How do higher pressures lead to Central Apneas

[mon]

I am confused as to why setting the pressure higher may lead to central apnea.

[Guest]

My suggestion is to do a Google search on "pressure-induced Central Sleep Apnea".......and then start reading.

One of the first few links will be to a thread on the Apneasupport forum by "sleepydave" who is also "deltadave" on this forum. The date on the thread is: Tue Jul 04, 2006 9:05 pm. I would suggest including that one in your reading.
Dave runs a sleep lab in a state in the northeast part of the U S and is extremely knowledgeable about sleep disorders. With any luck, he may chime in here if you have further questions.

My (simplistic) understanding of it goes something like this: Central Sleep Apnea is a neurological disorder. Our drive to breathe is controlled by CO2. Too much pressurized air can wash out enough CO2 that our brain fails to tell our body to breathe. There's (supposedly) only about 15% of the XPAP users who MAY be susceptible to this phenomenon.

The old ResMed APAPs had the A10 algorithm which would not chase events above the pressure of 10 cm. due to their studies that most pressure-induced Centrals occurred above the pressure of 10 cm.

Hope that helps.

.

[Pugsy]

Higher pressures don't lead to central apneas for everyone. Some people will have pressure induced centrals even at really low pressures (like 6 or 7). It isn't so much the actual pressure being "high" as it the body's response to the pressure (any pressure) in general. The body's balance of oxygen and carbon dioxide and that balance being out of whack and the brain thinking it doesn't need to breathe.

This video helps explain it somewhat.
https://www.youtube.com/watch?v=CU-XTcf ... e=youtu.be

I use an auto adjusting pressure machine and I push 20 cm fairly frequently yet I have no more centrals with that pressure than I do a my overall average of 12 cm. Some nights I see 19 cm with zero centrals. So higher pressures don't equal more centrals for everyone. There is a small percentage (10 to 15) of people who will develop centrals with cpap pressure (whatever pressure) so it isn't nearly as prevalent or as likely to happen and people tend to think.

[mon]

Thanks Guys,
I will follow that up.

[Slartybartfast]

Also look up "Hering-Breuer reflex." The Reader's Digest answer is that stretch receptors in the lungs sense that the lungs are already full.

[The Sheikh]

Question: Could the following be another reason why higher pressures cause centrals to increase in some people?

During the day, and possibly at night, I "forget" to breathe, for whatever reason. At night, according to the flow chart, I notice most of my centrals start right after I inhale. Then I hold my breath for up to 95 seconds. During a central, my lungs seem to have little drive to exhale. If my epap min is set much above 4cm, my centrals get really bad. (Using an ASV machine)

(BTW, my lung muscles are healthy since I can play a saxophone quite easily.)

Would CPAP back pressure just make this situation worse so that the already weak exhalation cycle is further retarded by the pressure and even cause breathing to stop?

Let's take an extreme example to emphasise the point: Let's say a healthy person was working against a 60 cm/h20 pressure. It would be near impossible to exhale. Now maybe a person who was already on the borderline with zero pressure would find exhaling against 10cm H2O a real problem when the brain goes into the central mode. (Assuming the central was caused by something other than the CO2 regulation system)

Does this make any sense?

Tom

[purple]

Folks with MS/MD sometimes have lung-muscles which are not physically able to exhale against higher pressure. A number of people can have other health issues where they can not exhale against pressure.

[Slartybartfast]

"Forgetting" to breathe is one thing. Pressure-induced non-obstructive apneas (Resmed calls them Centrals but they're not) are something else; they're the result of your lungs telling your nervous system that they're already full. Two different causes.

[purple]

Slartybartfest, can you elaborate on some of the differences between central versus other, does not continue to breath, and define if there is any difference in how they should be treated?

[The Sheikh]

"Forgetting" to breathe is one thing. Pressure-induced non-obstructive apneas (Resmed calls them Centrals but they're not) are something else; they're the result of your lungs telling your nervous system that they're already full. Two different causes.

In my case my lungs ARE already full after taking a breath and then stop - so the lungs are reporting accurately to the nervous system. So why don't they exhale?

Could low brain signal "drive" against the CPAP pressure be the cause? (Other than CO2 related)


Tom