Auto-Pap pressure

st3v3k4hn · Post by **st3v3k4hn** » Thu May 17, 2007 4:03 pm

Since the previous post asked about CPAP pressure I thought I would post some questions about Auto-Pap pressure. My range is currently 8-12 so lets use those numbers in the examples. I am using Encore Pro and a new respironics M Auto-Pap (with c-flex set to 2).

If I were to have absolutely no events (ie no apneas, no flow limits, no leaks, no snores) would the pressure stay at 8 all night long?

Similarly, if I had an event drive the pressure to say 10, would the pressure stay at 10 all night even if there were no further events? Or would (should?) the pressure fall back to 8?

In other words, will Encore Pro always show an event before pressure increases? And will pressure always decrease if Encore Pro shows NO events?

Thanks...

Steve

Wulfman · Post by **Wulfman** » Thu May 17, 2007 4:23 pm

st3v3k4hn wrote:Since the previous post asked about CPAP pressure I thought I would post some questions about Auto-Pap pressure. My range is currently 8-12 so lets use those numbers in the examples. I am using Encore Pro and a new respironics M Auto-Pap (with c-flex set to 2).

If I were to have absolutely no events (ie no apneas, no flow limits, no leaks, no snores) would the pressure stay at 8 all night long?

Similarly, if I had an event drive the pressure to say 10, would the pressure stay at 10 all night even if there were no further events? Or would (should?) the pressure fall back to 8?

In other words, will Encore Pro always show an event before pressure increases? And will pressure always decrease if Encore Pro shows NO events?

Thanks...

Steve

First one: "Yes" (theoretically)
Second one: "No" (pressure would fall back to your bottom pressure)
Third one: "Yes" ("events" drive the pressure increases)
Fourth one: "Yes" (at some point, pressure always falls back to lowest point until events occur)

Den

jskinner · Post by **jskinner** » Thu May 17, 2007 4:25 pm

st3v3k4hn wrote: If I were to have absolutely no events (ie no apneas, no flow limits, no leaks, no snores) would the pressure stay at 8 all night long?

Yes.

st3v3k4hn wrote:Similarly, if I had an event drive the pressure to say 10, would the pressure stay at 10 all night even if there were no further events? Or would (should?) the pressure fall back to 8?

It would eventually fall back to 8cm.

st3v3k4hn · Post by **st3v3k4hn** » Thu May 17, 2007 5:03 pm

Wulfman wrote:First one: "Yes" (theoretically)
Second one: "No" (pressure would fall back to your bottom pressure)
Third one: "Yes" ("events" drive the pressure increases)
Fourth one: "Yes" (at some point, pressure always falls back to lowest point until events occur)

Cool. So far, things behave as I would expect
Next question. Does the Auto-pap respond differently to different event types? For example would it react the same to a snore as it would to a leak or an apnea?
Thanks again...
Steve

Wulfman · Post by **Wulfman** » Thu May 17, 2007 7:59 pm

st3v3k4hn wrote:
Wulfman wrote:First one: "Yes" (theoretically)
Second one: "No" (pressure would fall back to your bottom pressure)
Third one: "Yes" ("events" drive the pressure increases)
Fourth one: "Yes" (at some point, pressure always falls back to lowest point until events occur)
Cool. So far, things behave as I would expect
Next question. Does the Auto-pap respond differently to different event types? For example would it react the same to a snore as it would to a leak or an apnea?
Thanks again...
Steve

There is only one "response" that the machine can do to a detected event....and that is to raise pressure. So, in that respect, I would say "No". Also, when it responds, it increments 0.5 cm at a time.....testing to see if that takes care of it before moving up another 0.5 cm. This process can take time.....especially if it's sitting at 8 and it takes a pressure of 12, 13 or more to stop an event. In the meantime, your blood may not be getting all the oxygen it should be getting (if the events are significant). So, in my opinion, if you're going to use an Auto (in auto mode), your bottom pressure should be high enough to take care of the majority of events.
At some point, if a detected event does NOT clear itself (with a Respironics machine) within a certain number of raises of pressure, it will back off (in case it's a Central apnea).

If you've got a combination of leakage, snoring, flow limitations, hypopneas, obstructive AND central apneas ALL going on.....AND, the top pressure setting is wide open......you MAY have a "runaway"......and a very bad night.

Den

st3v3k4hn · Post by **st3v3k4hn** » Fri May 18, 2007 4:44 pm

So if "events" drive the pressure increases and a lack of events means pressure should decrease, what is going on here? This was a sort of bad nite in general, but I especially dont understand the rise and consistent high pressure in the highlighted area (or after hour 8, which I forgot to highlight, sorry)...
As you can see, I am sleeping alot but not feeling that rested which is why I am asking all these questions. My average pressure is usually lower than this, as is my AHI index # (usually between 1 & 2), otherwise this is pretty typical...
Steve

Goofproof · Post by **Goofproof** » Fri May 18, 2007 5:33 pm

I would say these are caused by leaks, also you can't expect the machine to react quickly to events if it did, that alone would cause sleep destrubance. Jim

Wulfman · Post by **Wulfman** » Fri May 18, 2007 5:41 pm

Goofproof wrote:I would say these are caused by leaks, also you can't expect the machine to react quickly to events if it did, that alone would cause sleep destrubance. Jim

I agree. If you'll notice when your leak dropped in the middle of that, your pressure dropped, too. And, after "hour 8", it did something similar.
Try it on a straight pressure of 10 for a week and see what it looks like.

Den

st3v3k4hn · Post by **st3v3k4hn** » Fri May 18, 2007 9:32 pm

Goofproof wrote: ... you can't expect the machine to react quickly to events ...

This doesn't seem quick to me. Its hard to tell exactly, but it appears that nothing happens for more than a half-hour in both cases and the pressure still doesnt drop. I was expecting more like a few minutes?

Wulfman wrote:... Try it on a straight pressure of 10 for a week and see what it looks like...

OK, maybe I'm confused, but won't it just be a straight line? What could I learn by doing this?!?

Steve

Wulfman · Post by **Wulfman** » Fri May 18, 2007 9:38 pm

st3v3k4hn wrote:
Goofproof wrote: ... you can't expect the machine to react quickly to events ...
This doesn't seem quick to me. Its hard to tell exactly, but it appears that nothing happens for more than a half-hour in both cases and the pressure still doesnt drop. I was expecting more like a few minutes?

Wulfman wrote:... Try it on a straight pressure of 10 for a week and see what it looks like...
OK, maybe I'm confused, but won't it just be a straight line? What could I learn by doing this?!?

Steve

You were still leaking......the machine had to compensate with more air.

I guess you'll find out if and when you try it.....
(some straight lines can be a GOOD thing)

Den

DreamStalker · Post by **DreamStalker** » Fri May 18, 2007 9:43 pm

Yep ... looks like you need better control of the leaks.

blowfish · Post by **blowfish** » Fri May 18, 2007 10:04 pm

Snoredog · Post by **Snoredog** » Sat May 19, 2007 12:48 am

st3v3k4hn wrote:So if "events" drive the pressure increases and a lack of events means pressure should decrease, what is going on here? This was a sort of bad nite in general, but I especially dont understand the rise and consistent high pressure in the highlighted area (or after hour 8, which I forgot to highlight, sorry)...
As you can see, I am sleeping alot but not feeling that rested which is why I am asking all these questions. My average pressure is usually lower than this, as is my AHI index # (usually between 1 & 2), otherwise this is pretty typical...
Steve
<snipped>

Your leak rate is fine, where you highlighted the Pressure, doesn't mean anything other than the Auto:Max wasn't high enough so it "flat-lined". If you look at that dohickey in the center or the pressure drop, on either side of it is a peak pressure that flat-lined. If you had your Max pressure up higher there should have been a peak on each side (where you have it highlighted).

Since you are still showing some OA's you need to increase the Max pressure from current 12cm? to like 14 or 16cm. Then if you can tolerate it, bumping the Minimum pressure up from current 8cm to 10cm might results in better sleep. So your effective new range would be 10cm to 16cm. If you are not already at Cflex=3, if you bump up the Minimum pressure you can try increasing Cflex by 1 to help you tolerate the higher pressure. Before giving up on a higher Cflex try it for a 4-5 minutes if you can it can take your body a few minutes to get used to the new setting.

rested gal · Post by **rested gal** » Sat May 19, 2007 6:24 am

st3v3k4hn, I'm no expert on the way autopaps work, but I think the machine probably does a lot of behind the scenes sensing that we aren't going to see reflected in the data.

By that I mean... I believe the machine looks at subtle changes in airflow to decide what to do next. It's not just looking at the events you see tick marked, and then taking action. The marked occurrences are the events that actually happened despite the machine working to proactively prevent "events" -- apneas, hypopneas -- as well as flow limitations, snores.

So, if we see pressure rise with no "event" immediately preceding it, and the leak rate is normal (which I think yours was during the area you highlighted on the graph) my bet would be that the machine was seeing enough flow limitation from you that it decided more pressure was needed. Even if the flow limitation was not "limited enough" to warrant a tick mark on the data.

In the middle of the highlighted area, your breathing might have normalized some for awhile, so the machine did start the gradual move down. But apparently during that pressure drop in the center of the highlighted area your breathing showed signs of a problem again, so the pressure moved back up. It moved back up to PREVENT an event from happening. If the event is prevented and doesn't happen, it's not going to be marked. 'Cause...it didn't happen.

In other words, the machine was seeing problems with your breathing during the highlighted time. The problems just didn't get "worse enough" to trigger the official marking of an event. But the problems did warrant keeping the pressure up.

There was almost surely some amount of flow limitations happening in varying degrees all during the highlighted time for the machine to stay up there so long, try to come down, and then say (in effect) -- "Nah, when I try to move the pressure down, the airflow becomes more limited (restricted) again...gotta go back up BEFORE it turns into an official "flow limitation" or worse.

I could be very wrong about any/all of that. I don't know much about the way autopaps go about doing their thing.

st3v3k4hn · Post by **st3v3k4hn** » Sat May 19, 2007 12:42 pm

rested gal wrote:... I believe the machine looks at subtle changes in airflow to decide what to do next. It's not just looking at the events you see tick marked ...

Thats what I think too, and thats why I asked this question to begin with, but so far the consensus seems to be that you WILL see an event for each increase. I wish someone knew for sure...

As far as raising pressure, I don't think I need to. As I said this was a "bad" night for me. Here is a graph for a more typical night. 90% pressure is at 10 (which was also my titrated pressure) and AHI was close to 1...

Thanks again! Any and all feedback / opinions / advice appreciated!

Steve

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