Hello Guest, Welcome to Apnea Board !
As a guest, you are limited to certain areas of the board and there are some features you can't use.
To post a message, you must create a free account using a valid email address.

or Create an Account

New Posts   Today's Posts

Your AHI 12.9 was Horrible; See a doctor.
(02-24-2015, 04:17 AM)archangle Wrote: ...You're only fooling it because you're awake, which we know the machine can't tell.

...Are you talking about pressure induced central apnea? That's pretty well understood. CPAP pressure can cause your tidal volume and minute ventilation to increase. The increased minute vent can cause "washout" of CO2. Your respiratory drive is mostly based on your CO2 levels, not oxygen. Low CO2 makes some people stop breathing for a while until your CO2 picks back up and your respiratory drive makes you start breathing again. Another theory is that your lungs become more inflated and the stretch receptors in your lungs gives feedback that reduces your respiratory drive.

Google "Pressure Induced Central Apnea" and you'll find a lot of info.

What I found is this article:


Which seems to have some of the exact phrasing you are using in your post, which makes me think you might have read it, too. But what you left out is this:

"Clinical experience has suggested that these events resolve spontaneously over time, since ongoing CPAP therapy is not a recognized cause of central sleep apnea. The pathogenesis of treatment-emergent central apnea, however, is unknown and is poorly studied.5 Several theories have emerged, based largely on speculation."

And that would imply that it is not at all "pretty well understood".

What we can take from this is exactly what I suspected, which is that a pressure-induced central event is quite different from a spontaneous central event that is not pressure-induced.

Here is how I am interpreting this, and full disclosure will add that there is a lot of speculation in my theory:

Respiration is governed by a feedback system. While it is not as simple as this, essentially the body knowing what the 02 saturation is, is induced to automatically inhale when the saturation lowers to a particular point. CPAP pressure can mess with this in many ways, such as those you mentioned and are mentioned in this article.

But a central that happens without PAP can only have one cause, which is a failure of the feedback system. A pressure-induced central does not necessarily point to a failure of the feedback system, because the PAP skews the system's operation. The respiration system may actually be working just fine.

So a pressure-induced central event is very different than a normal central event, because one implies a problem with respiration while the other really doesn't, at least not definitively.

Failure to inhale is scary when you are the cause; not so scary when the therapy itself is ironically the cause.

If I am looking at this correctly, this supports my earlier statement that "the centrals are not coming from me, they are coming from the therapy itself".

I don't think there was ever a question about being awake while fooling the machine; the point was that I CAN fool the machine, and it is therefore not perfect and really not even all that smart. That I might have been awake while doing it is beside the point, but even so, it underlines how imperfect the machine is, if it is flagging events that aren't real and dithering the accuracy of the AHI report.

And this is a prime indicator of how smart the machine isn't, and how inaccurate AHI can be as a result: the xPAP can't tell the difference between a pressure-induced apnea and a non-pressure-induced apnea, two very different things that have very different indications as to respiratory health.

Instead, it lumps them both together and treats them the same, counts them as equals, and summarizes them in a single dumb AHI number.

As in anything else, it is always important to understand and have respect for the margin of error you are dealing with. xPAP isn't magic and we should not be sheep and assume it is perfect and that the AHI it is reporting is an ironclad certainty; xPAP is great and sophisticated, but still flawed.

Pressure induced central apnea is pretty well understood.

We know it happens. Demonstrated by many real world centrals happening in people who don't have centrals without CPAP or who don't have central apnea with lower pressure. Doctors have been balancing central apnea vs. obstructive vs. pressure for a long time.

We know it goes away for some people after a while, but not for others.

We have a couple of mechanisms that give plausible explanations for why it happens. We don't really know why one person gets it and another one doesn't.

We know reducing pressure reduces central apnea in most people who don't have central apnea without CPAP.

We have machines that detect it.

We have ASV machines specifically designed to treat it and they work fairly well.

Counts as "pretty well understood" in my book
Get the free SleepyHead software here.
Useful links.
Click here for information on the main alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check it yourself.
flip a coin, but in my book the data we are providing and the study lookups are certainly "demystifying" the CA OA H TV O2 PRS1 olallagramaticus for the new and slightly older CPAP high-performance users.

Thank you both and a half-dozen others that help in doing so.

Dedicated to QALity sleep.
You'll note I am listed as an Advisory Member. I am honored to be listed as such. See the fine print - Advisory Members as a group provide advice and suggestions to Apnea Board administrators and staff concerning Apnea Board operation and administrative policies. Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.

One more thing that most people overlook is that EPR/Aflex is a poor man's bilevel therapy. Aflex is a bilevel with Pressure support of 2. And EPR is PS of 1-3. Bilevel is used in hospital settings to washout CO2 more efficiently.

Also, when you initiate APAP, you are changing the pressure multiple times which can cause more CO2 washout and also more microarousals (you only see them on EEG but there is research out there which says that pressure changes can make you move from a deeper sleep state to a shallower state).

Also, our body takes time to adjust its TV and MV to adjust for a new breathing paradigm of IPAP, EPAP and PS. Even more time to adjust to continuously varying pressures of APAP.

I have finally turned my APAP to a CPAP with max=min=8cm H20 and Aflex set to 3. I sleep much better at AHI of (0.2 - 0.55) than I slept with APAP 7.5-14 with AHI of (0.0 on multiple nights). No headaches at all in the mornings. No crashes in concentration in late afternoons.

CPAP removes a lot of guesswork for the autonomic brain while sleeping.

I suggest everyone should try straight CPAP when you can tolerate your 90% pressure as start pressure.

Started APAP 4-20, Closed range to 7.5-14, then straight 8.0 w/ Aflex 3
RDI always below 1. But sleep much much better at straight pressure.
Started on F10, Tried Quattro Air successfully. Finally settled on P10.
Since the data is recorded regardless of whether you are awake or asleep, as Tyshoes points out, I've been wondering what (ahem) marital relations would look like when recorded... Is a "petit mort" as the French would say, interpreted as a CA?

There's some research you IT and data experts can conduct. Just tell your partner "It's for science"!
Have a good day!
(03-18-2015, 10:21 AM)trailrider Wrote: Since the data is recorded regardless of whether you are awake or asleep, as Tyshoes points out, I've been wondering what (ahem) marital relations would look like when recorded... Is a "petit mort" as the French would say, interpreted as a CA?

Don't forget rule 34!

Ed Seedhouse

I am neither a Doctor, nor any other kind of medical professional.

Actually you know, it is what it isn't.

Possibly Related Threads...
Thread Author Replies Views Last Post
  [Diagnosis] Was the doctor pulling my leg? Mordi 16 726 12-19-2016, 08:18 AM
Last Post: Mordi
  sending sleep study to another doctor's office sleepytimegal 3 313 11-30-2016, 10:26 PM
Last Post: Mosquitobait
  Sleepyhead data vs. Doctor's data Daisylouu 8 1,646 09-01-2016, 06:10 PM
Last Post: eseedhouse
  Horrible AHI John Turner 4 406 08-22-2016, 01:19 PM
Last Post: justMongo
Angry Doctor will not give my PX..need HELP Unloadit 27 1,217 07-19-2016, 02:09 PM
Last Post: justMongo
  First Appointment with Sleep Doctor sautee 31 1,760 07-07-2016, 07:43 AM
Last Post: OpalRose
  Doctor follow-up Inky1 6 629 06-06-2016, 11:50 AM
Last Post: green wings

Forum Jump:

New Posts   Today's Posts

About Apnea Board

Apnea Board is an educational web site designed to empower Sleep Apnea patients.

For any more information, please use our contact form.