Recognizing Central Apneas

[Justin_Case]

Oh wise ones here on cpaptalk.com...please tell me how a PSG detects central apneas and if it can detect ALL central apneas. And most importantly, can central apnea be treated?

I have been deliberately holding my breath while testing my APAP machine. I notice it ramps up...I look at the software data and it shows I am having obstructive events during this time, which really makes me think I may have combination apnea, even though my sleep doc (who is a $#@) arrogantly says that's unlikely.

[tohosa]

I'm an amateur and a newbie, but I feel bold! Someone will surely correct me. What I learned from reading around on the Web after my first sleep study -- which showed about 1/3 of my apneas as central.

Unless you have a brain stem injury, you most likely don't have central sleep apnea. Your central apneas probably result from hyperventilation, sighing, etc.

The machine counts as an apnea any period of 10 seconds when you don't inhale. If you don't inhale for 10 seconds and you struggle to breathe, that's counted as an obstructive apnea event. If you don't inhale for 10 seconds and don't struggle, that's counted as a central apnea event. If you take a deep breath and don't need to inhale for more than 10 seconds, that's counted as a central apnea. If you sigh and don't inhale again for more than 10 seconds, that's counted as a central apnea.

If CPAP makes your "central" apneas go away, then they were obstructive in the first place. Something like that. I think.

[Snoredog]

they look at the EEG and respiratory channels to determine if it is a central.

So your machine cannot detect them. If you have a obstructive apnea that lasts 48 seconds and you have a central apnea that lasts 48 seconds, they look identical to the autopap machine. The reason is there is no air flow in either case.

The same scenario can be played out with hypopnea, only difference is there is a 50% reduction to flow and at least a 3% drop to oxygen levels.

The don't really know what causes central apnea. They suspect lesions found on the brain stem may contribute to the disorder but even that is not concrete.

Resmed is trying to address it by manipulating chemoreceptors and playing with CO2 levels. The human body seems to have many redundancies for critical functions so I don't think there is any one item that can be manipulated by a physical machine to resolve it.

Your brain's survival is the most critical function of your body, when you think about it every other organ's job is to support the brain. It is why your brain has 4 separate paths to supply it with oxygenated blood. These 4 join at the circle of willis where it is dispersed throughout the cerebral arteries.

My theory on pressure induced central apnea; is the cpap pressure inflates your lungs triggering the stretch receptors response which in turn sends the signal to the brain to cease respiratory drive, the result is the cessation of breath or central. Now when you have a central voluntarily on your own without cpap pressure then I would suspect one of the other receptors.

Most obstructive events will be eliminated with pressure, if they are central they will increase with pressure. This is why there is not many machines to treat it, there are machines to jump-start the respiratory drive if you stop breathing, but nothing that addresses the central itself.



They will probably find it some day, but money will drive that finding.

[Justin_Case]

Oh boy....that's not good. However, this may be the reason in my case.

During a sleep study is the EEG used in determining if the events are central? My understanding is that during a PSG, it only measures and records four forms of brain wave activity - alpha, beta, delta and theta waves?

[Snoredog]

Oh boy....that's not good. However, this may be the reason in my case.

During a sleep study is the EEG used in determining if the events are central? My understanding is that during a PSG, it only measures and records four forms of brain wave activity - alpha, beta, delta and theta waves?

If central apnea was seen on your PSG it should be noted under CA or MA events.

IF those exist on your PSG then you must rely on the pressure found by the PSG tech and NOT exceed that pressure with any autopap setting. The reason is the machine can confuse a central apnea for a obstructive actually scoring it as such which results in a pressure increase which makes the condition worse. You can almost do anything you want with the Min. pressure but the Max would have to be limited to the pressure found during your titration. This way your autopap never exceeds the pressure found during the titration even if it did confuse a central apnea for an obstructive one. Same can play out with hypopnea. Autopap mfgs try to write the algorithms to avoid that confusion but it is not fool proof.

Your Remstar would handle this situation better than some of the other autopaps, it has a limiting factor built-in to its pressure responses in an effort to avoid responding to a central. Any response is limited to a 1.5cm increase, if the event still exists it will pause with that detection circuit response. Also what helps is how it responds to snore. Snores can cause the machine to increase pressure, if that response was left unchecked that response to snore can trigger central type events.

I suggest:

1. Drag out your original PSG and study it carefully.
2. Drag out your titration study and study it carefully.
3. You should make note of any chronic snoring, CA or MA events.

What was your pressure found during the titration and exactly how do you have your machine set up?

[Justin_Case]

As usual, thanks Snoredog for the great info. My sleep doc never gave me the actual PSG report. I asked for it at my last visit about 3.5 weeks ago and he said he'll send it to my GP. My last PSG was done almost 3 years ago. I do think things have changed since then. I have another PSG coming up at the end of January. I'll call the hospital up next week to put me on a waiting list for a sooner session.

The oddest thing which I have been posting about for a while now is that my OA events are very high in the hours around 4AM to waking up. Typically, during my PSG, I am out of bed by around 5AM and I believe these high events were either not present at this time or I didnt have any OA then. My pressure setting has been a bit higher lately due to the stats in my Encore Software. Tonight, I will lower them to 10-13. If you like, you can see a copy of my results in spreadsheet form: http://www.freefilehosting.org/public/22896/CPAP.pdf

Just like to add, I have been referred to a neurologist for tingling sensations and because my substitute doc (GP) has done some touch tests on me and she discovered that there is some slight numbing on my right side...i have been trying to tell my GP for the last month and half that I need to see a neurologist, he didnt think so. Can't wait to "talk" to him when he returns in a few weeks. I can't help if this all is somehow related.

[ozij]

Justin, I'm very glad you posted that pdf. I created the following chart of you APAP usage, using a excel pivot chart.


(Many thank, Rested Gal for hosting the file on your site)

Two things stand out clearly:
The longest time you spent in any min-max pressure combination is 3 (three!) nights - and that isn't even necessarily three nights running. (You can see that in the purple columns). I would stick to one combination for a week at least, preferably two.

The second point is that the only time your AHI is under 4 is when your minimum pressure is 8.5 or ten, and when your max pressure is no more than 13 or 14.

Given that data, here's what I would do: either leave the machine at min 9 max 13, or min 10 max 14 for two weeks, or keep it on straight cpap at 10 for two weeks.

You are not letting your body get used to the therapy by switching around constantly.

Psychologicall, you must decide not to monitor the machine's functioning as you try to sleep. Try to sleep - think of it as a vacation from monitoring the cpap, think of it as 2 weeks you're going to waste - whatever you want, but let go of those attempts to control the machine and your breathing.

O.

[Justin_Case]

Thank you ozij for taking the time to look at my stats and post the chart.

What the stats don't show, unlike in the graph that shows the flags is that there are clusters if OA events during the hours around 5 AM until I wake up, which tend to drive the AHI up big time. The concentration is mainly in these areas, except for the other night which seems to be a bit more throughout. I will post the chart (the site is a little slow): http://img503.imageshack.us/img503/1479 ... 010wz8.jpg

and last nights number were high too where I lowered the min and maximum but again, a very high concentration of events post 5AM and leakage was up too:

http://img503.imageshack.us/img503/4507 ... 011qf0.jpg

[rested gal]

please tell me how a PSG detects central apneas and if it can detect ALL central apneas

The belts that were put around your chest and abdomen during your PSG sleep study detect "effort"...detect whether you are TRYING to breathe or not.

Obstructive apnea - the belts recorded movement of your chest or abdomen while the pressure transducer or thermistor (the little thingy you were wearing at your nostrils) recorded no airflow. Physically trying to breathe, but to no avail, because of the obstruction.

Central apnea - you were not trying to breathe (the belts showing NO movement...no physical effort) while the pressure transducer or thermistor recorded no airflow. Brain was not signaling the body to try.

I think the belts would be very accurate at showing if a Central was happening. If the belt is too loose or slips, I'd say it would be possible for it to look like a central when one really didn't happen. In that case, I'd think taking a look at the airflow would show that the person was still breathing despite the belt indicating they weren't.

Justin, I may be wrong, but I'd think that deliberately holding your breath while awake and using an autopap should eventually register as an Obstructive apnea (if you can hold it long enough)...not as an "NR" (suspected central) on the Encore Pro data. I'd think that most people deliberately holding their breath are muscularly closing off their own airway. Obstructing their own airway.

I doubt that most people who were awake could deliberately hold their breath long enough for the Respironics autopap to go through the 3 increased pressure nudges it needs to do before finally marking an even as an NR on the data. One pressure increase, yes, but to wait it out through the 3 increases...that would be very difficult to endure consciously, imho.

[Justin_Case]

Thanks rested gal, I have done that, held my breath and my APAP's pressure rose. Therefore, in addition to my nerve issues, it is my belief that I am having centrals around 5AM onwards. This, I believe will be difficult to prove since I am kicked out of bed at the sleep lab around this time and my opinionated and arrogant sleep doc won't allow me to have an extended session by staying longer.

[rested gal]

Sorry that I was editing my post at the time you were writing yours, Justin.

My edit, before I saw your next post, was to add this:

"I doubt that most people who were awake could deliberately hold their breath long enough for the Respironics autopap to go through the 3 increased pressure nudges it needs to do before finally marking an even as an NR on the data. One pressure increase, yes, but to wait it out through the 3 increases...that would be very difficult to endure consciously, imho."

[Guest]

My edit, before I saw your next post, was to add this:

"I doubt that most people who were awake could deliberately hold their breath long enough for the Respironics autopap to go through the 3 increased pressure nudges it needs to do before finally marking an even as an NR on the data. One pressure increase, yes, but to wait it out through the 3 increases...that would be very difficult to endure consciously, imho."

I did it through 1.5, maybe 2 a while ago....and yes, it wasn't easy but it was adjusting in .5 cm increments.

[christinequilts]

I doubt that most people who were awake could deliberately hold their breath long enough for the Respironics autopap to go through the 3 increased pressure nudges it needs to do before finally marking an even as an NR on the data. One pressure increase, yes, but to wait it out through the 3 increases...that would be very difficult to endure consciously, imho.

Can I try? Actually, your description of the breath holding being "muscular" seems pretty accurate, in my experience. When I've woken up in the middle of CA, its almost a surreal experience. Its so different then the struggling to breath, and sometimes even panic, people tend to experience if they fully wake up in the middle of an obstructive event, still not able to breath. On the few occasions I've woken up during a central event, breathing is the last thing on my mind; I start going through the checklist of 'why the heck am I awake?'...cats aren't running laps on my bed, don't have to pee, nothing hurts or feels funny, no dogs barking, TV not on, no alarm clock going off, not too cold, not too hot, no thunderstorm, etc. By the time I get through all the possibilities, I know several breathing cycles have taken place, as I've heard my BiPAP ST switching from IPAP to EPAP, but, oh yeah, there is something I'm suppose to be doing when it does that, isn't there? Like maybe actually BREATHING the air into my lungs, not just letting it air condition my nose Totally different then all the tension and struggle you feel when you hold your breath for more then one or two breath cycles to simulate a central.

[Snoredog]

Justin:

I just looked at your data. I glaced at all the data but zeroed in on 8/24 and 10/03 both showing NRAHI indicating the machine detected central apnea.

Note: The NRAHI is what the machine SEEN. You have no idea of the remaining AI and HI that the machine confused as being obstructive when they can equally be central.

On days 9/18 thru 9/24 where you let the Max. pressure run up a bit and the NRAHI went up accordingly. If you are at risk of having central apnea that is pressure induced that is what I would expect to see.

Then I scrolled to the right and looked at Maximum leak rate, you are 163-164L/m on some nights. On nights that your leak exceeds 75L/m you might as well toss out that data including any NRAHI seen.

From that leak rate, I would suspect mouth breathing with a leak rate that high. Your high AI score would also seem to confirm that (now watch I'll see you are using a Full Face mask and you can toss out that theory, but if not it is probably right on).

You need to understand one very important point:

1. Too much pressure can cause pressure induced central apnea, even below 10.0cm pressure.

Then looking at your AvgP it is running 7.7cm, to 9.5cm. Get any higher than 9.5 and you start having more NRAHI. That means you need to stay below 9.0cm or risk triggering central apnea.

Next, you still have a high Apnea Indice at 9.0cm pressure, but if you look at Max. leak rates they are as high as 164L/m. Meaning, you are mouth breathing and/or developing LARGE leaks where the machine CANNOT address the Apnea when seen (reason for the higher OA scores at 9.0cm).

Wrong machine: I see no reason why you should be on a Bi-pap machine, your pressure requirement doesn't warrant its use. A bi-pap machine is no better at avoiding central apnea than a autopap is. I would not doubt if half of those Hypopnea scored in your data are not central hypopnea. Same for the obstructive apnea being scored. If there is no associated Large Leak with those higher OA scores, they can also be central apnea listed in your report not obstructive.

Based upon your data, you should be on a straight cpap @ 9.0cm pressure. If you want to use Cflex that is fine.

You cannot use Autopap, the machine cannot read you for whatever reason. It is not the changing pressure it is the machine cannot determine correctly what type of events they are. If it confuses only 1 or 2 of those centrals as obstructive it will store that data in pattern memory, then respond with pressure the next time around it sees that same pattern making the condition even worse. When it scores a NRAHI it discards that pattern data so it won't be used next pattern and increase pressure.

But as I have said before even with the best algorithms these machines are not very good at detecting central events.

Again, I don't know what mask you are using as I type this, but from the data I'd say you need a Full Face mask and to reconfigure your machine.

1. Set machine to cpap @9.0cm
2. Stop mask leaks/or address any mouth breathing.

Try it for a few nights, study the results.

[rested gal]

but, oh yeah, there is something I'm suppose to be doing when it does that, isn't there? Like maybe actually BREATHING the air into my lungs, not just letting it air condition my nose Totally different then all the tension and struggle you feel when you hold your breath for more then one or two breath cycles to simulate a central.

How very interesting, Christine! Thank you for the clear description of how it feels to awaken fully during a central.

I do hope you'll describe every detail of your ASV titration soon! I'm sure you know how many of your well wishers and supporters want to hear everything about how that looks from your extremely experienced perspective.

Best of luck if that's still ahead! Hope the machine performed some wonderful magic for you if the titration night has already happened.

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