

[CPAPforever]

Saw new sleep doc. He said my "numbers" look great (AHI below 2). I showed him my graphs and how some nights I have ugly cluster of OAs in the middle of my sleep time and the rest of the night is perfect without any events. He agreed that this indicated that my settings were taking care of 75% of my sleep time but was obviously not high enough during the times I have cluster of OAs to prevent them. My ResMed VPAP S has almost 18,000 use hours (6 years old) so needed a new machine anyway. Just wanted to get the best machine for my issues. I got Rx specifically for Aircurve 10 VAuto from my new sleep doc. Hopefully will be able to pick up at DME's tomorrow. I have never used any auto machines so will be interested to see if those ugly OA clusters disappear and what my optimal settings turn out to be.

[Pugsy]

Should be fairly simple to come up with optimal settings in auto mode.

Mimic the VPAP S settings except set Max IPAP to 20...see what happens ...if it hits 20 during IPAP very much then increase IPAP max a little more.

[CPAPforever]

Doc said to start Max IPAP at 23 and Min EPAP at 15 because I have those ugly clusters with IPAP at 21 on fixed Bilevel. I can reduce Max IPAP when I see my data. I may never get down to Min EPAP 15 but can raise it a bit when I see my data to reduce the wide range. Will be a new adventure for me in my 20 years of OSA treatment.

[palerider]

Doc said to start Max IPAP at 23 and Min IPAP at 15 because I have those ugly clusters with IPAP at 21 on fixed Bilevel. I can reduce Max IPAP when I see my data. I may never get down to Min IPAP 15 but can raise it a bit when I see my data to reduce the wide range. Will be a new adventure for me in my 20 years of OSA treatment.

What are your settings on your VPAP S?

[CPAPforever]

The settings on VPAP S have been 21/17 or 20/16 for past 5 years. Did go down to 19/15 for a couple months.

[Pugsy]

Didn't know you were already using over 20 IPAP.
I would set it to IPAP Max of 25 and let the machine do its thing. It won't go anywhere it doesn't have a reason to go to and the difference between 23 and 25 doesn't amount to much anyway.

[palerider]

The settings on VPAP S have been 21/17 or 20/16 for past 5 years. Did go down to 19/15 for a couple months.

I'd try mimicking your settings, so, minepap 16, PS 4, maxipap 25... See what happens, post a chart tomorrow.

[D.H.]

Remember that 2.40 means an event every 25 minutes (on average). Even though they say under 5 is OK, it's far from optimal.

[CPAPforever]

My point is that averaging over 8 hours can give you a low AHI but actually hide important facts. Like AHI at 19 for 2 hours and zero events 3 hours before and 3 hours after. So 25% of my sleep is crap at AHI 19 and 75% is perfect. That is very different from events spread out throughout the night. Get the same AHI but significantly different in sleep quality.

[palerider]

My point is that averaging over 8 hours can give you a low AHI but actually hide important facts.

That's why I don't pay much attention to the AHI... I want to see the chart.

[Marillion]

With clusters of OA like that, it could be possible that there is some chin tucking going on that is increasing those numbers. A soft properly fitted cervical collar (slightly looser than required for neck injury purposes) might help prevent the OA clusters from re-appearing if it continues to be an issue. You can pick one up at Walmart or any other discount retailer. Amazon also has them. I would also recommend NOT using a very high lofted pillow.

[CPAPforever]

DME finally got all the documentaion needed from my doctor and then I had to schedule appointment with DME. I called twice to be certain they had the machine I was prescribed (ResMed Aircurve 10 Vauto) and was assured they "carry all the machines." At my appointment, they had a Airsense 10 Autoset ready and waiting. WRONG MACHINE. When tech finally read my doctor's prescription that specifically said ResMed Aircurve VAuto, NO THEY DON'T stock those. But they could give me a DreamMachine Auto Bilevel which was "just the same." NO, not the same I told him.
1. The DreamMachine has smaller water chamber for humidifier 325ml vs 380ml for ResMed. My S9 VPAP S runs dry at 6 hours because my high pressure settings. 325ml will be dry sooner.
2. The ResMed algorithm is more responsive than DreamMachine when events are sensed. DreamMachine will let me continue having OAs for longer time before bumping up pressure.

Those are the important differences but there are more. So tech says, he didn't know there were any differences but "it will take 1-2 weeks to get the Resmed Aircurve 10 VAuto". Fine, I will wait. I can't get another machine for 5 years so I want the exact machine my doctor ordered and nothing else.

Such a bummer. I thought I was getting my new Vauto Friday, but no, DME required an appointment. Made the appointment and went today and they had totally wrong machine setup ready to go (Airsense 10 autoset). Then they read the prescription and say they have to special order. I called twice on two separate days before the appointment to be sure they had the right one. The two persons I talked to didn't listen carefully and just assumed a Airsense 10 autoset).

[CPAPforever]

I have a very short neck so can't find any collar that is short enough and won't also force my mouth shut. I am an obligatory mouth breather due to small nasal passages, deviated septum. Congestion at night means if my mouth forced shut, I will wake up suffocating, unable to breathe. So have always used FF mask.

I use the new Enduro CPAP pillow for side sleeping. It works very well without knocking my FF mask around (I sleep 75% of the time on right side in sleep study). I usually wake up almost immediately when I turn onto my back because immediate obstruction. I push the pillow aside and go back to sleep without any pillow when on my back but obviously am still having OAs on my back. Add REM sleep and OAs get worse.

I have tried many things over the years with minimal success. I used a pregnancy pillow for a few years which keeps PG woman on side (better for baby). But turning over to other side or even on back a major wakeup to rearrange things.