APAP Anomaly in APAP Mode

ZPAP · Post by **ZPAP** » Fri Dec 01, 2006 10:22 am

I have OSA with a recent PSG titration of 9cms H2O pressure.

I've been a hosehead for 9 years, but have been using a new REMStar M Series Auto for about the past 10 days. For 5 of the days, I used the machine in APAP mode, with pressure set at 7-12 or 8-12. The other half of the time, I've set the machine to CPAP Mode at 9. At all times, I've used C-Flex (generally at 2) and the heated humidifier at 2-4.

What's surprised me is that ALL of the nights in APAP Mode have resulted in an AHI of 3-6, and ALL of the nights in CPAP mode have AHI's of less than 3. I recognize that these are small numbers, but thought that, if anything, the experience would have been reversed.

Any thoughts?

Michael

oldgearhead · Post by **oldgearhead** » Fri Dec 01, 2006 10:28 am

Is there a difference in hypopneas? If so, the higher CPAP pressure may be treating you better than APAP.

ZPAP · Post by **ZPAP** » Fri Dec 01, 2006 10:35 am

oldgearhead wrote:Is there a difference in hypopneas? If so, the higher CPAP pressure may be treating you better than APAP.

Yes, OGH. Under CPAP, only 1 or 2 hypopneas; under APAP, 6-18. But, the interesting thing is that many of the hypopneas are coming at pressures ABOVE the CPAP titrated pressure.

One would think that the opposite would be true -- why would higher pressures result in more events?

Michael

af · Post by af » Fri Dec 01, 2006 10:41 am

I have only been on apap for a few weeks, but what you are saying sort of confirms what I'm seeing in my own reports. I think it also shows that Rested Gal is right when she says that the low end of your apap range should be at or very close to you titrated pressure. Otherwise, the airway is not splinted open enough to stop hypopnias and apneas in the first place. I think thats why your AHI is higher in apap. My range is now 8-13, and my AHI is running 5 to 9, and I'm going to move the low end up slowly and see if I can get it consistently below 5.

af · Post by af » Fri Dec 01, 2006 10:44 am

Michael, I am seeing it overshoot also. Maybe the apap is not as precise as we think it is.

Goofproof · Post by **Goofproof** » Fri Dec 01, 2006 10:54 am

Also at higher pressures, you could be going into mouthbreathing. Also you may be changing your settings too often, your body doesn't have time to adjust to your machine changes. I would start by lowering your high pressure on APAP 1cm per week, to see the results. Don't go lower than your best CPAP pressure, and a few people do do better on CPAP. That's whywe use APAP's, to give up choices. Jim

Wulfman · Post by **Wulfman** » Fri Dec 01, 2006 10:56 am

Michael,

For the first 10 months I was on CPAP, I used a pressure of 10 and pretty consistently had an average of less than 1.0. In mid-March of this year, I upped it to 12 as I was seeing a few more apneas than was normal but still with an average of less than 1.0. In July, I switched my Auto to AFLE mode with a range of 10 to 15 and it consistently gave me an average of greater than 1.0. After a week, I switched back to CFLE mode and the numbers went back down.
I also discovered that I didn't sleep nearly as well in Auto mode due to the changing pressures......and I had more consistent apneas.

Best wishes,

Den

greyhound · Post by **greyhound** » Fri Dec 01, 2006 11:07 am

Like everyone else, I'm still experimenting with different apap ranges. Currently, I'm setting my apap minimum to my titrated pressure (a questionable one, since I barely slept during the second sleep study) and my maximum 4 cm. higher. Most of my time is spent at the minimum pressure and only rarely does it operate more than 2 cm above the minimum. For some unknown reason (and maybe I should retest it), my experience has been much better with the "titrated minimum" than it was when the minimum was set 1 cm. lower.

Snoredog · Post by **Snoredog** » Fri Dec 01, 2006 11:10 am

autopap is always going to have a higher AHI than cpap. A pressure of 9 will hide or mask events cleared automatically by that pressure so the machine will never see them. Is it they never appeared due to the higher pressure or is it the machine never seen them?

For example, if you had your Min. pressure set to 7.0 those events taking place at 4.0 to 6.0cm pressure would never been seen, if they were they would be scored under the 7.0cm pressure report. You can see this by setting the Min. pressure to 6.0 and then the next time setting it to 6.50cm, then all events from 6.0 to 7.0 get scored under 7.0cm reporting.

There is a trade off between the comfort offered by the lower pressure of autopap vs the worst case pressure especially if you suffer from aerophagia.

why would hypopnea increase with pressure? Could be sleep onset events or pressure induced central hypopnea if you are at risk of those.

you could optionally set your Min. pressure to 9.0cm like you were on cpap and then give it say 2cm's above that for the Max. If 9.0 is ideal and clears all events it should not move higher. But if it starts running at the Max. and you feel worse then there is a problem with central and you should then reverse things and set the Max at 9.0 (to avoid more events) and/or run in cpap mode. And that is always the argument between autopap vs cpap, with cpap you don't have to worry about it misreading and going higher than it should.

these machines are NOT perfect, they misread more central events as obstructive (if you are at risk of them) more than you think.

Guest · Post by **Guest** » Fri Dec 01, 2006 1:18 pm

If you can tolerate your titrated CPAP pressure continuously (as I easily can), CPAP is generally more effective than APAP for several reasons (no sleep disruption from changing pressures, no "missed" hypopneas and fast-onset apneas that occur because the machine couldn't raise pressure fast enough to prevent them, etc.)

If you can't tolerate your titrated CPAP pressure, have a look at APAP.

I know some folks who have no problem with their titrated pressure, except for a modest increase in flatulence. Humorously, they view this as a positive, because it provides a bit of entertainment each morning. =)

Summary: CPAP's better if you can tolerate the pressure. APAP's useful for folks who can't.

ozij · Post by **ozij** » Fri Dec 01, 2006 2:50 pm

-SWS once wrote that some people react with hypopneas to pressure changes. I don't remember if he gave a link to the source, but I trust anything he writes.

O.

Guest · Post by **Guest** » Fri Dec 01, 2006 3:48 pm

ozij wrote:-SWS once wrote that some people react with hypopneas to pressure changes. I don't remember if he gave a link to the source, but I trust anything he writes.

Actually, come to think of it, this makes much sense to me... because I've noticed that:

1. when I'm breathing normally with CPAP and then I take my mask off (reducing the pressure), it's harder to breathe for the first breath or two, without the pressure being present. If this pressure drop was caused by an APAP machine rather than a mask removal, I can see how an apnea or hypopnea or some other form of event (delayed breaths?) could result.

...and in the reverse direction:

2. When my CPAP is running already and I put the mask on, often my inhale reflex doesn't work for a few seconds... meaning the pressure increase causes me not to automatically take the first breath, or two. I have to consciously inhale. Again, if this pressure increase was caused by an APAP machine rather than by putting on a "running" mask, I can see how an event could result.

Interesting... I'm liking constant pressure more and more, the more I read and think about this... I'm just glad I can tolerate it easily.

Goofproof · Post by **Goofproof** » Fri Dec 01, 2006 4:21 pm

Anonymous wrote:
ozij wrote:-SWS once wrote that some people react with hypopneas to pressure changes. I don't remember if he gave a link to the source, but I trust anything he writes.
Actually, come to think of it, this makes much sense to me... because I've noticed that:

1. when I'm breathing normally with CPAP and then I take my mask off (reducing the pressure), it's harder to breathe for the first breath or two, without the pressure being present. If this pressure drop was caused by an APAP machine rather than a mask removal, I can see how an apnea or hypopnea or some other form of event (delayed breaths?) could result.

...and in the reverse direction:

2. When my CPAP is running already and I put the mask on, often my inhale reflex doesn't work for a few seconds... meaning the pressure increase causes me not to automatically take the first breath, or two. I have to consciously inhale. Again, if this pressure increase was caused by an APAP machine rather than by putting on a "running" mask, I can see how an event could result.

Interesting... I'm liking constant pressure more and more, the more I read and think about this... I'm just glad I can tolerate it easily.

Guest · Post by **Guest** » Fri Dec 01, 2006 4:34 pm

What's wrong about your idea. When you remove the mask or put it on, you are making a huge change in pressure. When the machine changes pressure it in small steps (1 cm).

Perhaps, but still, the difference is only in the magnitude, not in the essential nature of what's happening in both cases. However, I do admit that the great difference in magnitude might make the difference between events and no events, sure.

Just an interesting observation that I thought might tie in.

-SWS · Post by **-SWS** » Fri Dec 01, 2006 10:13 pm

ozij wrote: I don't remember if he gave a link to the source, but I trust anything he writes.

Whew! That's by far the scariest thing I've ever read on any message board, O.

Anonymous wrote:
What's wrong about your idea. When you remove the mask or put it on, you are making a huge change in pressure. When the machine changes pressure it in small steps (1 cm).

Perhaps, but still, the difference is only in the magnitude, not in the essential nature of what's happening in both cases. However, I do admit that the great difference in magnitude might make the difference between events and no events, sure.

Just an interesting observation that I thought might tie in.

I think Jim's comment is right on the money, and your own follow-up analysis is correct as well, guest. The magnitude of both the pressure drop and the physiologic response are extreme when you suddenly remove your mask. As Jim points out, the APAP very gradually administers slight pressure increases to avoid triggering that same physiologic response that you observed.

You are more comfortable with fixed pressure than varying pressure, Guest. That's pretty much what I originally expected as my own response to PAP therapy as well. My fixed pressure is only 10 cm. To my initial surprise, however, I ended up sleeping more comfortably with APAP than CPAP. My best guess is that APAP's lower mean pressure just may source fewer sensory-based cortical arousals as I sleep. And it really doesn't take much sensory input to deteriorate my sleep.