Question about rising pressure on APAP?

[Mtnman]

Hi all!

I'm on week two and have been slowly adjusting my low end pressure up. I've worked from 4 to 9.5 where I am now. I've noticed that my average pressure per night has risen from 9 to 12, in relation to my raising my low end pressure.

This doesn't make sense to me. It seems like my APAP should find my needed pressure without regard to my "low" setting. The needed pressure would stay the same regardless of the "low" setting, right?

Let me know what you think and thanks...

[Snoredog]

[quote="Mtnman"]Hi all!

I'm on week two and have been slowly adjusting my low end pressure up. I've worked from 4 to 9.5 where I am now. I've noticed that my average pressure per night has risen from 9 to 12, in relation to my raising my low end pressure.

This doesn't make sense to me. It seems like my APAP should find my needed pressure without regard to my "low" setting. The needed pressure would stay the same regardless of the "low" setting, right?

Let me know what you think and thanks...

[Sleepdeprived]

[quote="Snoredog"][quote="Mtnman"]Hi all!

I'm on week two and have been slowly adjusting my low end pressure up. I've worked from 4 to 9.5 where I am now. I've noticed that my average pressure per night has risen from 9 to 12, in relation to my raising my low end pressure.

This doesn't make sense to me. It seems like my APAP should find my needed pressure without regard to my "low" setting. The needed pressure would stay the same regardless of the "low" setting, right?

Let me know what you think and thanks...

[Guest]

That was a very helpful answer. I have not been titrated so I'm figuring this out on my own. My AHI, by the way, is now at 1.9 which I guess is really good. I kept raising my pressure because I just felt like I was still having to "pull" the air in, where as at pressure 9.5, I feel like the airflow is "right there" the moment I start to inhale. Your comments about Centrals is extreamly interesting and I'll difinately take this into consideration.

Thanks again!

BTW, I think I'm starting to feel the positive effects of CPAP. More energetic upon waking and not so tired at the end of the day. I'm pretty pumped that this may be working!

[rested gal]

it has to see 3 consecutive events in a row before it logs them as NRAH and drops pressure.

As I understand it, the Respironics autopaps are not looking for "3 consecutive events in a row" as possible "NR" events. I think it logs an event as an NR (Non Responsive...doesn't respond to additional pressure) when 3 consecutive slight increases of pressure produce no improvement in the airflow. Then, as you said, it backs off the pressure in case that was a central apnea.

Look for examples of James Skinner's "Apnea vs. Pressure" report, it will show a curve, it will also show as you increase pressure you can increase the frequency of events seen. When that happens you are over titrated.

I always wonder about "the chicken and the egg." I'd think there could be several scenarios that would produce a picture of more events (apneas/hypopneas) at higher pressures. I'd think it could be possible for the machine to be using higher pressures because they are needed. The events might be coming first instead of being produced by the pressure.

And, of course, I always suspect GERD when events keep happening in clusters despite rather high pressures.

[roster]

........

And, of course, I always suspect GERD when events keep happening in clusters despite rather high pressures.

Do you mind elaborating on that? I was diagnosed in June with asymptomatic gerd.

[rested gal]

Actually, I've picked up what little I know about how GERD can cause problems with getting effective cpap treatment, and how it can mess up what an autopap is "seeing" for some people, from another poster... -SWS

I think of the problem this way. CPAP treatment is designed to push aside soft tissue. But when the back of the throat is getting nightly acid baths, the tissue can become irritated, swollen and hard. Vocal cords bathed in acid can spasm. It can be difficult for cpap air to push aside swollen tissue. Like hitting a brick wall.

I could be wrong about this, but I think acid irritated, swollen tissue on some nights (or at some times during any night) could result in the prescribed pressure not being "enough" with a straight cpap machine. And it could cause an autopap to keep raising the pressure almost to no avail.

Loonlvr's saga is what I have in mind. -SWS is the one who zeroed in on what the problem might be. I just passed the word along.
Nov 05, 2005 subject: SUCCESS AT LAST-GERD,420E, PRILOSEC AND BENADRYL
viewtopic.php?t=5551

It wasn't really a matter of switching to a different autopap. It was a matter of stopping the irritation and swelling of the tissue inside the throat and/or vocal cord spasms.

Another smart poster from long ago -- Mikesus -- had also brought up the acid reflux possibility back when the first thread about Loonlvr's massive clusters of OA's, NR's and skyrocketing pressure-being-used were first discussed. Links to the first discussions about Loonlvr's terrible clusters of apneas were in the "Success At Last" thread.

And below are some links about sleep apnea and GERD often going together. "Silent Gerd" is especially insidious, as the sufferer will not have the usual symptoms of "heartburn" and not know they even have it. As with sleep apnea, if it happens only at night when the person has been lying down for awhile asleep, the person may never feel any symptoms at all.

Apparently the heaving struggle of the diaphragm and abdomen trying to breathe in past an obstructive apnea is likely to shove acid upward from the stomach. I guess that could become a vicious cycle creating an even more restricted airway as the tissue becomes irritated and swollen inside the throat.

http://www.sciencedaily.com/releases/20 ... 080008.htm
"All patients with sleep apnea should be evaluated for gastroesophageal reflux," said J. Barry O'Connor, M.D., of Duke University Medical Center, one of the investigators.

http://www.medscape.com/viewarticle/516189

http://www.entnet.org/healthinfo/topics/GERD.cfm

http://www.grandtimes.com/GERD.html

[Guest]

Hi all!

I'm on week two and have been slowly adjusting my low end pressure up. I've worked from 4 to 9.5 where I am now. I've noticed that my average pressure per night has risen from 9 to 12, in relation to my raising my low end pressure.

This doesn't make sense to me. It seems like my APAP should find my needed pressure without regard to my "low" setting. The needed pressure would stay the same regardless of the "low" setting, right?

Let me know what you think and thanks...

Actually, it makes sense to me.....and from a slightly different viewpoint than the others.
Assuming that Centrals and GERD are NOT a factor (they're a reality, but much less common than Obstructive), and "all other things being equal", it's possible/probable that you haven't reached a high enough bottom pressure. If your machine is set too low and it takes a higher pressure to clear an event, your event may be over before it can reach the pressure needed to stop or PREVENT it, but MAY reach a pressure that can stop part or all of it. Sometime after that, the pressure drops back down and the cycle starts over again

Your APAP will help find your needed pressure IF it's properly configured.....which means a narrower set of pressure settings.
It also depends on what your reports are showing. Are snores driving up the pressure? It sounds like your AHI is pretty decent. Your "average" pressure is usually below what your ideal pressure needs to be. AND, depending on what your reports show (types of events), your 90% pressure may be higher than what you would need if you were using single pressure, too.

I would say to keep narrowing your pressure range (moving your bottom pressure up) and watch your reports.

Best wishes,

Den

[ozij]

Hi all!

I'm on week two and have been slowly adjusting my low end pressure up. I've worked from 4 to 9.5 where I am now. I've noticed that my average pressure per night has risen from 9 to 12, in relation to my raising my low end pressure.

This doesn't make sense to me. It seems like my APAP should find my needed pressure without regard to my "low" setting. The needed pressure would stay the same regardless of the "low" setting, right?

Let me know what you think and thanks...

Another viewpoint comes from the mathematical facts of life:

Suppose you sleep 8 hours and that as a rule, it takes a pressure of 6 to keep your airway open half of the time. Let's say you spend 4 hours of your time a 6, 2 hours at 7, and an hour each at 9 and at 10.

Calculating the average perssure would mean adding hours times pressure, and dividing by the total time. In this case, we'ld have:
4*6 + 2*7 + 1*9 +1*10 = 57
Divide that by 8    ( 57/8 ) and your average pressure is 7.125.

Now you narrow the range - the bottom is 7, nothing else changes.
Instead of a total of 57, the total is higher, and automatically, so is the averag:
4*7 + 2*7 + 1*9 + 1+10 = 61

Divide 61 (total pressure) by 8, and now your average pressure is 7.625.

In both cases, your 90% pressure - the pressure at which or beneath which you spend 90 percent of the time is 10.
The precentile is not affected by the ends of the range, an average is - simply because of how it's calculated. And that is exactly why "needed pressure" is always defined as the xx% pressure, and never as the average. The average depends on where titration started -which is arbitrary. The percentile depends on where raising the pressure stopped and that depends on the disappearance of most apneas - which is not arbitrary.

It's not your breathing, nor is it the kind of machine you use nor its algorithm. It's a mathematical fact of life, and it shouldn't be overinterpreted.
O.

[rested gal]

Thanks ozij! Math always throws me for a loop. I can understand what you wrote (when I read it slowly and carefully...lol ) but I'd never be able to state it cold turkey myself!

I can, however, make a note of this thread for a future link if the question comes up again. Thanks for a very clear explanation, you math whiz, you!!

[ozij]

A math whiz I am not, but I did have to learn these things when I studied psychology - and I was so scared of the math, that I would come home from every statistics lesson, and copy everything I had scribbled in class onto clean pages. It was worth it.

Off topic:
I was very fortunate to have had that subject taught by two extremely talented people, talented both as teachers and as researchers: Daniel Kahneman and the late Amos Tversky. It was Danny's suggestion to all of us to re-write the summaries (and I had the wisdom to do as he said....). 30 years later, Daniel Kahneman got the Nobel prize in Economics - "for having integrated insights from psychological research into economic science, especially concerning human judgment and decision-making under uncertainty". Amos Tversky would have shared the prize if weren't for his untimely death.

O.

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[roster]

Rested Gal, Thanks so much for the information on GERD. Rooster

[arthuranxious]

I have had the strangest experience, I was titrated to 7 with the note on the report that it did not fully resolve the apnea problem.When I started AAPing merrily away the prssure was 7-9 the first month and then began climbing up and down until the 90th percentile rate was running between 9.5 and 11.6. This gradual process took place over many months, and I couild not find a pattern except gradula increase. I thought that it would be something to bring to my doctor's attention at my 6 month checkup in July and then in June it began going down again. last night was 8 the night before 8.6, I even had a 7.2 last week! Is this related to weather? eating habits, I am astounded to find that as the anniversary of titration draws near my pressuer are getting back to that level ...curiouser and curiouser ( as Alice in Wonderland observed)!