[CPAP] Increases in pressure and Clear Airway events

[bzz08]

I'm new here but have been using my CPAP for almost three years. I only recently discovered OSCAR and am trying to figure things out with the Beginner's Guide wiki (extremely thorough—thanks!). I have an appointment tomorrow morning with my sleep doctor but perhaps I can get some light shed on things here.

In January I had my pressure lowered from APAP range 4-9 to a constant 6 after a new sleep study (which I didn't think was accurate). The 6 surprised me because the pressures had been reading in the high 8s for quite some time. Of course, the constant 6 did not work and I had to have it changed back to APAP, first to a range of 6-8 (February), and a bit later to 6-10 (March).

Here's what I don't get: I thought that on APAP I would see the pressure fluctuate from day to day—some days higher, some lower. But since changing back to a range of 6-8, the pressure kept inching upward only, increasing by 0.1 every night or two. That's why the range was increased up to 10. The pressure just kept going until it reached 9.9 (recently it has dropped to 9.8). Does this seem normal? Why would it keep inching up like that? If I get the range increased again, can I expect it to just keep climbing?

And now I've been noticing the same steady increase in Clear Airway events. I had never paid attention to those, which appear on the CPAP screen as "Central AI," until a few weeks ago when the number changed from 0.8 to 0.9. Again, nearly every night it creeps up by 0.1 until last night it's at 2.3. What does this mean? Have I developed Central Apnea?  

Thanks for any insight you can share.

[Melman]

Welcome. Let us help you understand your data by posting a couple of OSCAR daily charts. The instructions for how to post and how to organize your charts are found in the links below. It's important that you minimize the calendar, delete the pie chart, and organize the charts per the instructions. If you have copy of your sleep study please post it with personal information redacted. If you don't have a copy please tell us what your AHI was and what types of events were predominant (e.g.. obstructive, central, and hypopnea).

[bzz08]

I don't have a copy of either sleep study but the original AHI (2016) was 12.

This is my info for last night. It's the first night that I tried taping my mouth to address leak issues and I expected the first half of the night to look better than it does as I woke feeling that I had slept pretty well to that point. The AHI of 2.58 looks good to me, though.

[bzz08]

[attachment=13609][attachment=13610]Updated for Sunday July 14, plus the statistics screen

[Gideon]

I would like you to lower your max pressure, start with 9. I understand that you are feeling pretty good and I don't want to stop that. The idea is that by lowering your max pressure to reduce the Central component of your AHI and continue as long as your good sleep is not impacted and your overall AHI is not increasing. That part is tricky because Centrals can vary a lot from day to day for no apparent reason.

[bzz08]

So my sleep doctor would like me to have a new sleep study/titration, which I didn't expect to hear. He wants them to start the pressure at 9 and thinks that I might be better off going back to CPAP instead of APAP. He seemed to indicate that my increased centrals were related to the pressure, so I don't understand why he thinks being at 10 would be good.

I asked about the steady increase, +0.1 almost every night. He explained that it has to do with the machine figuring out what I need "based on a curve." I heard the same explanation for why my pressure acted the same way earlier this year, steadily increasing in 0.1 increments, but I still don't understand it. I think he means that if my range starts at 6 and the pressure I need is actually 9, instead of going directly to 9 it made those incremental adjustments (which would take at least 30 consecutive nights to get there)—but that still doesn't make sense to me because I thought the machine is supposed to give me what I need, at least when in APAP mode, and within the specified range.

[bzz08]

I would like you to lower your max pressure, start with 9.  I understand that you are feeling pretty good and I don't want to stop that.  The idea is that by lowering your max pressure to reduce the Central component of your AHI and continue as long as your good sleep is not impacted and your overall AHI is not increasing.  That part is tricky because Centrals can vary a lot from day to day for no apparent reason.

I will try that tonight. Maybe I can avoid having another sleep study!

[PaulaO2]

Pressure increase induced central events are common.

What may be happening is you are making changes too quickly and your brain is having problems keeping up.

Ignore the doc, he's insane.

A regular CPAP works by inserting X pressure constantly. It does not change. If your body needs more, it doesn't get it. If your body needs less, it doesn't drop. For some, that is fine. For others, it doesn't work.

An APAP works by being set a range of pressure. It starts out with the lowest then increases or stays there depends on what it detects. It detects events by reading the "echoes" of the pressure it is sending. It knows when you breathe in (no resistance) and when you breath out (air being pushed back against it). It knows when your airway is closing (more resistance being felt), when it is closed (lots of resistance), or, in the case of central events, it can tell when the air is going in but not coming back out.

When it detects these responses, it adjusts the pressure as necessary. It senses your airway is closing and increases the pressure slightly. Did the increase cause the airway to open? No? It increases again. Once the airway is open again, it then begins decreasing. If the airway remains open, it will continue to drop. If the airway starts to close again, it will maintain that lower pressure until it determines the airway is stable.

Your doctor is insane because he misunderstands how this works. And he's a sleep doc and should know better. There's no need for another sleep study. He must be getting a kickback or something for each patient he sends to get it done.

For some people, this increase in pressure can cause central events. Central events are when your brain says "The blood chemistry is fine, there's no need to breathe to filter it." There's no snoring, no struggle to wake you, because your brain says all is well. Meanwhile, the blood chemistry is NOT fine and stuff begins to happen. Eventually, the brain kicks in the breath again. For some people, the brain gets really confused. There's air coming in that it didn't expect. There's a resistance to breathing out that wasn't there before. So it stops the breathing in an attempt to figure out what is going on. This is pressure induced central events. Many of us have them. The idea is to decrease the max pressure (if APAP) or decrease the pressure (if CPAP) and wait for about a month or so then slowly increase again. Doing it in steps gives the brain time to figure out this new normal. For some people, the variable pressure from APAP is enough to confuse the brain. Decreasing the maximum helps with that. It does not mean the person needs to switch to CPAP.

If we make changes too quickly, then the body and brain can't keep up. And we don't know if the change is the cause or the result of whatever happens. We make a small change, wait at least ten days, evaluate the data, then either stick with it or introduce another pressure change. We cannot look at the data from a single night and say "my pressure is too high". We have to look at trends, such as the data from a week or more.

I had horrible pressure induced central events. When I first started, my sleep doc made changes (based on nothing other than his god-like ability) at 3mos and at 6mos. We used no data to back up his concept. But once I got a data capable machine, I could see central events were still happening. An APAP really helped me with this problem. I made slow, informed, data-backed increments until my apnea was being treated and central events were under control.

I agree that you should lower the max to 9 and wait a while. Gather data and see what is going on. If the centrals decrease, then increase to 9.5 and wait some more.

[jaswilliams]

So my sleep doctor would like me to have a new sleep study/titration, which I didn't expect to hear. He wants them to start the pressure at 9 and thinks that I might be better off going back to CPAP instead of APAP. He seemed to indicate that my increased centrals were related to the pressure, so I don't understand why he thinks being at 10 would be good.

I asked about the steady increase, +0.1 almost every night. He explained that it has to do with the machine figuring out what I need "based on a curve." I heard the same explanation for why my pressure acted the same way earlier this year, steadily increasing in 0.1 increments, but I still don't understand it. I think he means that if my range starts at 6 and the pressure I need is actually 9, instead of going directly to 9 it made those incremental adjustments (which would take at least 30 consecutive nights to get there)—but that still doesn't make sense to me because I thought the machine is supposed to give me what I need, at least when in APAP mode, and within the specified range.

The 30 consecutive nights thing is with a dreamstation when running optistart or something not a Resmed as shown by your profile. You can set cpap mode on your existing machine and try it seems like your Dr wants a new boat or something and needs the funds of an overnight study, unless your overnight study would be a bilevel titration.

[bzz08]

PaulaO2An APAP works by being set a range of pressure. It starts out with the lowest then increases or stays there depends on what it detects. It detects events by reading the "echoes" of the pressure it is sending. It knows when you breathe in (no resistance) and when you breath out (air being pushed back against it). It knows when your airway is closing (more resistance being felt), when it is closed (lots of resistance), or, in the case of central events, it can tell when the air is going in but not coming back out.

That makes sense to me. 
Now that I've been studying my data, I need to correct my description of what's happening. The steady increases that I was talking about only show up in the daily report on the CPAP screen. This is for last night, for example, and the pressure reading is just starting to come back down. [attachment=13691] 

When I look at my stats, I see that when the pressure was changed from CPAP 6 to APAP 6-8, from the very first night it did give me the full 8 for most of the night, and it continued until the range was bumped up again to 6-10. With that change the same thing happened: I immediately got the full 10. So it's not that the machine was slowly increasing my pressure, but rather that the little summary report for some reason says otherwise.

I lowered the range to 6-9 on Monday and that daily report still shows my pressure as 9.8, now starting to come down to 9.7—but the OSCAR data shows otherwise, that I'm using the upper limit of 9. That still doesn't explain to me why my Centrals have been doing the same incremental increases, though. Maybe it'll dawn on me soon.