Central Apnea caused by too high pressure / oxygen

[sydneybird]

Here is a quote from another forum:

"On standard CPAP at my titrated pressure I experience central apneas. Even during my last sleep study, under direct monitoring, I experienced central apneas. The CAs are induced by too much pressure, but not by the pressure alone, but as a result of constant pressure for an extended period of time. After a while at the constant pressure the body's tissues become saturated with oxygen, causing CO2 to decrease and initiating central apneas. "

Does it make sense that we would stop breathing (have central apneas) because of too much O2 due to too high a pressure? This makes zero sense to me since CPAP is not increasing the concentration of O2 of the air we breath. I have never heard of this cause/effect. Do those people at oxygen bars at the airport eventually have a series of CA's to let them know they have had enough?

This might be important for us DIY pressure changers. Do you notice an increase in CA's when you up the pressure? Over the past 6-weeks my CA's don't seem to correlate with a change in the 90% pressure range from 6-12 cmH2O (the CA's stay within the average 1-2 per hour nightly fluctuations), but my blood ox saturation has never hit 100%. Oxygen toxicity seems to occur only at elevated concentrations of oxygen (WiKi), which CPAP is not providing?

I suspect that too much oxygen is a non-issue for CPAP users even at max pressures and not a cause of CA's. What do you think?

[rested gal]

On standard CPAP at my titrated pressure I experience central apneas. Even during my last sleep study, under direct monitoring, I experienced central apneas. The CAs are induced by too much pressure, but not by the pressure alone, but as a result of constant pressure for an extended period of time. After a while at the constant pressure the body's tissues become saturated with oxygen, causing CO2 to decrease and initiating central apneas.

Gotta love those "this is a FACT" statements that some people indulge in as if they knew what they were talking about. I've been guilty of a few "this is how it is" statements, myself. But I do at least try to avoid doing it...and that's a fact!

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

[chunkyfrog]

Yeah, and when I was 12, I came up with a theory of nuclear attraction that specifies the fields around protons had gaps in them,which hook together at extremely close range; thus enabling nuclei to hold together. Sometimes an idea seems so logical, one forgets their qualifications do not match up.

[sydneybird]

So, standard treatment for CA's is CPAP and/or oxygen, but too much of a good thing ... you're right, the above quote makes no sense at all, thank goodness.

[HoseCrusher]

This is actually a very complex issue.

The body tries to maintain a PH balance. O2 and CO2 are part of this balance. Your respiration rate is in response to the body trying to maintain this balance.

The other side of this is your blood. Your blood can only hold so much O2. If you go to an oxygen bar, you can only get as much O2 inside your body as your blood can carry. The rest gets exhaled.

A crude example would be swimming. You hyperventilate, then have a CA while you dive in and swim underwater to the other side of the pool. OK, not the same, but the results may be similar.

I am not sure at all if this applies to xPAP therapy at all, but have read reports that seem to indicate that too high a pressure triggers centrals, so there may be something to this.

[tschultz]

My understanding of central apneas are that they are essentially when the body does not send the signal to actually exhale or inhale and therefore is different from an obstructive which is caused by a physical blockage of the air passage.

Central apneas can be caused in some people from CPAP or air delivery when the pressure or air flow is too high. This is due to the continual air being pushed into the lungs which can dilute the carbon dioxide in the vacinity of the chemical receptors within the lungs. Without detecting elevated levels of carbon dioxide signals, the brain does not then get the "message" that it is time to exhale. The normal breathing process bring air into our lungs on inhale, oxygen is transported to the blood stream and at the same time carbon dioxide is transported from the blood to the air which is then purged by exhaling.

It is my understanding that this possible impact on centrals is not a problem until pressures are over 10 cmH2O and certainly does not happen with everyone or we would all be in trouble. I know I am running at a pressure of 18 cmH2O and I have not seen any change in the number of centrals with the pressures from 13 to 18, and I have monitored closely for this when trying to optimize my settings/treatment.

It is common for everyone to have a small number of central apneas with or without CPAP or air delivery treatment(s), and for many these often occur towards the early part of their sleep and are commonly known as sleep onset apneas.

I'm certainly not a health-care professional so I may be wrong, but the above is based on what I have learned in my quest to better understand my OSA condition and its treatment.

[rested gal]

have read reports that seem to indicate that too high a pressure triggers centrals, so there may be something to this.

Right. That can happen. But, as someone who knows an awful lot about respiratory matters wrote once:

On page two of this thread: viewtopic.php?t=14225

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 is an RRT, RPSGT, and manager of an accredited hospital based sleep lab.

[WontGiveUp]

Here is a good article on Sleep Apnea from MedicineNet.com http://www.medicinenet.com/script/main/ ... f=3&page=1 It describes the different forms of Sleep Apnea well, including Central Apnea. Here is an excerpt from the artical:

"Under normal circumstances, the brain monitors several things to determine how often to breathe. If it senses a lack of oxygen or an excess of carbon dioxide in the blood it will speed up breathing. The increase in breathing increases the oxygen and decreases the carbon dioxide in blood. Some people with heart or lung disease have an increase in carbon dioxide in their blood at all times.

When there is a chronic (long term) increase in blood carbon dioxide, the brain starts to ignore the oxygen level and monitors the blood carbon dioxide level to determine when to take the next breath. The control of breathing also becomes slower to respond to changes in carbon dioxide levels; so when a person takes more or deeper breaths and "blows off" carbon dioxide the drive to breathe decreases and the rate of breathing decreases. As a result of slower rate of breathing, the carbon dioxide builds back up in the blood and the rate of breathing increases again. The brain, slow to adjust, continues to signal for more rapid breathing until the carbon dioxide level drops too low. Breathing then slows down or stops until the carbon dioxide level rises again. This pattern of abnormal breathing is called Cheyne-Stokes breathing (after the men who described it). It is characterized by repetitive cycles of fast breathing followed by slow breathing and apnea. This breathing pattern happens when the person is awake or asleep, but becomes more of a problem when asleep. Some patients with heart failure have central sleep apnea associated with a Cheyne-Stokes pattern of breathing."

Now in my own experience (not to say everybody is the same) I DO NOT HAVE Cheyne-Stokes breathing without being on CPAP, but I DO HAVE it while using CPAP. What I have discovered for me is I have it whenever I disrupt the flow from the exhaust on my mask by for example sleeping on my side with a fluffy pillow. What this does is cause carbon dioxide not to be exhausted from the mask and hose when I exhale. When I correct my sleeping position (something I constantly struggle with) than my CAs completely go away and I feel sooooooo much better in the morning.

Take care and I hope you figure out what's causing yours. By the way I discovered my sleeping position issues by "filming" myself many nights with a webcam.

[rested gal]

Thanks for posting the link and excerpt from that article, WGU.

What I have discovered for me is I have it whenever I disrupt the flow from the exhaust on my mask by for example sleeping on my side with a fluffy pillow. What this does is cause carbon dioxide not to be exhausted from the mask and hose when I exhale. When I correct my sleeping position (something I constantly struggle with) than my CAs completely go away and I feel sooooooo much better in the morning.

The Swift FX you're using may suit you so well in every other way that you wouldn't want to try a different mask. But if you do want to try another, you might like Aeiomed's "Headrest" with nasal pillows.
LINKS to HeadRest nasal pillows mask topics (same mask has had other names: Aeiomed Aura, then Headrest, then Invacare Twilight NP, then back to Headrest again.)
viewtopic.php?t=3098

Most people's initital impression at just seeing pictures of the Headrest would be, "No WAY!!! Ridiculous!!"
Don't be put off by its weird look. Looks heavy, cumbersome, awkward, uncomfortable. It's none of those things. "In person" it's remarkably lightweight and unobtrusive.

It's a great mask for sleeping in any sleep position -- back, tummy, even on one's side with the entire front of one's face buried against a fluffy pillow. That's how I sleep, too! What makes the Headrest mask so suitable for pillow-hugging side-sleeping is the location of the exhaust vent.

The vent is up high, almost at hairline level, well above the eyebrows. And the exhaust vents straight up -- not out in front of you. Like a little chimney. It's almost impossible to block the Headrest's vent. Unless you stood on your head in bed. But, I think you'd have caught that in your video of yourself sleeping.

By the way, if you ever try the Headrest and don't like it, PM me. I would buy it "used." I'm still adding to my stash of Headrests to last me the rest of my life.

[sydneybird]

But if you do want to try another, you might like Aeiomed's "Headrest" with nasal pillows.
The vent is up high, almost at hairline level, well above the eyebrows. And the exhaust vents straight up -- not out in front of you. Like a little chimney. It's almost impossible to block the Headrest's vent. Unless you stood on your head in bed. But, I think you'd have caught that in your video of yourself sleeping.

Lately with my EasyLife mask I have been awakened many times with one of my arms being really cold from the exhaust blowing on it. With the exhaust being on a swivel elbow and the hose either going off to the side or over my head, it could hit my left arm, the blankets over my chest, or my right arm depending on how I am laying. I'm finding that I have to encase by entire body up to my neck and arms in to be sure the exhaust doesn't wake me up. I like to sleep with my arms outside of the covers so this is a problem. At least the dogs (see avatar) aren't sleeping under my chin anymore. I really hope to try the Headrest some day, but worry that availability will be limited with what is going on at Aeiomed. Their website gives me no confidence that I should invest in the mask (no insurance). I have a ComfortLite 2 coming any day now and wonder how the exhaust is. The exhaust area looks to be at least twice the surface area as the EasyLife so that should help to reduce the velocity of the exhaust.

[rested gal]

I really hope to try the Headrest some day, but worry that availability will be limited with what is going on at Aeiomed. Their website gives me no confidence that I should invest in the mask (no insurance).

I agree. I have no DME insurance either. From day one when I found the Headrest to be the best mask I'd ever used, I started collecting extras whenever I could. I didn't have confidence even then back some years ago, that a small start-up company would be able to last against the big manufacturers. Especially with a mask that was such a turn-off in appearance, no matter how well it worked. Aeiomed's real claim to fame was their cool battery option CPAP machine, and even that probably didn't catch on as well as it needed to with bricks and mortar DMEs. The DMEs are so used to placing their machine orders with the big guys who court them heavily.

One other good thing about the Headrest... its nasal pillows are very long lasting. Probably much more so than most other brands. The nasal pillows I'll be using with it tonight are the same ones I've been using for well over a year now. They just don't wear out or lose their oomph like some other brands' nasal pillows seem to do.

Another plus -- when I add my homemade strap to cradle the pillows up to my snoot, I can wear either size pillows that come with it -- the medium and the large pillows. The "medium" fit me well, but the large work too. The pillows are just smushy enough to be comfortable without being flimsy, so the homemade strap keeps the large pillows in place perfectly, too. So every Headrest I acquire is like my getting "two for one."

I'm well supplied to at least age 80. A lot more masks should come out between now and then. Perhaps another one someday with an exhaust like the Headrest's.

[sydneybird]

rested gal, thanks for the post. Great to hear about the longevity of the pillows, had no idea, with some other brand pillows lasting a few weeks. I'm going to keep my eye out for a Headrest.

[rested gal]

sydneybird, I keep forgetting to mention how much I like your avatar pic of your two adorable little dogs. I used to show dogs; now board and groom dogs. You've got a pair of real cuties there.