Central events and Amplitude modulation radio

I am not sure how to post images so I hope the verbal explanation will be clear enough.

I noticed an interesting pattern around central events. Normal sleep-breath is fairly regulated - the length of each cycle is about 3-5 seconds and the amplitude is practically unchanged. However, in the vicinity of central events, the amplitude of the breath gets modulated by a lower frequency that has a full cycle of about 15 breath cycles (in my particular sample). The result is very similar to the electrical waves used in an AM radio. There is a carrier wave (e.g. the regular breath cycle) and an information (sound with the radio and “something” for the breath). Anyone familiar with electronics knows that when the modulating amplitude is higher than the amplitude of the carrier wave, the combined amplitude must cross zero in every modulation cycle. This is exactly what I can see on SleepyHead. What I can also see is that sometimes the modulation is not so deep, so the breath does not stop and the software does not record an event. In a specific sample (no pictures, sorry), the modulation was deep enough twice to record a CA event, but not so deep in the other, very close by, times so two potential CA events were skipped by the software.

My conclusion is that the CA event is not a standalone event. It is not that the brain decides to pause breathing for few cycles. Instead, the brain goes through a much longer cycle that involves gradual increase in the amplitude of the breath followed by a gradual decrease in the amplitude, until the amplitude becomes zero, and the cycle restarts.

I don’t have the tools or the knowledge to identify why the breath becomes suddenly modulated. I wonder if anyone has some input about that.

By any chance, are you talking about the Forced Oscillation Technique (FOT) that is used by the S9 machines to detect open or closed airway?

The FOT of 1 cm amplitude at 4 Hz looks like the following graph, in my machine, while detecting a central apnea 28 sec long in duration.
At such a time the machine will not raise pressure.

DannyCPAP wrote:I am not sure how to post images so I hope the verbal explanation will be clear enough.

I noticed an interesting pattern around central events.

I think you just described periodic breathing, which commonly results in central apneas.


The waxing and waning of flow amplitude are the result of loop-gain greater than one in central control. See the sections called VENTILATORY CONTROL STABILITY as well as CENTRAL SLEEP APNEA PATHOGENESIS in this document:
http://ajrccm.atsjournals.org/content/172/11/1363.full

Although periodic breathing is commonly associated with heart conditions, most patients who present periodic breathing probably do NOT have heart problems. Sometimes the condition is a side-effect of CPAP therapy. When it is---and severe enough---that condition is called CompSAS. Often that side-effect goes away after a month or two of adaptation to CPAP.
http://www.chestnet.org/accp/pccsu/comp ... a?page=0,3
http://ajrccm.atsjournals.org/content/1 ... 9.abstract

And sometimes periodic breathing with central apneas are the result of somewhat ordinary oscillations in central control--- associated with wake-to-sleep transitions in CO2 homeostasis itself:
http://jap.physiology.org/content/99/5/2036.full

While using the SleepyHead software you can see in the fllowing graphs, taken by the poster Papit, that the FOT is super imposed
on the respiration wave while detecting apneas:



You see it both in the flow rate and the mask pressure graphs.

Here are Pugsy's image posting intrructions:

We have to host them on a website and link to them.
I use screen shots and Photobucket because I found it super easy but other use different methods.

This is my standard "how to post images of reports" speech.


Open the image to full size so it is easily read.
I use Vista snipping tool to create a screen shot and crop the image at the same time.
Prt/scr key will also take a screen shot if using XP. If laptop is used sometimes the Fn key has to be pushed at the same time as the prt/scr key
I think windows 7 Home Premium has the snipping tool, Basic may not.

Once the screen shot is created save it in jpg format.
Upload the image to a host site. I use Photobucket it is free, there are others.
Once the image is uploaded then copy the ENTIRE IMG address. Be sure to include the opening and closing IMG in brackets. Paste that copied address into a post here.
Use the preview button. If you can't see the image try again because if you can't see it we can't.

Glad you posted that, AVI. The original poster will recognize FOT's short and constant amplitude pattern--- if that's what he's actually seeing on his reports. However, the poster described amplitude modulation (AM), which is a dead ringer look-alike for periodic breathing:
https://www.google.com/search?hl=en&tok ... qgGmq5CLCQ

Here's another visual reference picture for periodic breathing:

Danny, on your machine (in CPAP mode) and ResScan you can check if you have Cheyne Stokes respiration as this poster did:
Notice the waxing and waning.




And also for Periodic Breathing:

Notice the repeating wave patterns.



-SWS, I am showing Danny actions that he could take to find out. Thanks for your text material.

Good work, AVI. Cheyne Stokes respiration is a type of periodic breathing.

-SWS wrote:Good work, AVI. Cheyne Stokes respiration is a type of periodic breathing.

A simpler way to find out if a person suffers from any CSAS components could be to use ResScan, for example, to show the Stats over a period
of a month or longer. My question is if the shown results are some kind of averages?

Example (in CPAP mode, I think):

Thank you for the responses. Here are my origianl images

Danny, can you try to show the apnea and the wave graph in a 5 min total scale and including the events (synchronized).

Like this:



If it is something like this then it could be a Sheyne Stokes respiration (CSR).

-SWS wrote: http://www.chestnet.org/accp/pccsu/comp ... a?page=0,3

Quoting from the article "While obstructive events respond well to continuous positive airway pressure (CPAP) therapy, the response of central events is often incomplete and not sustained over time. CPAP treatment of obstructive events can, itself, lead to the development of central sleep apneas (CSA) or a Cheyne-Stokes respiratory (CSR) pattern in some patients."

I assume this is an insentive to keep the pressure to the lowest rate that blocks obstructive events, so as not to cause development of central Cheyne-Stokes events.

avi123 wrote:Danny, can you try to show the apnea and the wave graph in a 5 min total scale and including the events (synchronized).

Avi, it is practically the same as the previous picture. The events are marked by the vertical lines and "CA".

avi123 wrote: If it is something like this then it could be a Sheyne Stokes respiration (CSR).

http://thorax.bmj.com/content/53/6/514.full
"patients with Cheyne-Stokes respiration sufficient to cause symptoms have more than 20 apnoeas and hypopnoeas per hour sleep and should be considered for treatment."

Danny, those central apnea (CA) events that you describe are regarded as emergent CA, and you're correct about keeping the pressure as low as possible but still take care of obstructive events, snoring, and flow limitation. -SWS came in with Sheyne Stokes respiration and Periodic Breathing types of CSAS, which are different then those emergent CAs. I don't have any types of CSAS, but could get emegent CAs events if I raise the pressure.

In my case, as soon as I was titrated in a sleep clinic and prescribed a 13 cm optimal on CPAP, I set my S9 Autoset at a max of 13 cm and a min 9 cm and it ended up with a 95% pressure of 11 cm. This is the benefit of an APAP.