Newbie question-elaborate on pressure-induced central apne

[cpapthomas]

I just read in the newbie section. It said to be careful....."IF YOU GO 2 OR 3 ABOVE YOUR TITRATED PRESSURE IT IS LIKELY TO LEAD TO A PRESSURE-INDUCED CENTRAL APNEA. Can you explain to me in detail what actually takes place and what is pressure-induced central apnea? Thank you. All the best.

[who]

I just read in the newbie section. It said to be careful....."IF YOU GO 2 OR 3 ABOVE YOUR TITRATED PRESSURE IT IS LIKELY TO LEAD TO A PRESSURE-INDUCED CENTRAL APNEA. Can you explain to me in detail what actually takes place and what is pressure-induced central apnea? Thank you. All the best.

Well, I'm not sure I agree with the statement in the newbie section. I would say, "If you have a tendency to have a lot of central apneas, you may do best using a single, well-titrated pressure or using a machine designed to deal specifically with central apnea."

For someone with pure obstructive apnea, the idea is to apply only the amount of pressure needed, but that is mostly a comfort concern, not a medical concern, unless a person has a condition beyond simple obstructive apnea.

If a person has a machine that gives efficacy data, the person (or the clinician) adjusts pressure only high enough to improve the numbers for the person to feel better. If an increase in pressure increases AHI, or leaves it the same without improving how a person feels, then the natural thing to do is to lower the pressure back down, since there is no reason to have raised it.

There are sleep docs who will add on 1 or 2 cm of pressure to the Rx, just in case the sleep lab caught the person on a good night instead of a bad one. So a little more pressure should not be a danger to someone with everyday obstructive sleep apnea. Too low of a pressure would be a more serious problem than too high of one. The exact right amount of pressure would be the best thing, of course, for anyone.

It is true that increases in pressure can induce central apneas in some people, but they are generally harmless and usually go away with time (the central apneas, that is, not the people). There are better things to worry about than inducing some pressure-related centrals, if all you've got is obstructive sleep apnea, in my opinion. That's why APAPs with the maximum set to the ceiling are considered safe for OSA patients.

Does that help, or just cloud the issue more?

You said "in detail," so here is some deeper information discussing the differences, and similarities, when it comes to obstructive apnea and central apnea. It shows that things can get "complex."

http://assets0.pubget.com/pdf/pgtmp_08f ... 0962e1.pdf

[rested gal]

Well, I don't think 2 or 3 cm (or even more) increase in pressure over a "prescribed pressure" is likely to cause central apneas -- not for most people on CPAP. Just my opinion. Sure, it could. For some people. But I don't think that would happen for most cpap users.

And even if an increase in pressure produced a few random centrals -- no big deal.

If an increase brought on a lot of centrals that wouldn't subside even if the brain/body was given some time to get used to the new pressure, then yes, the pressure may unnecessarily high. How much time would it take for the brain/body to get accustomed to the change to a higher pressure and the centrals to stop happening, if it's ever going to get used to it? Might take just a few minutes. Might take several months. Might take even longer. Might never get used to it.

CPAP therapy can involve some tradeoffs. For some people it might be much better to accept a few scattered short central apneas (which may go away completely over time) in order to prevent a great many obstructive apneas.

But I'm not a doctor.

Links to Central Apnea discussions
viewtopic.php?p=22702

Note especially this, in the "Central Apnea" discussion link:

At another apnea board:
http://www.apneasupport.org/viewtopic.php?p=24677

In a reply titled "Nope" sleepydave (RRT, RPSGT and manager of an accredited sleep center) responds to honda's question:

honda wrote:
"Thanks for the comments, one other question though, do the 4 central apneas have any significance ?"

"None whatsoever.
sleepydave"

sleepydave's nicknames on cpaptalk are "StillAnotherGuest" (SAG) "Muffy" and "NotMuffy"

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Regarding concern about "pressure induced centrals"

viewtopic.php?t=14225
Page 2


The phenomena of pressure-induced central apneas is tossed around far too freely. The vast majority of people do not get centrals because of ultra-therapeutic CPAP levels. BiLevel, Pressure Support (PSV) and Proportional Assist (PAV) Ventilation are another matter. You need some mechanism to drive the pCO2 below the sleeping apneic threshold, and plain old CPAP rarely is able to do that. OK, if you wanna argue that CPAP increases base lung volume (Functional Residual Capacity)(FRC), and since that increases gas exchange, some people can generate centrals that way, fine. But it's not as many as you might think.
SAG

SAG ("StillAnotherGuest" is also "Muffy" and "NotMuffy" on cpaptalk and "sleepydave" on another board.)