Is Too High Setting Harmful?

[Sheriff Buford]

I see my primary doctor next week and will request him to write a prescription for a S9 Autoset. I just talked myself into an autoset (knowing I can have the best of both worlds of cpap and apap). Two questions:

- My setting was originally set at 13 cm H2O. I bumped it to 14 cm H2O (with my current cpap machine) and I feel much better. Is there any health effects related to a pressure setting to high? Would it just be "wasted" air?

- What would be my auto set range? I'm thinking 13 cm H2O as the lower and 18 cm H2O as the upper. Keep in mind my primary care doctor is very uninformed and I never was referred to a sleep doctor.

On a lighter side, my primary care doctor is my brother-in-law. He has performed the "finger wave" on me. You have no idea what it is like to have a normal conversation with him a family function without me thinking of where his fingers were. Before he performed the task, he said, "Don't worry, I'm not enjoying this either!"

Sheriff

[Otter]

I have a lot to learn yet, but from what I've read, none of the common xpap machines can produce enough pressure to do more than annoy you. Here's an article you might find interesting.
http://www.cpap-supply.com/Articles.asp?ID=143

[techy]

Yes, too high of a setting may do harm...in some people they can cause Central sleep apnea...

[bayourest]

I am pretty new to all this but why dont you try setting it to 13-15 and see how you do?

[Sheriff Buford]

Thanks Otter... good reading...

[techy]

sorry,

here is a breif explanation of central apnea.... in some folks this will happen at a particular pressure, and they just cant go any higher....

Central sleep apnea — Central sleep apnea is a disorder in which your breathing repeatedly stops and starts during sleep due to lack of respiratory effort. Unlike obstructive sleep apnea, in which you can't breathe normally because of upper airway obstruction, central sleep apnea occurs when your brain doesn't send proper signals to the muscles that control your breathing. Central sleep apnea is less common, accounting for less than 5 percent of sleep apneas.

[DocWeezy]

Re centrals and higher pressure: that's why we have software! That way you can monitor what is happening. If you raise the pressure and suddenly start having a lot more centrals, then you know to lower the pressure. One or two nights of having more centrals most likely is not going to hurt you.

When I was adjusting my pressure, I discovered that I did get more centrals when the pressure went above 17 and I started waking up aware that I was holding my breath against the pressure. I lowered the top pressure to 16 and now only have the normal one or two centrals a night.

It's all about making small changes and then checking the software graphs to see what is happening. You're not going to hurt yourself by experimenting. Heck, even the doctors don't know at what pressure you may (or may not!) get more centrals--they also have to try things and see how an individual reacts.

Weezy

[Pugsy]

In general APAP won't try to go higher unless it senses a need to do so. Thus the range of pressures and possible higher max may be a moot point in regard to the max. Two things will drive the pressure up. Leaks and event needs. If the leaks are under control that leaves events as the reason for the machine to raise the pressure. Some people (like me) will occasionally have some super duper rogue events and need a significant pressure increase to deal with them. Some people don't. Some people find even minor variations of pressure (even APAP's little probes) disrupting to overall sleep. Some people don't. The trick is to have a minimum pressure that is comfortable and addresses the bulk of the "run of the mill" events but close enough to quickly address the other events.

APAP may not be the best choice if a person seems to have presser driven centrals. Straight cpap or apap with very tight range might be better (or even different machine depending on number of those events). If no history of centrals and no centrals showing up on data, then not much chance of apap wanting to go to a pressure that would possibly cause problems.

I use APAP settings 10 cm minimum and 18 cm max. If I lower minimum to 9cm I get the return of event clusters that do seem to stress my body so 10 works best for me and it is close enough to handle any rogue events. On occasion I have seen it go to 15 or 16 max and I can't blame it on leaks. So I know it didn't like something. Most of the time it stays around 11 and sometimes 12 and my AHI is often less than 1.

BTW my titrated prescribed pressure was 8. I think that was a poor titration result because I was documented much worse in REM and I simply didn't have enough time in REM to get accurate adjustment. Total time in titration study was slightly less than 3 hours and documented about 15 minutes in REM and even that was fragmented.

If you do well now at 13 cm you may find that a minimum of 12 and max of 15 (or more) will work well. Each person is different and your 13 or 14 cpap pressures could be a "worst case scenario number" and might get by with a little less minimum. Only way to know is to try some ranges and see which gives best results and lets you rest comfortably should you decide that you want to give the APAP a try.

[Sheriff Buford]

Thank you Pugsy. I will certainly let you off with a warning if you are exceeding the speed limit in East Texas!

[Otter]

BTW my titrated prescribed pressure was 8. I think that was a poor titration result because I was documented much worse in REM and I simply didn't have enough time in REM to get accurate adjustment. Total time in titration study was slightly less than 3 hours and documented about 15 minutes in REM and even that was fragmented.

One thing that puzzles me is why some people think that titrating for a few hours on a single night, when the patient isn't even in his or her own bed, is going to produce results that will apply at home, year round, under changing conditions. Yes, they've got EEG and EKG, and that's very useful, but they don't have your house, your bed, your pillow, your partner, the mold growing in your AC, etc.

It reminds me of this story.

One dark night, a man finds his neighbor, a scientist, looking for something under a streetlamp and asks if he needs help. The scientists says, "Yes. Thank you. I dropped my house keys." Both men search the area thoroughly.

After many minutes, the neighbor asks, "Exactly where were you when you dropped the keys?"

"Over by my front door," replies the scientist replies, gesturing into the shadows near his house.

"Well, then, why are we searching over here?" asks his puzzled neighbor.

The scientist gives his neighbor and odd look, then gives the answer that seems extremely obvious. "Because this is where the light is."

Now don't get me wrong. I'm not against science. I think it's very useful stuff. Nor am I against scientists. But one basic problem of science is that we can explore only the things we can measure with the methods and instruments that are at hand or within budget. This barrier constantly recedes as science and technology advance, but it's always there. And hence, we often wind up searching where we can see rather than where the real answers lie. That's not a bad thing. We do what we can do. But when we forget the limitations of our vision, we become fools.

[Wulfman]

I see my primary doctor next week and will request him to write a prescription for a S9 Autoset. I just talked myself into an autoset (knowing I can have the best of both worlds of cpap and apap). Two questions:

- My setting was originally set at 13 cm H2O. I bumped it to 14 cm H2O (with my current cpap machine) and I feel much better. Is there any health effects related to a pressure setting to high? Would it just be "wasted" air?

- What would be my auto set range? I'm thinking 13 cm H2O as the lower and 18 cm H2O as the upper. Keep in mind my primary care doctor is very uninformed and I never was referred to a sleep doctor.

On a lighter side, my primary care doctor is my brother-in-law. He has performed the "finger wave" on me. You have no idea what it is like to have a normal conversation with him a family function without me thinking of where his fingers were. Before he performed the task, he said, "Don't worry, I'm not enjoying this either!"

Sheriff

You know what they used to say......."If it feels good, do it."
If you don't have any Centrals at the pressures you're at, you probably aren't susceptible to them.

Once you get your new APAP and the software, you'll be able to figure out what your best pressure settings are.

Having a brother-in-law as one's doctor could be a "strange" situation......


Den

[rested gal]

Yes, too high of a setting may do harm...in some people they can cause Central sleep apnea...

I may be wrong but I don't think "too high" pressure will cause Central Sleep Apnea. Central Sleep Apnea is a disorder of its own, and a quite rare one at that....as you mentioned in your followup post, techy.

In your first post, you probably meant that high pressure settings can, in some people, cause some central apneas (not Central Sleep Apnea itself) to happen. That's very different from actually having "Central Sleep Apnea" (the disorder.)

There's also Complex Sleep Disordered Breathing, in which a person who doesn't have any (or not many) central apneas in the diagnostic sleep study has MANY central apneas when CPAP is applied. Centrals that persist. But CSDB (or "CompSAS) is still not the same thing as being diagnosed from the beginning with "Central Sleep Apnea" (the disorder.) And different from having a few temporary centrals pop up here and there when pressure is raised.

Back to plain vanilla OSA (Obstructive Sleep Apnea) which is what most people with sleep disordered breathing have -- I've read that even if some central apneas pop up when pressure is increased during a PSG titration, those "pressure induced" centrals are very likely to just be temporary ones, and are very likely to go away on their own if the tech simply lets the person stay at that pressure for awhile to give the brain and body some time to get used to that new pressure. Then the pressure can be raised some more, if need be.

In the case of people tweaking their own pressure settings at home, even if raising pressure might cause a few central apneas to happen in some people... would having a few centrals scattered throughout the night be worse than allowing obstructive apneas to happen in greater numbers? Simply because the person keeps reading "Watch out!!! Raising your pressure might cause centrals!!!!" (not that you were putting it that way, techy) and is afraid to raise the pressure another cm or two on their own to try to eliminate obstructive apneas and hypopneas...to get their treatment AHI under 5.0?

Some reassurances about the appearance of a few centrals -- in sleep studies AND in our CPAP therapy at home:

viewtopic.php?p=122303#p122303
Last paragraph in StillAnotherGuest's post at the bottom of 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

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viewtopic.php?p=154811#p154811
On page 2, from another post by StillAnotherGuest:

Assuming that the obstructive events are properly managed, then the likelihood of these being sleep-onset centrals is fairly high (you'd need PSG to be 100%) and those things are pretty much a normal event.

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viewtopic.php?p=428835#p428835
DreamOn quoted this passage from the book:
"Sleep Apnea: The Phantom of the Night" by T. Scott Johnson, M.D, et al.

"Small numbers of central apneas are seen in virtually every normal and abnormal patient that is studied in the sleep lab and are usually a normal part of the transition to sleep.
....
"We have an automatic breathing control system that maintains the carbon dioxide in our blood at a stable level. This system helps to control the rate at which we breathe....During the day when we are constantly overriding our automatic breathing, most people maintain their carbon dioxide level at a fairly low level. With the onset of sleep, however, the sensor mechanism that detects levels of carbon dioxide in the blood becomes slightly less sensitive and accepts higher levels of carbon dioxide....This change in sensitivity occurs quite suddenly as we drop off to sleep from a normal awake breathing state, and we suddenly do not have enough carbon dioxide in our blood to drive regular breathing during sleep. For this reason, at sleep onset and after arousals there is often a pause in the effort to breathe that may last as long as 10 to 15 seconds. These events may be normal."

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JohnBFisher wrote:

"Here's an article that discusses how central sleep apneas occur during sleep onset:"

Ventilation is unstable during drowsiness before sleep onset
http://jap.physiology.org/cgi/reprint/99/5/2036

viewtopic.php?p=457468#p457468

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christinequilts (who was diagnosed with almost pure Central Sleep Apnea -- severe case) wrote:

6 centrals is not a lot- less then 1 per hour, and is perfectly normal. Everyone has central apneas- take 3 or 4 very slow & deep breaths right now, then count how many seconds after the last inhale until you feel the need to inhale again. Was it more then 10 seconds? If it was, you just had a central apnea. Next time you sigh take note how long before you inhale again....yep, another central apnea. Yawn? same thing can happen. Pick up a heavy box or weight- did you remember to breath? if you didn't, then you had another central apnea. Think of what you hear exercise trainers lecture about breathing while exercising- its human nature to not breath when we exert themselves.

Of course all of these are awake apneas- but any time you don't breath for 10 seconds, you technically have an apnea. While sleeping, you can have similar things happen- you can take several deep breaths and not need to breath for several seconds. During transitions between sleep stages, it is common to have central apneas because the acceptable levels of O2/CO2 are different for each stage...sort of like when you're still going 55MPH as you enter the 35MPH zone. When you turn over at night, it is common to not take a breath- just like when you lift something or exercise when awake. In people with OSA, they don't consider centrals a problem until they are well above 5 per hour- central apneas can be a symptom of OSA, just like snoring, arousals, etc. A few centrals are nothing to worry about- most sleep labs don't get concerned about centrals unless there are a lot of them.

viewtopic.php?p=47781#p47781
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Also by christinequilts:

Having CENTRAL SLEEP APNEA, as a diagnosis, is rare. Having a few central apneas during the night isn't, its very common & is completely NORMAL.

viewtopic.php?p=179463#p179463

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More of christine's well informed comments:


THink about when you exercise or concentrate hard- if your not aware you can hold your breath which is essentionally central apnea. Turning over in your sleep is basically like an exercise- you go from doing nothing to moving. If you were to have your breathing monitored while you are awake you would see a lot of 'central' events.

viewtopic.php?p=15061#p15061
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and here, where Christine was accidentally "guested":

Most people- even those without sleep disorders- have a few central apneas while sleeping. A common cause is when you roll over...have you ever noticed when you're exercising or lifting something heavy that you hold breath unless you actually think about your breathing? The same thing can happen at night as you toss and turn. THere are other things that cause centrals too- there is a certain amount of variance in our breathing patterns when we sleep just like there is when we're awake.

I wouldn't worry about central events unless there were a significant number per hour

viewtopic.php?p=6176#p6176
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http://www.apneasupport.org/viewtopic.php?p=24677

In a reply titled "Nope" sleepydave (RRT, RPSGT and manager of an accredited sleep lab) 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", "NotMuffy", and "deltadave."

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[M.D.Hosehead]

RG, I'm repeatedly impressed at the amount of effort you voluntarily put into helping complete strangers. Thanks again for all the help you've given me.